sql_prepare.cc

/* Copyright (C) 1995-2002 MySQL AB

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA */

/**
  @file

This file contains the implementation of prepared statements.

When one prepares a statement:

  - Server gets the query from client with command 'COM_STMT_PREPARE';
    in the following format:
    [COM_STMT_PREPARE:1] [query]
  - Parse the query and recognize any parameter markers '?' and
    store its information list in lex->param_list
  - Allocate a new statement for this prepare; and keep this in
    'thd->stmt_map'.
  - Without executing the query, return back to client the total
    number of parameters along with result-set metadata information
    (if any) in the following format:
    @verbatim
    [STMT_ID:4]
    [Column_count:2]
    [Param_count:2]
    [Params meta info (stubs only for now)]  (if Param_count > 0)
    [Columns meta info] (if Column_count > 0)
    @endverbatim

  During prepare the tables used in a statement are opened, but no
  locks are acquired.  Table opening will block any DDL during the
  operation, and we do not need any locks as we neither read nor
  modify any data during prepare.  Tables are closed after prepare
  finishes.

When one executes a statement:

  - Server gets the command 'COM_STMT_EXECUTE' to execute the
    previously prepared query. If there are any parameter markers, then the
    client will send the data in the following format:
    @verbatim
    [COM_STMT_EXECUTE:1]
    [STMT_ID:4]
    [NULL_BITS:(param_count+7)/8)]
    [TYPES_SUPPLIED_BY_CLIENT(0/1):1]
    [[length]data]
    [[length]data] .. [[length]data].
    @endverbatim
    (Note: Except for string/binary types; all other types will not be
    supplied with length field)
  - If it is a first execute or types of parameters were altered by client,
    then setup the conversion routines.
  - Assign parameter items from the supplied data.
  - Execute the query without re-parsing and send back the results
    to client

  During execution of prepared statement tables are opened and locked
  the same way they would for normal (non-prepared) statement
  execution.  Tables are unlocked and closed after the execution.

When one supplies long data for a placeholder:

  - Server gets the long data in pieces with command type
    'COM_STMT_SEND_LONG_DATA'.
  - The packet recieved will have the format as:
    [COM_STMT_SEND_LONG_DATA:1][STMT_ID:4][parameter_number:2][data]
  - data from the packet is appended to the long data value buffer for this
    placeholder.
  - It's up to the client to stop supplying data chunks at any point. The
    server doesn't care; also, the server doesn't notify the client whether
    it got the data or not; if there is any error, then it will be returned
    at statement execute.
*/

#include "mysql_priv.h"
#include "sql_select.h" // for JOIN
#include "sql_cursor.h"
#include "sp_head.h"
#include "sp.h"
#include "sp_cache.h"
#include "probes_mysql.h"
#ifdef EMBEDDED_LIBRARY
/* include MYSQL_BIND headers */
#include <mysql.h>
#else
#include <mysql_com.h>
#endif

/**
  A result class used to send cursor rows using the binary protocol.
*/

class Select_fetch_protocol_binary: public select_send
{
  Protocol_binary protocol;
public:
  Select_fetch_protocol_binary(THD *thd);
  virtual bool send_fields(List<Item> &list, uint flags);
  virtual bool send_data(List<Item> &items);
  virtual bool send_eof();
#ifdef EMBEDDED_LIBRARY
  void begin_dataset()
  {
    protocol.begin_dataset();
  }
#endif
};

/****************************************************************************/

/**
  Prepared_statement: a statement that can contain placeholders.
*/

class Prepared_statement: public Statement
{
public:
  enum flag_values
  {
    IS_IN_USE= 1,
    IS_SQL_PREPARE= 2
  };

  THD *thd;
  Select_fetch_protocol_binary result;
  Item_param **param_array;
  uint param_count;
  uint last_errno;
  uint flags;
  char last_error[MYSQL_ERRMSG_SIZE];
#ifndef EMBEDDED_LIBRARY
  bool (*set_params)(Prepared_statement *st, uchar *data, uchar *data_end,
                     uchar *read_pos, String *expanded_query);
#else
  bool (*set_params_data)(Prepared_statement *st, String *expanded_query);
#endif
  bool (*set_params_from_vars)(Prepared_statement *stmt,
                               List<LEX_STRING>& varnames,
                               String *expanded_query);
public:
  Prepared_statement(THD *thd_arg);
  virtual ~Prepared_statement();
  void setup_set_params();
  virtual Query_arena::Type type() const;
  virtual void cleanup_stmt();
  bool set_name(LEX_STRING *name);
  inline void close_cursor() { delete cursor; cursor= 0; }
  inline bool is_in_use() { return flags & (uint) IS_IN_USE; }
  inline bool is_sql_prepare() const { return flags & (uint) IS_SQL_PREPARE; }
  void set_sql_prepare() { flags|= (uint) IS_SQL_PREPARE; }
  bool prepare(const char *packet, uint packet_length);
  bool execute_loop(String *expanded_query,
                    bool open_cursor,
                    uchar *packet_arg, uchar *packet_end_arg);
  /* Destroy this statement */
  void deallocate();
private:
  /**
    The memory root to allocate parsed tree elements (instances of Item,
    SELECT_LEX and other classes).
  */
  MEM_ROOT main_mem_root;
  /* Version of the stored functions cache at the time of prepare. */
  ulong m_sp_cache_version;
private:
  bool set_db(const char *db, uint db_length);
  bool set_parameters(String *expanded_query,
                      uchar *packet, uchar *packet_end);
  bool execute(String *expanded_query, bool open_cursor);
  bool reprepare();
  bool validate_metadata(Prepared_statement  *copy);
  void swap_prepared_statement(Prepared_statement *copy);
};


/******************************************************************************
  Implementation
******************************************************************************/


inline bool is_param_null(const uchar *pos, ulong param_no)
{
  return pos[param_no/8] & (1 << (param_no & 7));
}

/**
  Find a prepared statement in the statement map by id.

    Try to find a prepared statement and set THD error if it's not found.

  @param thd                thread handle
  @param id                 statement id
  @param where              the place from which this function is called (for
                            error reporting).

  @return
    0 if the statement was not found, a pointer otherwise.
*/

static Prepared_statement *
find_prepared_statement(THD *thd, ulong id)
{
  /*
    To strictly separate namespaces of SQL prepared statements and C API
    prepared statements find() will return 0 if there is a named prepared
    statement with such id.
  */
  Statement *stmt= thd->stmt_map.find(id);

  if (stmt == 0 || stmt->type() != Query_arena::PREPARED_STATEMENT)
    return NULL;

  return (Prepared_statement *) stmt;
}


/**
  Send prepared statement id and metadata to the client after prepare.

  @todo
    Fix this nasty upcast from List<Item_param> to List<Item>

  @return
    0 in case of success, 1 otherwise
*/

#ifndef EMBEDDED_LIBRARY
static bool send_prep_stmt(Prepared_statement *stmt, uint columns)
{
  NET *net= &stmt->thd->net;
  uchar buff[12];
  uint tmp;
  int error;
  THD *thd= stmt->thd;
  DBUG_ENTER("send_prep_stmt");

  buff[0]= 0;                                   /* OK packet indicator */
  int4store(buff+1, stmt->id);
  int2store(buff+5, columns);
  int2store(buff+7, stmt->param_count);
  buff[9]= 0;                                   // Guard against a 4.1 client
  tmp= min(stmt->thd->warning_info->statement_warn_count(), 65535);
  int2store(buff+10, tmp);

  /*
    Send types and names of placeholders to the client
    XXX: fix this nasty upcast from List<Item_param> to List<Item>
  */
  error= my_net_write(net, buff, sizeof(buff));
  if (stmt->param_count && ! error)
  {
    error= thd->protocol_text.send_fields((List<Item> *)
                                          &stmt->lex->param_list,
                                          Protocol::SEND_EOF);
  }
  /* Flag that a response has already been sent */
  thd->stmt_da->disable_status();
  DBUG_RETURN(error);
}
#else
static bool send_prep_stmt(Prepared_statement *stmt,
                           uint columns __attribute__((unused)))
{
  THD *thd= stmt->thd;

  thd->client_stmt_id= stmt->id;
  thd->client_param_count= stmt->param_count;
  thd->clear_error();
  thd->stmt_da->disable_status();

  return 0;
}
#endif /*!EMBEDDED_LIBRARY*/


#ifndef EMBEDDED_LIBRARY

/**
  Read the length of the parameter data and return it back to
  the caller.

    Read data length, position the packet to the first byte after it,
    and return the length to the caller.

  @param packet             a pointer to the data
  @param len                remaining packet length

  @return
    Length of data piece.
*/

static ulong get_param_length(uchar **packet, ulong len)
{
  reg1 uchar *pos= *packet;
  if (len < 1)
    return 0;
  if (*pos < 251)
  {
    (*packet)++;
    return (ulong) *pos;
  }
  if (len < 3)
    return 0;
  if (*pos == 252)
  {
    (*packet)+=3;
    return (ulong) uint2korr(pos+1);
  }
  if (len < 4)
    return 0;
  if (*pos == 253)
  {
    (*packet)+=4;
    return (ulong) uint3korr(pos+1);
  }
  if (len < 5)
    return 0;
  (*packet)+=9; // Must be 254 when here
  /*
    In our client-server protocol all numbers bigger than 2^24
    stored as 8 bytes with uint8korr. Here we always know that
    parameter length is less than 2^4 so don't look at the second
    4 bytes. But still we need to obey the protocol hence 9 in the
    assignment above.
  */
  return (ulong) uint4korr(pos+1);
}
#else
#define get_param_length(packet, len) len
#endif /*!EMBEDDED_LIBRARY*/

/**
  Data conversion routines.

    All these functions read the data from pos, convert it to requested
    type and assign to param; pos is advanced to predefined length.

    Make a note that the NULL handling is examined at first execution
    (i.e. when input types altered) and for all subsequent executions
    we don't read any values for this.

  @param  param             parameter item
  @param  pos               input data buffer
  @param  len               length of data in the buffer
*/

static void set_param_tiny(Item_param *param, uchar **pos, ulong len)
{
#ifndef EMBEDDED_LIBRARY
  if (len < 1)
    return;
#endif
  int8 value= (int8) **pos;
  param->set_int(param->unsigned_flag ? (longlong) ((uint8) value) :
                                        (longlong) value, 4);
  *pos+= 1;
}

static void set_param_short(Item_param *param, uchar **pos, ulong len)
{
  int16 value;
#ifndef EMBEDDED_LIBRARY
  if (len < 2)
    return;
  value= sint2korr(*pos);
#else
  shortget(value, *pos);
#endif
  param->set_int(param->unsigned_flag ? (longlong) ((uint16) value) :
                                        (longlong) value, 6);
  *pos+= 2;
}

static void set_param_int32(Item_param *param, uchar **pos, ulong len)
{
  int32 value;
#ifndef EMBEDDED_LIBRARY
  if (len < 4)
    return;
  value= sint4korr(*pos);
#else
  longget(value, *pos);
#endif
  param->set_int(param->unsigned_flag ? (longlong) ((uint32) value) :
                                        (longlong) value, 11);
  *pos+= 4;
}

static void set_param_int64(Item_param *param, uchar **pos, ulong len)
{
  longlong value;
#ifndef EMBEDDED_LIBRARY
  if (len < 8)
    return;
  value= (longlong) sint8korr(*pos);
#else
  longlongget(value, *pos);
#endif
  param->set_int(value, 21);
  *pos+= 8;
}

static void set_param_float(Item_param *param, uchar **pos, ulong len)
{
  float data;
#ifndef EMBEDDED_LIBRARY
  if (len < 4)
    return;
  float4get(data,*pos);
#else
  floatget(data, *pos);
#endif
  param->set_double((double) data);
  *pos+= 4;
}

static void set_param_double(Item_param *param, uchar **pos, ulong len)
{
  double data;
#ifndef EMBEDDED_LIBRARY
  if (len < 8)
    return;
  float8get(data,*pos);
#else
  doubleget(data, *pos);
#endif
  param->set_double((double) data);
  *pos+= 8;
}

static void set_param_decimal(Item_param *param, uchar **pos, ulong len)
{
  ulong length= get_param_length(pos, len);
  param->set_decimal((char*)*pos, length);
  *pos+= length;
}

#ifndef EMBEDDED_LIBRARY

/*
  Read date/time/datetime parameter values from network (binary
  protocol). See writing counterparts of these functions in
  libmysql.c (store_param_{time,date,datetime}).
*/

/**
  @todo
    Add warning 'Data truncated' here
*/
static void set_param_time(Item_param *param, uchar **pos, ulong len)
{
  MYSQL_TIME tm;
  ulong length= get_param_length(pos, len);

  if (length >= 8)
  {
    uchar *to= *pos;
    uint day;

    tm.neg= (bool) to[0];
    day= (uint) sint4korr(to+1);
    tm.hour=   (uint) to[5] + day * 24;
    tm.minute= (uint) to[6];
    tm.second= (uint) to[7];
    tm.second_part= (length > 8) ? (ulong) sint4korr(to+8) : 0;
    if (tm.hour > 838)
    {
      /* TODO: add warning 'Data truncated' here */
      tm.hour= 838;
      tm.minute= 59;
      tm.second= 59;
    }
    tm.day= tm.year= tm.month= 0;
  }
  else
    set_zero_time(&tm, MYSQL_TIMESTAMP_TIME);
  param->set_time(&tm, MYSQL_TIMESTAMP_TIME,
                  MAX_TIME_WIDTH * MY_CHARSET_BIN_MB_MAXLEN);
  *pos+= length;
}

static void set_param_datetime(Item_param *param, uchar **pos, ulong len)
{
  MYSQL_TIME tm;
  ulong length= get_param_length(pos, len);

  if (length >= 4)
  {
    uchar *to= *pos;

    tm.neg=    0;
    tm.year=   (uint) sint2korr(to);
    tm.month=  (uint) to[2];
    tm.day=    (uint) to[3];
    if (length > 4)
    {
      tm.hour=   (uint) to[4];
      tm.minute= (uint) to[5];
      tm.second= (uint) to[6];
    }
    else
      tm.hour= tm.minute= tm.second= 0;

    tm.second_part= (length > 7) ? (ulong) sint4korr(to+7) : 0;
  }
  else
    set_zero_time(&tm, MYSQL_TIMESTAMP_DATETIME);
  param->set_time(&tm, MYSQL_TIMESTAMP_DATETIME,
                  MAX_DATETIME_WIDTH * MY_CHARSET_BIN_MB_MAXLEN);
  *pos+= length;
}


static void set_param_date(Item_param *param, uchar **pos, ulong len)
{
  MYSQL_TIME tm;
  ulong length= get_param_length(pos, len);

  if (length >= 4)
  {
    uchar *to= *pos;

    tm.year=  (uint) sint2korr(to);
    tm.month=  (uint) to[2];
    tm.day= (uint) to[3];

    tm.hour= tm.minute= tm.second= 0;
    tm.second_part= 0;
    tm.neg= 0;
  }
  else
    set_zero_time(&tm, MYSQL_TIMESTAMP_DATE);
  param->set_time(&tm, MYSQL_TIMESTAMP_DATE,
                  MAX_DATE_WIDTH * MY_CHARSET_BIN_MB_MAXLEN);
  *pos+= length;
}

#else/*!EMBEDDED_LIBRARY*/
/**
  @todo
    Add warning 'Data truncated' here
*/
void set_param_time(Item_param *param, uchar **pos, ulong len)
{
  MYSQL_TIME tm= *((MYSQL_TIME*)*pos);
  tm.hour+= tm.day * 24;
  tm.day= tm.year= tm.month= 0;
  if (tm.hour > 838)
  {
    /* TODO: add warning 'Data truncated' here */
    tm.hour= 838;
    tm.minute= 59;
    tm.second= 59;
  }
  param->set_time(&tm, MYSQL_TIMESTAMP_TIME,
                  MAX_TIME_WIDTH * MY_CHARSET_BIN_MB_MAXLEN);

}

void set_param_datetime(Item_param *param, uchar **pos, ulong len)
{
  MYSQL_TIME tm= *((MYSQL_TIME*)*pos);
  tm.neg= 0;

  param->set_time(&tm, MYSQL_TIMESTAMP_DATETIME,
                  MAX_DATETIME_WIDTH * MY_CHARSET_BIN_MB_MAXLEN);
}

void set_param_date(Item_param *param, uchar **pos, ulong len)
{
  MYSQL_TIME *to= (MYSQL_TIME*)*pos;

  param->set_time(to, MYSQL_TIMESTAMP_DATE,
                  MAX_DATE_WIDTH * MY_CHARSET_BIN_MB_MAXLEN);
}
#endif /*!EMBEDDED_LIBRARY*/


static void set_param_str(Item_param *param, uchar **pos, ulong len)
{
  ulong length= get_param_length(pos, len);
  if (length > len)
    length= len;
  param->set_str((const char *)*pos, length);
  *pos+= length;
}


#undef get_param_length

static void setup_one_conversion_function(THD *thd, Item_param *param,
                                          uchar param_type)
{
  switch (param_type) {
  case MYSQL_TYPE_TINY:
    param->set_param_func= set_param_tiny;
    param->item_type= Item::INT_ITEM;
    param->item_result_type= INT_RESULT;
    break;
  case MYSQL_TYPE_SHORT:
    param->set_param_func= set_param_short;
    param->item_type= Item::INT_ITEM;
    param->item_result_type= INT_RESULT;
    break;
  case MYSQL_TYPE_LONG:
    param->set_param_func= set_param_int32;
    param->item_type= Item::INT_ITEM;
    param->item_result_type= INT_RESULT;
    break;
  case MYSQL_TYPE_LONGLONG:
    param->set_param_func= set_param_int64;
    param->item_type= Item::INT_ITEM;
    param->item_result_type= INT_RESULT;
    break;
  case MYSQL_TYPE_FLOAT:
    param->set_param_func= set_param_float;
    param->item_type= Item::REAL_ITEM;
    param->item_result_type= REAL_RESULT;
    break;
  case MYSQL_TYPE_DOUBLE:
    param->set_param_func= set_param_double;
    param->item_type= Item::REAL_ITEM;
    param->item_result_type= REAL_RESULT;
    break;
  case MYSQL_TYPE_DECIMAL:
  case MYSQL_TYPE_NEWDECIMAL:
    param->set_param_func= set_param_decimal;
    param->item_type= Item::DECIMAL_ITEM;
    param->item_result_type= DECIMAL_RESULT;
    break;
  case MYSQL_TYPE_TIME:
    param->set_param_func= set_param_time;
    param->item_type= Item::STRING_ITEM;
    param->item_result_type= STRING_RESULT;
    break;
  case MYSQL_TYPE_DATE:
    param->set_param_func= set_param_date;
    param->item_type= Item::STRING_ITEM;
    param->item_result_type= STRING_RESULT;
    break;
  case MYSQL_TYPE_DATETIME:
  case MYSQL_TYPE_TIMESTAMP:
    param->set_param_func= set_param_datetime;
    param->item_type= Item::STRING_ITEM;
    param->item_result_type= STRING_RESULT;
    break;
  case MYSQL_TYPE_TINY_BLOB:
  case MYSQL_TYPE_MEDIUM_BLOB:
  case MYSQL_TYPE_LONG_BLOB:
  case MYSQL_TYPE_BLOB:
    param->set_param_func= set_param_str;
    param->value.cs_info.character_set_of_placeholder= &my_charset_bin;
    param->value.cs_info.character_set_client=
      thd->variables.character_set_client;
    DBUG_ASSERT(thd->variables.character_set_client);
    param->value.cs_info.final_character_set_of_str_value= &my_charset_bin;
    param->item_type= Item::STRING_ITEM;
    param->item_result_type= STRING_RESULT;
    break;
  default:
    /*
      The client library ensures that we won't get any other typecodes
      except typecodes above and typecodes for string types. Marking
      label as 'default' lets us to handle malformed packets as well.
    */
    {
      CHARSET_INFO *fromcs= thd->variables.character_set_client;
      CHARSET_INFO *tocs= thd->variables.collation_connection;
      uint32 dummy_offset;

      param->value.cs_info.character_set_of_placeholder= fromcs;
      param->value.cs_info.character_set_client= fromcs;

      /*
        Setup source and destination character sets so that they
        are different only if conversion is necessary: this will
        make later checks easier.
      */
      param->value.cs_info.final_character_set_of_str_value=
        String::needs_conversion(0, fromcs, tocs, &dummy_offset) ?
        tocs : fromcs;
      param->set_param_func= set_param_str;
      /*
        Exact value of max_length is not known unless data is converted to
        charset of connection, so we have to set it later.
      */
      param->item_type= Item::STRING_ITEM;
      param->item_result_type= STRING_RESULT;
    }
  }
  param->param_type= (enum enum_field_types) param_type;
}

#ifndef EMBEDDED_LIBRARY
/**
  Routines to assign parameters from data supplied by the client.

    Update the parameter markers by reading data from the packet and
    and generate a valid query for logging.

  @note
    This function, along with other _with_log functions is called when one of
    binary, slow or general logs is open. Logging of prepared statements in
    all cases is performed by means of conventional queries: if parameter
    data was supplied from C API, each placeholder in the query is
    replaced with its actual value; if we're logging a [Dynamic] SQL
    prepared statement, parameter markers are replaced with variable names.
    Example:
    @verbatim
     mysqld_stmt_prepare("UPDATE t1 SET a=a*1.25 WHERE a=?")
       --> general logs gets [Prepare] UPDATE t1 SET a*1.25 WHERE a=?"
     mysqld_stmt_execute(stmt);
       --> general and binary logs get
                             [Execute] UPDATE t1 SET a*1.25 WHERE a=1"
    @endverbatim

    If a statement has been prepared using SQL syntax:
    @verbatim
     PREPARE stmt FROM "UPDATE t1 SET a=a*1.25 WHERE a=?"
       --> general log gets
                                 [Query]   PREPARE stmt FROM "UPDATE ..."
     EXECUTE stmt USING @a
       --> general log gets
                             [Query]   EXECUTE stmt USING @a;
    @endverbatim

  @retval
    0  if success
  @retval
    1  otherwise
*/

static bool insert_params_with_log(Prepared_statement *stmt, uchar *null_array,
                                   uchar *read_pos, uchar *data_end,
                                   String *query)
{
  THD  *thd= stmt->thd;
  Item_param **begin= stmt->param_array;
  Item_param **end= begin + stmt->param_count;
  uint32 length= 0;
  String str;
  const String *res;
  DBUG_ENTER("insert_params_with_log");

  if (query->copy(stmt->query, stmt->query_length, default_charset_info))
    DBUG_RETURN(1);

  for (Item_param **it= begin; it < end; ++it)
  {
    Item_param *param= *it;
    if (param->state != Item_param::LONG_DATA_VALUE)
    {
      if (is_param_null(null_array, (uint) (it - begin)))
        param->set_null();
      else
      {
        if (read_pos >= data_end)
          DBUG_RETURN(1);
        param->set_param_func(param, &read_pos, (uint) (data_end - read_pos));
        if (param->state == Item_param::NO_VALUE)
          DBUG_RETURN(1);
      }
    }
    res= param->query_val_str(&str);
    if (param->convert_str_value(thd))
      DBUG_RETURN(1);                           /* out of memory */

    if (query->replace(param->pos_in_query+length, 1, *res))
      DBUG_RETURN(1);

    length+= res->length()-1;
  }
  DBUG_RETURN(0);
}


static bool insert_params(Prepared_statement *stmt, uchar *null_array,
                          uchar *read_pos, uchar *data_end,
                          String *expanded_query)
{
  Item_param **begin= stmt->param_array;
  Item_param **end= begin + stmt->param_count;

  DBUG_ENTER("insert_params");

  for (Item_param **it= begin; it < end; ++it)
  {
    Item_param *param= *it;
    if (param->state != Item_param::LONG_DATA_VALUE)
    {
      if (is_param_null(null_array, (uint) (it - begin)))
        param->set_null();
      else
      {
        if (read_pos >= data_end)
          DBUG_RETURN(1);
        param->set_param_func(param, &read_pos, (uint) (data_end - read_pos));
        if (param->state == Item_param::NO_VALUE)
          DBUG_RETURN(1);
      }
    }
    if (param->convert_str_value(stmt->thd))
      DBUG_RETURN(1);                           /* out of memory */
  }
  DBUG_RETURN(0);
}


static bool setup_conversion_functions(Prepared_statement *stmt,
                                       uchar **data, uchar *data_end)
{
  /* skip null bits */
  uchar *read_pos= *data + (stmt->param_count+7) / 8;

  DBUG_ENTER("setup_conversion_functions");

  if (*read_pos++) //types supplied / first execute
  {
    /*
      First execute or types altered by the client, setup the
      conversion routines for all parameters (one time)
    */
    Item_param **it= stmt->param_array;
    Item_param **end= it + stmt->param_count;
    THD *thd= stmt->thd;
    for (; it < end; ++it)
    {
      ushort typecode;
      const uint signed_bit= 1 << 15;

      if (read_pos >= data_end)
        DBUG_RETURN(1);

      typecode= sint2korr(read_pos);
      read_pos+= 2;
      (**it).unsigned_flag= test(typecode & signed_bit);
      setup_one_conversion_function(thd, *it, (uchar) (typecode & ~signed_bit));
    }
  }
  *data= read_pos;
  DBUG_RETURN(0);
}

#else

/**
  Embedded counterparts of parameter assignment routines.

    The main difference between the embedded library and the server is
    that in embedded case we don't serialize/deserialize parameters data.

    Additionally, for unknown reason, the client-side flag raised for
    changed types of placeholders is ignored and we simply setup conversion
    functions at each execute (TODO: fix).
*/

static bool emb_insert_params(Prepared_statement *stmt, String *expanded_query)
{
  THD *thd= stmt->thd;
  Item_param **it= stmt->param_array;
  Item_param **end= it + stmt->param_count;
  MYSQL_BIND *client_param= stmt->thd->client_params;

  DBUG_ENTER("emb_insert_params");

  for (; it < end; ++it, ++client_param)
  {
    Item_param *param= *it;
    setup_one_conversion_function(thd, param, client_param->buffer_type);
    if (param->state != Item_param::LONG_DATA_VALUE)
    {
      if (*client_param->is_null)
        param->set_null();
      else
      {
        uchar *buff= (uchar*) client_param->buffer;
        param->unsigned_flag= client_param->is_unsigned;
        param->set_param_func(param, &buff,
                              client_param->length ?
                              *client_param->length :
                              client_param->buffer_length);
        if (param->state == Item_param::NO_VALUE)
          DBUG_RETURN(1);
      }
    }
    if (param->convert_str_value(thd))
      DBUG_RETURN(1);                           /* out of memory */
  }
  DBUG_RETURN(0);
}


static bool emb_insert_params_with_log(Prepared_statement *stmt,
                                       String *query)
{
  THD *thd= stmt->thd;
  Item_param **it= stmt->param_array;
  Item_param **end= it + stmt->param_count;
  MYSQL_BIND *client_param= thd->client_params;

  String str;
  const String *res;
  uint32 length= 0;

  DBUG_ENTER("emb_insert_params_with_log");

  if (query->copy(stmt->query, stmt->query_length, default_charset_info))
    DBUG_RETURN(1);

  for (; it < end; ++it, ++client_param)
  {
    Item_param *param= *it;
    setup_one_conversion_function(thd, param, client_param->buffer_type);
    if (param->state != Item_param::LONG_DATA_VALUE)
    {
      if (*client_param->is_null)
        param->set_null();
      else
      {
        uchar *buff= (uchar*)client_param->buffer;
        param->unsigned_flag= client_param->is_unsigned;
        param->set_param_func(param, &buff,
                              client_param->length ?
                              *client_param->length :
                              client_param->buffer_length);
        if (param->state == Item_param::NO_VALUE)
          DBUG_RETURN(1);
      }
    }
    res= param->query_val_str(&str);
    if (param->convert_str_value(thd))
      DBUG_RETURN(1);                           /* out of memory */

    if (query->replace(param->pos_in_query+length, 1, *res))
      DBUG_RETURN(1);

    length+= res->length()-1;
  }
  DBUG_RETURN(0);
}

#endif /*!EMBEDDED_LIBRARY*/

/**
  Setup data conversion routines using an array of parameter
  markers from the original prepared statement.
  Swap the parameter data of the original prepared
  statement to the new one.

  Used only when we re-prepare a prepared statement.
  There are two reasons for this function to exist:

  1) In the binary client/server protocol, parameter metadata
  is sent only at first execute. Consequently, if we need to
  reprepare a prepared statement at a subsequent execution,
  we may not have metadata information in the packet.
  In that case we use the parameter array of the original
  prepared statement to setup parameter types of the new
  prepared statement.

  2) In the binary client/server protocol, we may supply
  long data in pieces. When the last piece is supplied,
  we assemble the pieces and convert them from client
  character set to the connection character set. After
  that the parameter value is only available inside
  the parameter, the original pieces are lost, and thus
  we can only assign the corresponding parameter of the
  reprepared statement from the original value.

  @param[out]  param_array_dst  parameter markers of the new statement
  @param[in]   param_array_src  parameter markers of the original
                                statement
  @param[in]   param_count      total number of parameters. Is the
                                same in src and dst arrays, since
                                the statement query is the same

  @return this function never fails
*/

static void
swap_parameter_array(Item_param **param_array_dst,
                     Item_param **param_array_src,
                     uint param_count)
{
  Item_param **dst= param_array_dst;
  Item_param **src= param_array_src;
  Item_param **end= param_array_dst + param_count;

  for (; dst < end; ++src, ++dst)
    (*dst)->set_param_type_and_swap_value(*src);
}


/**
  Assign prepared statement parameters from user variables.

  @param stmt      Statement
  @param varnames  List of variables. Caller must ensure that number
                   of variables in the list is equal to number of statement
                   parameters
  @param query     Ignored
*/

static bool insert_params_from_vars(Prepared_statement *stmt,
                                    List<LEX_STRING>& varnames,
                                    String *query __attribute__((unused)))
{
  Item_param **begin= stmt->param_array;
  Item_param **end= begin + stmt->param_count;
  user_var_entry *entry;
  LEX_STRING *varname;
  List_iterator<LEX_STRING> var_it(varnames);
  DBUG_ENTER("insert_params_from_vars");

  for (Item_param **it= begin; it < end; ++it)
  {
    Item_param *param= *it;
    varname= var_it++;
    entry= (user_var_entry*)hash_search(&stmt->thd->user_vars,
                                        (uchar*) varname->str,
                                         varname->length);
    if (param->set_from_user_var(stmt->thd, entry) ||
        param->convert_str_value(stmt->thd))
      DBUG_RETURN(1);
  }
  DBUG_RETURN(0);
}


/**
  Do the same as insert_params_from_vars but also construct query text for
  binary log.

  @param stmt      Prepared statement
  @param varnames  List of variables. Caller must ensure that number of
                   variables in the list is equal to number of statement
                   parameters
  @param query     The query with parameter markers replaced with corresponding
                   user variables that were used to execute the query.
*/

static bool insert_params_from_vars_with_log(Prepared_statement *stmt,
                                             List<LEX_STRING>& varnames,
                                             String *query)
{
  Item_param **begin= stmt->param_array;
  Item_param **end= begin + stmt->param_count;
  user_var_entry *entry;
  LEX_STRING *varname;
  List_iterator<LEX_STRING> var_it(varnames);
  String buf;
  const String *val;
  uint32 length= 0;
  THD *thd= stmt->thd;

  DBUG_ENTER("insert_params_from_vars");

  if (query->copy(stmt->query, stmt->query_length, default_charset_info))
    DBUG_RETURN(1);

  for (Item_param **it= begin; it < end; ++it)
  {
    Item_param *param= *it;
    varname= var_it++;

    entry= (user_var_entry *) hash_search(&thd->user_vars, (uchar*) varname->str,
                                          varname->length);
    /*
      We have to call the setup_one_conversion_function() here to set
      the parameter's members that might be needed further
      (e.g. value.cs_info.character_set_client is used in the query_val_str()).
    */
    setup_one_conversion_function(thd, param, param->param_type);
    if (param->set_from_user_var(thd, entry))
      DBUG_RETURN(1);
    val= param->query_val_str(&buf);

    if (param->convert_str_value(thd))
      DBUG_RETURN(1);                           /* out of memory */

    if (query->replace(param->pos_in_query+length, 1, *val))
      DBUG_RETURN(1);
    length+= val->length()-1;
  }
  DBUG_RETURN(0);
}

/**
  Validate INSERT statement.

  @param stmt               prepared statement
  @param tables             global/local table list

  @retval
    FALSE             success
  @retval
    TRUE              error, error message is set in THD
*/

static bool mysql_test_insert(Prepared_statement *stmt,
                              TABLE_LIST *table_list,
                              List<Item> &fields,
                              List<List_item> &values_list,
                              List<Item> &update_fields,
                              List<Item> &update_values,
                              enum_duplicates duplic)
{
  THD *thd= stmt->thd;
  List_iterator_fast<List_item> its(values_list);
  List_item *values;
  DBUG_ENTER("mysql_test_insert");

  if (insert_precheck(thd, table_list))
    goto error;

  /*
    open temporary memory pool for temporary data allocated by derived
    tables & preparation procedure
    Note that this is done without locks (should not be needed as we will not
    access any data here)
    If we would use locks, then we have to ensure we are not using
    TL_WRITE_DELAYED as having two such locks can cause table corruption.
  */
  if (open_normal_and_derived_tables(thd, table_list, 0))
    goto error;

  if ((values= its++))
  {
    uint value_count;
    ulong counter= 0;
    Item *unused_conds= 0;

    if (table_list->table)
    {
      // don't allocate insert_values
      table_list->table->insert_values=(uchar *)1;
    }

    if (mysql_prepare_insert(thd, table_list, table_list->table,
                             fields, values, update_fields, update_values,
                             duplic, &unused_conds, FALSE, FALSE, FALSE))
      goto error;

    value_count= values->elements;
    its.rewind();

    if (table_list->lock_type == TL_WRITE_DELAYED &&
        !(table_list->table->file->ha_table_flags() & HA_CAN_INSERT_DELAYED))
    {
      my_error(ER_DELAYED_NOT_SUPPORTED, MYF(0), (table_list->view ?
                                                  table_list->view_name.str :
                                                  table_list->table_name));
      goto error;
    }
    while ((values= its++))
    {
      counter++;
      if (values->elements != value_count)
      {
        my_error(ER_WRONG_VALUE_COUNT_ON_ROW, MYF(0), counter);
        goto error;
      }
      if (setup_fields(thd, 0, *values, MARK_COLUMNS_NONE, 0, 0))
        goto error;
    }
  }
  DBUG_RETURN(FALSE);

error:
  /* insert_values is cleared in open_table */
  DBUG_RETURN(TRUE);
}


/**
  Validate UPDATE statement.

  @param stmt               prepared statement
  @param tables             list of tables used in this query

  @todo
    - here we should send types of placeholders to the client.

  @retval
    0                 success
  @retval
    1                 error, error message is set in THD
  @retval
    2                 convert to multi_update
*/

static int mysql_test_update(Prepared_statement *stmt,
                              TABLE_LIST *table_list)
{
  int res;
  THD *thd= stmt->thd;
  uint table_count= 0;
  SELECT_LEX *select= &stmt->lex->select_lex;
#ifndef NO_EMBEDDED_ACCESS_CHECKS
  uint          want_privilege;
#endif
  DBUG_ENTER("mysql_test_update");

  if (update_precheck(thd, table_list) ||
      open_tables(thd, &table_list, &table_count, 0))
    goto error;

  if (table_list->multitable_view)
  {
    DBUG_ASSERT(table_list->view != 0);
    DBUG_PRINT("info", ("Switch to multi-update"));
    /* pass counter value */
    thd->lex->table_count= table_count;
    /* convert to multiupdate */
    DBUG_RETURN(2);
  }

  /*
    thd->fill_derived_tables() is false here for sure (because it is
    preparation of PS, so we even do not check it).
  */
  if (mysql_handle_derived(thd->lex, &mysql_derived_prepare))
    goto error;

#ifndef NO_EMBEDDED_ACCESS_CHECKS
  /* Force privilege re-checking for views after they have been opened. */
  want_privilege= (table_list->view ? UPDATE_ACL :
                   table_list->grant.want_privilege);
#endif

  if (mysql_prepare_update(thd, table_list, &select->where,
                           select->order_list.elements,
                           (ORDER *) select->order_list.first))
    goto error;

#ifndef NO_EMBEDDED_ACCESS_CHECKS
  table_list->grant.want_privilege= want_privilege;
  table_list->table->grant.want_privilege= want_privilege;
  table_list->register_want_access(want_privilege);
#endif
  thd->lex->select_lex.no_wrap_view_item= TRUE;
  res= setup_fields(thd, 0, select->item_list, MARK_COLUMNS_READ, 0, 0);
  thd->lex->select_lex.no_wrap_view_item= FALSE;
  if (res)
    goto error;
#ifndef NO_EMBEDDED_ACCESS_CHECKS
  /* Check values */
  table_list->grant.want_privilege=
  table_list->table->grant.want_privilege=
    (SELECT_ACL & ~table_list->table->grant.privilege);
  table_list->register_want_access(SELECT_ACL);
#endif
  if (setup_fields(thd, 0, stmt->lex->value_list, MARK_COLUMNS_NONE, 0, 0))
    goto error;
  /* TODO: here we should send types of placeholders to the client. */
  DBUG_RETURN(0);
error:
  DBUG_RETURN(1);
}


/**
  Validate DELETE statement.

  @param stmt               prepared statement
  @param tables             list of tables used in this query

  @retval
    FALSE             success
  @retval
    TRUE              error, error message is set in THD
*/

static bool mysql_test_delete(Prepared_statement *stmt,
                              TABLE_LIST *table_list)
{
  THD *thd= stmt->thd;
  LEX *lex= stmt->lex;
  DBUG_ENTER("mysql_test_delete");

  if (delete_precheck(thd, table_list) ||
      open_normal_and_derived_tables(thd, table_list, 0))
    goto error;

  if (!table_list->table)
  {
    my_error(ER_VIEW_DELETE_MERGE_VIEW, MYF(0),
             table_list->view_db.str, table_list->view_name.str);
    goto error;
  }

  DBUG_RETURN(mysql_prepare_delete(thd, table_list, &lex->select_lex.where));
error:
  DBUG_RETURN(TRUE);
}


/**
  Validate SELECT statement.

    In case of success, if this query is not EXPLAIN, send column list info
    back to the client.

  @param stmt               prepared statement
  @param tables             list of tables used in the query

  @retval
    0                 success
  @retval
    1                 error, error message is set in THD
  @retval
    2                 success, and statement metadata has been sent
*/

static int mysql_test_select(Prepared_statement *stmt,
                             TABLE_LIST *tables)
{
  THD *thd= stmt->thd;
  LEX *lex= stmt->lex;
  SELECT_LEX_UNIT *unit= &lex->unit;
  DBUG_ENTER("mysql_test_select");

  lex->select_lex.context.resolve_in_select_list= TRUE;

  ulong privilege= lex->exchange ? SELECT_ACL | FILE_ACL : SELECT_ACL;
  if (tables)
  {
    if (check_table_access(thd, privilege, tables, UINT_MAX, FALSE))
      goto error;
  }
  else if (check_access(thd, privilege, any_db,0,0,0,0))
    goto error;

  if (!lex->result && !(lex->result= new (stmt->mem_root) select_send))
  {
    my_error(ER_OUTOFMEMORY, MYF(0), sizeof(select_send));
    goto error;
  }

  if (open_normal_and_derived_tables(thd, tables, 0))
    goto error;

  thd->used_tables= 0;                        // Updated by setup_fields

  /*
    JOIN::prepare calls
    It is not SELECT COMMAND for sure, so setup_tables will be called as
    usual, and we pass 0 as setup_tables_done_option
  */
  if (unit->prepare(thd, 0, 0))
    goto error;
  if (!lex->describe && !stmt->is_sql_prepare())
  {
    /* Make copy of item list, as change_columns may change it */
    List<Item> fields(lex->select_lex.item_list);

    /* Change columns if a procedure like analyse() */
    if (unit->last_procedure && unit->last_procedure->change_columns(fields))
      goto error;

    /*
      We can use lex->result as it should've been prepared in
      unit->prepare call above.
    */
    if (send_prep_stmt(stmt, lex->result->field_count(fields)) ||
        lex->result->send_fields(fields, Protocol::SEND_EOF) ||
        thd->protocol->flush())
      goto error;
    DBUG_RETURN(2);
  }
  DBUG_RETURN(0);
error:
  DBUG_RETURN(1);
}


/**
  Validate and prepare for execution DO statement expressions.

  @param stmt               prepared statement
  @param tables             list of tables used in this query
  @param values             list of expressions

  @retval
    FALSE             success
  @retval
    TRUE              error, error message is set in THD
*/

static bool mysql_test_do_fields(Prepared_statement *stmt,
                                TABLE_LIST *tables,
                                List<Item> *values)
{
  THD *thd= stmt->thd;

  DBUG_ENTER("mysql_test_do_fields");
  if (tables && check_table_access(thd, SELECT_ACL, tables, UINT_MAX, FALSE))
    DBUG_RETURN(TRUE);

  if (open_normal_and_derived_tables(thd, tables, 0))
    DBUG_RETURN(TRUE);
  DBUG_RETURN(setup_fields(thd, 0, *values, MARK_COLUMNS_NONE, 0, 0));
}


/**
  Validate and prepare for execution SET statement expressions.

  @param stmt               prepared statement
  @param tables             list of tables used in this query
  @param values             list of expressions

  @retval
    FALSE             success
  @retval
    TRUE              error, error message is set in THD
*/

static bool mysql_test_set_fields(Prepared_statement *stmt,
                                  TABLE_LIST *tables,
                                  List<set_var_base> *var_list)
{
  DBUG_ENTER("mysql_test_set_fields");
  List_iterator_fast<set_var_base> it(*var_list);
  THD *thd= stmt->thd;
  set_var_base *var;

  if ((tables && check_table_access(thd, SELECT_ACL, tables, UINT_MAX, FALSE)) 
      || open_normal_and_derived_tables(thd, tables, 0))
    goto error;

  while ((var= it++))
  {
    if (var->light_check(thd))
      goto error;
  }
  DBUG_RETURN(FALSE);
error:
  DBUG_RETURN(TRUE);
}


/**
  Validate and prepare for execution CALL statement expressions.

  @param stmt               prepared statement
  @param tables             list of tables used in this query
  @param value_list         list of expressions

  @retval FALSE             success
  @retval TRUE              error, error message is set in THD
*/

static bool mysql_test_call_fields(Prepared_statement *stmt,
                                   TABLE_LIST *tables,
                                   List<Item> *value_list)
{
  DBUG_ENTER("mysql_test_call_fields");

  List_iterator<Item> it(*value_list);
  THD *thd= stmt->thd;
  Item *item;

  if ((tables && check_table_access(thd, SELECT_ACL, tables, UINT_MAX, FALSE)) ||
      open_normal_and_derived_tables(thd, tables, 0))
    goto err;

  while ((item= it++))
  {
    if ((!item->fixed && item->fix_fields(thd, it.ref())) ||
        item->check_cols(1))
      goto err;
  }
  DBUG_RETURN(FALSE);
err:
  DBUG_RETURN(TRUE);
}


/**
  Check internal SELECT of the prepared command.

  @param stmt                      prepared statement
  @param specific_prepare          function of command specific prepare
  @param setup_tables_done_option  options to be passed to LEX::unit.prepare()

  @note
    This function won't directly open tables used in select. They should
    be opened either by calling function (and in this case you probably
    should use select_like_stmt_test_with_open()) or by
    "specific_prepare" call (like this happens in case of multi-update).

  @retval
    FALSE                success
  @retval
    TRUE                 error, error message is set in THD
*/

static bool select_like_stmt_test(Prepared_statement *stmt,
                                  int (*specific_prepare)(THD *thd),
                                  ulong setup_tables_done_option)
{
  DBUG_ENTER("select_like_stmt_test");
  THD *thd= stmt->thd;
  LEX *lex= stmt->lex;

  lex->select_lex.context.resolve_in_select_list= TRUE;

  if (specific_prepare && (*specific_prepare)(thd))
    DBUG_RETURN(TRUE);

  thd->used_tables= 0;                        // Updated by setup_fields

  /* Calls JOIN::prepare */
  DBUG_RETURN(lex->unit.prepare(thd, 0, setup_tables_done_option));
}

/**
  Check internal SELECT of the prepared command (with opening of used
  tables).

  @param stmt                      prepared statement
  @param tables                    list of tables to be opened
                                   before calling specific_prepare function
  @param specific_prepare          function of command specific prepare
  @param setup_tables_done_option  options to be passed to LEX::unit.prepare()

  @retval
    FALSE                success
  @retval
    TRUE                 error
*/

static bool
select_like_stmt_test_with_open(Prepared_statement *stmt,
                                TABLE_LIST *tables,
                                int (*specific_prepare)(THD *thd),
                                ulong setup_tables_done_option)
{
  DBUG_ENTER("select_like_stmt_test_with_open");

  /*
    We should not call LEX::unit.cleanup() after this
    open_normal_and_derived_tables() call because we don't allow
    prepared EXPLAIN yet so derived tables will clean up after
    themself.
  */
  if (open_normal_and_derived_tables(stmt->thd, tables, 0))
    DBUG_RETURN(TRUE);

  DBUG_RETURN(select_like_stmt_test(stmt, specific_prepare,
                                    setup_tables_done_option));
}


/**
  Validate and prepare for execution CREATE TABLE statement.

  @param stmt               prepared statement
  @param tables             list of tables used in this query

  @retval
    FALSE             success
  @retval
    TRUE              error, error message is set in THD
*/

static bool mysql_test_create_table(Prepared_statement *stmt)
{
  DBUG_ENTER("mysql_test_create_table");
  THD *thd= stmt->thd;
  LEX *lex= stmt->lex;
  SELECT_LEX *select_lex= &lex->select_lex;
  bool res= FALSE;
  /* Skip first table, which is the table we are creating */
  bool link_to_local;
  TABLE_LIST *create_table= lex->unlink_first_table(&link_to_local);
  TABLE_LIST *tables= lex->query_tables;

  if (create_table_precheck(thd, tables, create_table))
    DBUG_RETURN(TRUE);

  if (select_lex->item_list.elements)
  {
    if (!(lex->create_info.options & HA_LEX_CREATE_TMP_TABLE))
    {
      lex->link_first_table_back(create_table, link_to_local);
      create_table->create= TRUE;
    }

    if (open_normal_and_derived_tables(stmt->thd, lex->query_tables, 0))
      DBUG_RETURN(TRUE);

    if (!(lex->create_info.options & HA_LEX_CREATE_TMP_TABLE))
      create_table= lex->unlink_first_table(&link_to_local);

    select_lex->context.resolve_in_select_list= TRUE;

    res= select_like_stmt_test(stmt, 0, 0);
  }
  else if (lex->create_info.options & HA_LEX_CREATE_TABLE_LIKE)
  {
    /*
      Check that the source table exist, and also record
      its metadata version. Even though not strictly necessary,
      we validate metadata of all CREATE TABLE statements,
      which keeps metadata validation code simple.
    */
    if (open_normal_and_derived_tables(stmt->thd, lex->query_tables, 0))
      DBUG_RETURN(TRUE);
  }

  /* put tables back for PS rexecuting */
  lex->link_first_table_back(create_table, link_to_local);
  DBUG_RETURN(res);
}


/**
  @brief Validate and prepare for execution CREATE VIEW statement

  @param stmt prepared statement

  @note This function handles create view commands.

  @retval FALSE Operation was a success.
  @retval TRUE An error occured.
*/

static bool mysql_test_create_view(Prepared_statement *stmt)
{
  DBUG_ENTER("mysql_test_create_view");
  THD *thd= stmt->thd;
  LEX *lex= stmt->lex;
  bool res= TRUE;
  /* Skip first table, which is the view we are creating */
  bool link_to_local;
  TABLE_LIST *view= lex->unlink_first_table(&link_to_local);
  TABLE_LIST *tables= lex->query_tables;

  if (create_view_precheck(thd, tables, view, lex->create_view_mode))
    goto err;

  if (open_normal_and_derived_tables(thd, tables, 0))
    goto err;

  lex->view_prepare_mode= 1;
  res= select_like_stmt_test(stmt, 0, 0);

err:
  /* put view back for PS rexecuting */
  lex->link_first_table_back(view, link_to_local);
  DBUG_RETURN(res);
}


/*
  Validate and prepare for execution a multi update statement.

  @param stmt               prepared statement
  @param tables             list of tables used in this query
  @param converted          converted to multi-update from usual update

  @retval
    FALSE             success
  @retval
    TRUE              error, error message is set in THD
*/

static bool mysql_test_multiupdate(Prepared_statement *stmt,
                                  TABLE_LIST *tables,
                                  bool converted)
{
  /* if we switched from normal update, rights are checked */
  if (!converted && multi_update_precheck(stmt->thd, tables))
    return TRUE;

  return select_like_stmt_test(stmt, &mysql_multi_update_prepare,
                               OPTION_SETUP_TABLES_DONE);
}


/**
  Validate and prepare for execution a multi delete statement.

  @param stmt               prepared statement
  @param tables             list of tables used in this query

  @retval
    FALSE             success
  @retval
    TRUE              error, error message in THD is set.
*/

static bool mysql_test_multidelete(Prepared_statement *stmt,
                                  TABLE_LIST *tables)
{
  stmt->thd->lex->current_select= &stmt->thd->lex->select_lex;
  if (add_item_to_list(stmt->thd, new Item_null()))
  {
    my_error(ER_OUTOFMEMORY, MYF(0), 0);
    goto error;
  }

  if (multi_delete_precheck(stmt->thd, tables) ||
      select_like_stmt_test_with_open(stmt, tables,
                                      &mysql_multi_delete_prepare,
                                      OPTION_SETUP_TABLES_DONE))
    goto error;
  if (!tables->table)
  {
    my_error(ER_VIEW_DELETE_MERGE_VIEW, MYF(0),
             tables->view_db.str, tables->view_name.str);
    goto error;
  }
  return FALSE;
error:
  return TRUE;
}


/**
  Wrapper for mysql_insert_select_prepare, to make change of local tables
  after open_normal_and_derived_tables() call.

  @param thd                thread handle

  @note
    We need to remove the first local table after
    open_normal_and_derived_tables(), because mysql_handle_derived
    uses local tables lists.
*/

static int mysql_insert_select_prepare_tester(THD *thd)
{
  SELECT_LEX *first_select= &thd->lex->select_lex;
  TABLE_LIST *second_table= ((TABLE_LIST*)first_select->table_list.first)->
    next_local;

  /* Skip first table, which is the table we are inserting in */
  first_select->table_list.first= (uchar *) second_table;
  thd->lex->select_lex.context.table_list=
    thd->lex->select_lex.context.first_name_resolution_table= second_table;

  return mysql_insert_select_prepare(thd);
}


/**
  Validate and prepare for execution INSERT ... SELECT statement.

  @param stmt               prepared statement
  @param tables             list of tables used in this query

  @retval
    FALSE             success
  @retval
    TRUE              error, error message is set in THD
*/

static bool mysql_test_insert_select(Prepared_statement *stmt,
                                     TABLE_LIST *tables)
{
  int res;
  LEX *lex= stmt->lex;
  TABLE_LIST *first_local_table;

  if (tables->table)
  {
    // don't allocate insert_values
    tables->table->insert_values=(uchar *)1;
  }

  if (insert_precheck(stmt->thd, tables))
    return 1;

  /* store it, because mysql_insert_select_prepare_tester change it */
  first_local_table= (TABLE_LIST *)lex->select_lex.table_list.first;
  DBUG_ASSERT(first_local_table != 0);

  res=
    select_like_stmt_test_with_open(stmt, tables,
                                    &mysql_insert_select_prepare_tester,
                                    OPTION_SETUP_TABLES_DONE);
  /* revert changes  made by mysql_insert_select_prepare_tester */
  lex->select_lex.table_list.first= (uchar*) first_local_table;
  return res;
}


/**
  Perform semantic analysis of the parsed tree and send a response packet
  to the client.

    This function
    - opens all tables and checks access rights
    - validates semantics of statement columns and SQL functions
      by calling fix_fields.

  @param stmt               prepared statement

  @retval
    FALSE             success, statement metadata is sent to client
  @retval
    TRUE              error, error message is set in THD (but not sent)
*/

static bool check_prepared_statement(Prepared_statement *stmt)
{
  THD *thd= stmt->thd;
  LEX *lex= stmt->lex;
  SELECT_LEX *select_lex= &lex->select_lex;
  TABLE_LIST *tables;
  enum enum_sql_command sql_command= lex->sql_command;
  int res= 0;
  DBUG_ENTER("check_prepared_statement");
  DBUG_PRINT("enter",("command: %d  param_count: %u",
                      sql_command, stmt->param_count));

  lex->first_lists_tables_same();
  tables= lex->query_tables;

  /* set context for commands which do not use setup_tables */
  lex->select_lex.context.resolve_in_table_list_only(select_lex->
                                                     get_table_list());

  /* Reset warning count for each query that uses tables */
  if (tables)
    thd->warning_info->opt_clear_warning_info(thd->query_id);

  switch (sql_command) {
  case SQLCOM_REPLACE:
  case SQLCOM_INSERT:
    res= mysql_test_insert(stmt, tables, lex->field_list,
                           lex->many_values,
                           lex->update_list, lex->value_list,
                           lex->duplicates);
    break;

  case SQLCOM_UPDATE:
    res= mysql_test_update(stmt, tables);
    /* mysql_test_update returns 2 if we need to switch to multi-update */
    if (res != 2)
      break;

  case SQLCOM_UPDATE_MULTI:
    res= mysql_test_multiupdate(stmt, tables, res == 2);
    break;

  case SQLCOM_DELETE:
    res= mysql_test_delete(stmt, tables);
    break;
  /* The following allow WHERE clause, so they must be tested like SELECT */
  case SQLCOM_SHOW_DATABASES:
  case SQLCOM_SHOW_TABLES:
  case SQLCOM_SHOW_TRIGGERS:
  case SQLCOM_SHOW_EVENTS:
  case SQLCOM_SHOW_OPEN_TABLES:
  case SQLCOM_SHOW_FIELDS:
  case SQLCOM_SHOW_KEYS:
  case SQLCOM_SHOW_COLLATIONS:
  case SQLCOM_SHOW_CHARSETS:
  case SQLCOM_SHOW_VARIABLES:
  case SQLCOM_SHOW_STATUS:
  case SQLCOM_SHOW_TABLE_STATUS:
  case SQLCOM_SHOW_STATUS_PROC:
  case SQLCOM_SHOW_STATUS_FUNC:
  case SQLCOM_SELECT:
    res= mysql_test_select(stmt, tables);
    if (res == 2)
    {
      /* Statement and field info has already been sent */
      DBUG_RETURN(FALSE);
    }
    break;
  case SQLCOM_CREATE_TABLE:
    res= mysql_test_create_table(stmt);
    break;

  case SQLCOM_CREATE_VIEW:
    if (lex->create_view_mode == VIEW_ALTER)
    {
      my_message(ER_UNSUPPORTED_PS, ER(ER_UNSUPPORTED_PS), MYF(0));
      goto error;
    }
    res= mysql_test_create_view(stmt);
    break;
  case SQLCOM_DO:
    res= mysql_test_do_fields(stmt, tables, lex->insert_list);
    break;

  case SQLCOM_CALL:
    res= mysql_test_call_fields(stmt, tables, &lex->value_list);
    break;
  case SQLCOM_SET_OPTION:
    res= mysql_test_set_fields(stmt, tables, &lex->var_list);
    break;

  case SQLCOM_DELETE_MULTI:
    res= mysql_test_multidelete(stmt, tables);
    break;

  case SQLCOM_INSERT_SELECT:
  case SQLCOM_REPLACE_SELECT:
    res= mysql_test_insert_select(stmt, tables);
    break;

    /*
      Note that we don't need to have cases in this list if they are
      marked with CF_STATUS_COMMAND in sql_command_flags
    */
  case SQLCOM_SHOW_PROCESSLIST:
  case SQLCOM_SHOW_STORAGE_ENGINES:
  case SQLCOM_SHOW_PRIVILEGES:
  case SQLCOM_SHOW_COLUMN_TYPES:
  case SQLCOM_SHOW_ENGINE_LOGS:
  case SQLCOM_SHOW_ENGINE_STATUS:
  case SQLCOM_SHOW_ENGINE_MUTEX:
  case SQLCOM_SHOW_CREATE_DB:
  case SQLCOM_SHOW_GRANTS:
  case SQLCOM_SHOW_BINLOG_EVENTS:
  case SQLCOM_SHOW_MASTER_STAT:
  case SQLCOM_SHOW_SLAVE_STAT:
  case SQLCOM_SHOW_CREATE_PROC:
  case SQLCOM_SHOW_CREATE_FUNC:
  case SQLCOM_SHOW_CREATE_EVENT:
  case SQLCOM_SHOW_CREATE_TRIGGER:
  case SQLCOM_SHOW_CREATE:
  case SQLCOM_SHOW_PROC_CODE:
  case SQLCOM_SHOW_FUNC_CODE:
  case SQLCOM_SHOW_AUTHORS:
  case SQLCOM_SHOW_CONTRIBUTORS:
  case SQLCOM_SHOW_WARNS:
  case SQLCOM_SHOW_ERRORS:
  case SQLCOM_SHOW_BINLOGS:
  case SQLCOM_DROP_TABLE:
  case SQLCOM_RENAME_TABLE:
  case SQLCOM_ALTER_TABLE:
  case SQLCOM_COMMIT:
  case SQLCOM_CREATE_INDEX:
  case SQLCOM_DROP_INDEX:
  case SQLCOM_ROLLBACK:
  case SQLCOM_TRUNCATE:
  case SQLCOM_DROP_VIEW:
  case SQLCOM_REPAIR:
  case SQLCOM_ANALYZE:
  case SQLCOM_OPTIMIZE:
  case SQLCOM_CHANGE_MASTER:
  case SQLCOM_RESET:
  case SQLCOM_FLUSH:
  case SQLCOM_SLAVE_START:
  case SQLCOM_SLAVE_STOP:
  case SQLCOM_INSTALL_PLUGIN:
  case SQLCOM_UNINSTALL_PLUGIN:
  case SQLCOM_CREATE_DB:
  case SQLCOM_DROP_DB:
  case SQLCOM_ALTER_DB_UPGRADE:
  case SQLCOM_CHECKSUM:
  case SQLCOM_CREATE_USER:
  case SQLCOM_RENAME_USER:
  case SQLCOM_DROP_USER:
  case SQLCOM_ASSIGN_TO_KEYCACHE:
  case SQLCOM_PRELOAD_KEYS:
  case SQLCOM_GRANT:
  case SQLCOM_REVOKE:
  case SQLCOM_KILL:
    break;

  case SQLCOM_PREPARE:
  case SQLCOM_EXECUTE:
  case SQLCOM_DEALLOCATE_PREPARE:
  default:
    /*
      Trivial check of all status commands. This is easier than having
      things in the above case list, as it's less chance for mistakes.
    */
    if (!(sql_command_flags[sql_command] & CF_STATUS_COMMAND))
    {
      /* All other statements are not supported yet. */
      my_message(ER_UNSUPPORTED_PS, ER(ER_UNSUPPORTED_PS), MYF(0));
      goto error;
    }
    break;
  }
  if (res == 0)
    DBUG_RETURN(stmt->is_sql_prepare() ?
                FALSE : (send_prep_stmt(stmt, 0) || thd->protocol->flush()));
error:
  DBUG_RETURN(TRUE);
}

/**
  Initialize array of parameters in statement from LEX.
  (We need to have quick access to items by number in mysql_stmt_get_longdata).
  This is to avoid using malloc/realloc in the parser.
*/

static bool init_param_array(Prepared_statement *stmt)
{
  LEX *lex= stmt->lex;
  if ((stmt->param_count= lex->param_list.elements))
  {
    if (stmt->param_count > (uint) UINT_MAX16)
    {
      /* Error code to be defined in 5.0 */
      my_message(ER_PS_MANY_PARAM, ER(ER_PS_MANY_PARAM), MYF(0));
      return TRUE;
    }
    Item_param **to;
    List_iterator<Item_param> param_iterator(lex->param_list);
    /* Use thd->mem_root as it points at statement mem_root */
    stmt->param_array= (Item_param **)
                       alloc_root(stmt->thd->mem_root,
                                  sizeof(Item_param*) * stmt->param_count);
    if (!stmt->param_array)
      return TRUE;
    for (to= stmt->param_array;
         to < stmt->param_array + stmt->param_count;
         ++to)
    {
      *to= param_iterator++;
    }
  }
  return FALSE;
}


/**
  COM_STMT_PREPARE handler.

    Given a query string with parameter markers, create a prepared
    statement from it and send PS info back to the client.

    If parameter markers are found in the query, then store the information
    using Item_param along with maintaining a list in lex->param_array, so
    that a fast and direct retrieval can be made without going through all
    field items.

  @param packet             query to be prepared
  @param packet_length      query string length, including ignored
                            trailing NULL or quote char.

  @note
    This function parses the query and sends the total number of parameters
    and resultset metadata information back to client (if any), without
    executing the query i.e. without any log/disk writes. This allows the
    queries to be re-executed without re-parsing during execute.

  @return
    none: in case of success a new statement id and metadata is sent
    to the client, otherwise an error message is set in THD.
*/

void mysqld_stmt_prepare(THD *thd, const char *packet, uint packet_length)
{
  Protocol *save_protocol= thd->protocol;
  Prepared_statement *stmt;
  bool error;
  DBUG_ENTER("mysqld_stmt_prepare");

  DBUG_PRINT("prep_query", ("%s", packet));

  /* First of all clear possible warnings from the previous command */
  mysql_reset_thd_for_next_command(thd);

  if (! (stmt= new Prepared_statement(thd)))
    DBUG_VOID_RETURN; /* out of memory: error is set in Sql_alloc */

  if (thd->stmt_map.insert(thd, stmt))
  {
    /*
      The error is set in the insert. The statement itself
      will be also deleted there (this is how the hash works).
    */
    DBUG_VOID_RETURN;
  }

  sp_cache_flush_obsolete(&thd->sp_proc_cache);
  sp_cache_flush_obsolete(&thd->sp_func_cache);

  thd->protocol= &thd->protocol_binary;

  if (!(specialflag & SPECIAL_NO_PRIOR))
    my_pthread_setprio(pthread_self(),QUERY_PRIOR);

  error= stmt->prepare(packet, packet_length);

  if (!(specialflag & SPECIAL_NO_PRIOR))
    my_pthread_setprio(pthread_self(),WAIT_PRIOR);

  if (error)
  {
    /* Statement map deletes statement on erase */
    thd->stmt_map.erase(stmt);
  }

  thd->protocol= save_protocol;

  /* check_prepared_statemnt sends the metadata packet in case of success */
  DBUG_VOID_RETURN;
}

/**
  Get an SQL statement text from a user variable or from plain text.

  If the statement is plain text, just assign the
  pointers, otherwise allocate memory in thd->mem_root and copy
  the contents of the variable, possibly with character
  set conversion.

  @param[in]  lex               main lex
  @param[out] query_len         length of the SQL statement (is set only
    in case of success)

  @retval
    non-zero  success
  @retval
    0         in case of error (out of memory)
*/

static const char *get_dynamic_sql_string(LEX *lex, uint *query_len)
{
  THD *thd= lex->thd;
  char *query_str= 0;

  if (lex->prepared_stmt_code_is_varref)
  {
    /* This is PREPARE stmt FROM or EXECUTE IMMEDIATE @var. */
    String str;
    CHARSET_INFO *to_cs= thd->variables.collation_connection;
    bool needs_conversion;
    user_var_entry *entry;
    String *var_value= &str;
    uint32 unused, len;
    /*
      Convert @var contents to string in connection character set. Although
      it is known that int/real/NULL value cannot be a valid query we still
      convert it for error messages to be uniform.
    */
    if ((entry=
         (user_var_entry*)hash_search(&thd->user_vars,
                                      (uchar*)lex->prepared_stmt_code.str,
                                      lex->prepared_stmt_code.length))
        && entry->value)
    {
      my_bool is_var_null;
      var_value= entry->val_str(&is_var_null, &str, NOT_FIXED_DEC);
      /*
        NULL value of variable checked early as entry->value so here
        we can't get NULL in normal conditions
      */
      DBUG_ASSERT(!is_var_null);
      if (!var_value)
        goto end;
    }
    else
    {
      /*
        variable absent or equal to NULL, so we need to set variable to
        something reasonable to get a readable error message during parsing
      */
      str.set(STRING_WITH_LEN("NULL"), &my_charset_latin1);
    }

    needs_conversion= String::needs_conversion(var_value->length(),
                                               var_value->charset(), to_cs,
                                               &unused);

    len= (needs_conversion ? var_value->length() * to_cs->mbmaxlen :
          var_value->length());
    if (!(query_str= (char*) alloc_root(thd->mem_root, len+1)))
      goto end;

    if (needs_conversion)
    {
      uint dummy_errors;
      len= copy_and_convert(query_str, len, to_cs, var_value->ptr(),
                            var_value->length(), var_value->charset(),
                            &dummy_errors);
    }
    else
      memcpy(query_str, var_value->ptr(), var_value->length());
    query_str[len]= '\0';                       // Safety (mostly for debug)
    *query_len= len;
  }
  else
  {
    query_str= lex->prepared_stmt_code.str;
    *query_len= lex->prepared_stmt_code.length;
  }
end:
  return query_str;
}


/** Init PS/SP specific parse tree members.  */

static void init_stmt_after_parse(LEX *lex)
{
  SELECT_LEX *sl= lex->all_selects_list;
  /*
    Switch off a temporary flag that prevents evaluation of
    subqueries in statement prepare.
  */
  for (; sl; sl= sl->next_select_in_list())
   sl->uncacheable&= ~UNCACHEABLE_PREPARE;
}

/**
  SQLCOM_PREPARE implementation.

    Prepare an SQL prepared statement. This is called from
    mysql_execute_command and should therefore behave like an
    ordinary query (e.g. should not reset any global THD data).

  @param thd     thread handle

  @return
    none: in case of success, OK packet is sent to the client,
    otherwise an error message is set in THD
*/

void mysql_sql_stmt_prepare(THD *thd)
{
  LEX *lex= thd->lex;
  LEX_STRING *name= &lex->prepared_stmt_name;
  Prepared_statement *stmt;
  const char *query;
  uint query_len= 0;
  DBUG_ENTER("mysql_sql_stmt_prepare");

  if ((stmt= (Prepared_statement*) thd->stmt_map.find_by_name(name)))
  {
    /*
      If there is a statement with the same name, remove it. It is ok to
      remove old and fail to insert a new one at the same time.
    */
    if (stmt->is_in_use())
    {
      my_error(ER_PS_NO_RECURSION, MYF(0));
      DBUG_VOID_RETURN;
    }

    stmt->deallocate();
  }

  if (! (query= get_dynamic_sql_string(lex, &query_len)) ||
      ! (stmt= new Prepared_statement(thd)))
  {
    DBUG_VOID_RETURN;                           /* out of memory */
  }

  stmt->set_sql_prepare();

  /* Set the name first, insert should know that this statement has a name */
  if (stmt->set_name(name))
  {
    delete stmt;
    DBUG_VOID_RETURN;
  }

  if (thd->stmt_map.insert(thd, stmt))
  {
    /* The statement is deleted and an error is set if insert fails */
    DBUG_VOID_RETURN;
  }

  if (stmt->prepare(query, query_len))
  {
    /* Statement map deletes the statement on erase */
    thd->stmt_map.erase(stmt);
  }
  else
    my_ok(thd, 0L, 0L, "Statement prepared");

  DBUG_VOID_RETURN;
}

/**
  Reinit prepared statement/stored procedure before execution.

  @todo
    When the new table structure is ready, then have a status bit
    to indicate the table is altered, and re-do the setup_*
    and open the tables back.
*/

void reinit_stmt_before_use(THD *thd, LEX *lex)
{
  SELECT_LEX *sl= lex->all_selects_list;
  DBUG_ENTER("reinit_stmt_before_use");

  /*
    We have to update "thd" pointer in LEX, all its units and in LEX::result,
    since statements which belong to trigger body are associated with TABLE
    object and because of this can be used in different threads.
  */
  lex->thd= thd;

  if (lex->empty_field_list_on_rset)
  {
    lex->empty_field_list_on_rset= 0;
    lex->field_list.empty();
  }
  for (; sl; sl= sl->next_select_in_list())
  {
    if (!sl->first_execution)
    {
      /* remove option which was put by mysql_explain_union() */
      sl->options&= ~SELECT_DESCRIBE;

      /* see unique_table() */
      sl->exclude_from_table_unique_test= FALSE;

      /*
        Copy WHERE, HAVING clause pointers to avoid damaging them
        by optimisation
      */
      if (sl->prep_where)
      {
        sl->where= sl->prep_where->copy_andor_structure(thd);
        sl->where->cleanup();
      }
      if (sl->prep_having)
      {
        sl->having= sl->prep_having->copy_andor_structure(thd);
        sl->having->cleanup();
      }
      DBUG_ASSERT(sl->join == 0);
      ORDER *order;
      /* Fix GROUP list */
      for (order= (ORDER *)sl->group_list.first; order; order= order->next)
        order->item= &order->item_ptr;
      /* Fix ORDER list */
      for (order= (ORDER *)sl->order_list.first; order; order= order->next)
        order->item= &order->item_ptr;
    }
    {
      SELECT_LEX_UNIT *unit= sl->master_unit();
      unit->unclean();
      unit->types.empty();
      /* for derived tables & PS (which can't be reset by Item_subquery) */
      unit->reinit_exec_mechanism();
      unit->set_thd(thd);
    }
  }

  /*
    TODO: When the new table structure is ready, then have a status bit
    to indicate the table is altered, and re-do the setup_*
    and open the tables back.
  */
  /*
    NOTE: We should reset whole table list here including all tables added
    by prelocking algorithm (it is not a problem for substatements since
    they have their own table list).
  */
  for (TABLE_LIST *tables= lex->query_tables;
       tables;
       tables= tables->next_global)
  {
    tables->reinit_before_use(thd);
  }
  /*
    Cleanup of the special case of DELETE t1, t2 FROM t1, t2, t3 ...
    (multi-delete).  We do a full clean up, although at the moment all we
    need to clean in the tables of MULTI-DELETE list is 'table' member.
  */
  for (TABLE_LIST *tables= (TABLE_LIST*) lex->auxiliary_table_list.first;
       tables;
       tables= tables->next_global)
  {
    tables->reinit_before_use(thd);
  }
  lex->current_select= &lex->select_lex;

  /* restore original list used in INSERT ... SELECT */
  if (lex->leaf_tables_insert)
    lex->select_lex.leaf_tables= lex->leaf_tables_insert;

  if (lex->result)
  {
    lex->result->cleanup();
    lex->result->set_thd(thd);
  }
  lex->allow_sum_func= 0;
  lex->in_sum_func= NULL;
  DBUG_VOID_RETURN;
}


/**
  Clears parameters from data left from previous execution or long data.

  @param stmt               prepared statement for which parameters should
                            be reset
*/

static void reset_stmt_params(Prepared_statement *stmt)
{
  Item_param **item= stmt->param_array;
  Item_param **end= item + stmt->param_count;
  for (;item < end ; ++item)
    (**item).reset();
}


/**
  COM_STMT_EXECUTE handler: execute a previously prepared statement.

    If there are any parameters, then replace parameter markers with the
    data supplied from the client, and then execute the statement.
    This function uses binary protocol to send a possible result set
    to the client.

  @param thd                current thread
  @param packet_arg         parameter types and data, if any
  @param packet_length      packet length, including the terminator character.

  @return
    none: in case of success OK packet or a result set is sent to the
    client, otherwise an error message is set in THD.
*/

void mysqld_stmt_execute(THD *thd, char *packet_arg, uint packet_length)
{
  uchar *packet= (uchar*)packet_arg; // GCC 4.0.1 workaround
  ulong stmt_id= uint4korr(packet);
  ulong flags= (ulong) packet[4];
  /* Query text for binary, general or slow log, if any of them is open */
  String expanded_query;
  uchar *packet_end= packet + packet_length;
  Prepared_statement *stmt;
  Protocol *save_protocol= thd->protocol;
  bool open_cursor;
  DBUG_ENTER("mysqld_stmt_execute");

  packet+= 9;                               /* stmt_id + 5 bytes of flags */

  /* First of all clear possible warnings from the previous command */
  mysql_reset_thd_for_next_command(thd);

  if (!(stmt= find_prepared_statement(thd, stmt_id)))
  {
    char llbuf[22];
    my_error(ER_UNKNOWN_STMT_HANDLER, MYF(0), sizeof(llbuf),
             llstr(stmt_id, llbuf), "mysqld_stmt_execute");
    DBUG_VOID_RETURN;
  }

#if defined(ENABLED_PROFILING)
  thd->profiling.set_query_source(stmt->query, stmt->query_length);
#endif
  DBUG_PRINT("exec_query", ("%s", stmt->query));
  DBUG_PRINT("info",("stmt: 0x%lx", (long) stmt));

  sp_cache_flush_obsolete(&thd->sp_proc_cache);
  sp_cache_flush_obsolete(&thd->sp_func_cache);

  open_cursor= test(flags & (ulong) CURSOR_TYPE_READ_ONLY);

  thd->protocol= &thd->protocol_binary;
  stmt->execute_loop(&expanded_query, open_cursor, packet, packet_end);
  thd->protocol= save_protocol;

  /* Close connection socket; for use with client testing (Bug#43560). */
  DBUG_EXECUTE_IF("close_conn_after_stmt_execute", vio_close(thd->net.vio););

  DBUG_VOID_RETURN;

}


/**
  SQLCOM_EXECUTE implementation.

    Execute prepared statement using parameter values from
    lex->prepared_stmt_params and send result to the client using
    text protocol. This is called from mysql_execute_command and
    therefore should behave like an ordinary query (e.g. not change
    global THD data, such as warning count, server status, etc).
    This function uses text protocol to send a possible result set.

  @param thd                thread handle

  @return
    none: in case of success, OK (or result set) packet is sent to the
    client, otherwise an error is set in THD
*/

void mysql_sql_stmt_execute(THD *thd)
{
  LEX *lex= thd->lex;
  Prepared_statement *stmt;
  LEX_STRING *name= &lex->prepared_stmt_name;
  /* Query text for binary, general or slow log, if any of them is open */
  String expanded_query;
  DBUG_ENTER("mysql_sql_stmt_execute");
  DBUG_PRINT("info", ("EXECUTE: %.*s\n", (int) name->length, name->str));

  if (!(stmt= (Prepared_statement*) thd->stmt_map.find_by_name(name)))
  {
    my_error(ER_UNKNOWN_STMT_HANDLER, MYF(0),
             name->length, name->str, "EXECUTE");
    DBUG_VOID_RETURN;
  }

  if (stmt->param_count != lex->prepared_stmt_params.elements)
  {
    my_error(ER_WRONG_ARGUMENTS, MYF(0), "EXECUTE");
    DBUG_VOID_RETURN;
  }

  DBUG_PRINT("info",("stmt: 0x%lx", (long) stmt));

  (void) stmt->execute_loop(&expanded_query, FALSE, NULL, NULL);

  DBUG_VOID_RETURN;
}


/**
  COM_STMT_FETCH handler: fetches requested amount of rows from cursor.

  @param thd                Thread handle
  @param packet             Packet from client (with stmt_id & num_rows)
  @param packet_length      Length of packet
*/

void mysqld_stmt_fetch(THD *thd, char *packet, uint packet_length)
{
  /* assume there is always place for 8-16 bytes */
  ulong stmt_id= uint4korr(packet);
  ulong num_rows= uint4korr(packet+4);
  Prepared_statement *stmt;
  Statement stmt_backup;
  Server_side_cursor *cursor;
  DBUG_ENTER("mysqld_stmt_fetch");

  /* First of all clear possible warnings from the previous command */
  mysql_reset_thd_for_next_command(thd);
  status_var_increment(thd->status_var.com_stmt_fetch);
  if (!(stmt= find_prepared_statement(thd, stmt_id)))
  {
    char llbuf[22];
    my_error(ER_UNKNOWN_STMT_HANDLER, MYF(0), sizeof(llbuf),
             llstr(stmt_id, llbuf), "mysqld_stmt_fetch");
    DBUG_VOID_RETURN;
  }

  cursor= stmt->cursor;
  if (!cursor)
  {
    my_error(ER_STMT_HAS_NO_OPEN_CURSOR, MYF(0), stmt_id);
    DBUG_VOID_RETURN;
  }

  thd->stmt_arena= stmt;
  thd->set_n_backup_statement(stmt, &stmt_backup);

  if (!(specialflag & SPECIAL_NO_PRIOR))
    my_pthread_setprio(pthread_self(), QUERY_PRIOR);

  cursor->fetch(num_rows);

  if (!(specialflag & SPECIAL_NO_PRIOR))
    my_pthread_setprio(pthread_self(), WAIT_PRIOR);

  if (!cursor->is_open())
  {
    stmt->close_cursor();
    thd->cursor= 0;
    reset_stmt_params(stmt);
  }

  thd->restore_backup_statement(stmt, &stmt_backup);
  thd->stmt_arena= thd;

  DBUG_VOID_RETURN;
}


/**
  Reset a prepared statement in case there was a recoverable error.

    This function resets statement to the state it was right after prepare.
    It can be used to:
    - clear an error happened during mysqld_stmt_send_long_data
    - cancel long data stream for all placeholders without
      having to call mysqld_stmt_execute.
    - close an open cursor
    Sends 'OK' packet in case of success (statement was reset)
    or 'ERROR' packet (unrecoverable error/statement not found/etc).

  @param thd                Thread handle
  @param packet             Packet with stmt id
*/

void mysqld_stmt_reset(THD *thd, char *packet)
{
  /* There is always space for 4 bytes in buffer */
  ulong stmt_id= uint4korr(packet);
  Prepared_statement *stmt;
  DBUG_ENTER("mysqld_stmt_reset");

  /* First of all clear possible warnings from the previous command */
  mysql_reset_thd_for_next_command(thd);

  status_var_increment(thd->status_var.com_stmt_reset);
  if (!(stmt= find_prepared_statement(thd, stmt_id)))
  {
    char llbuf[22];
    my_error(ER_UNKNOWN_STMT_HANDLER, MYF(0), sizeof(llbuf),
             llstr(stmt_id, llbuf), "mysqld_stmt_reset");
    DBUG_VOID_RETURN;
  }

  stmt->close_cursor();

  /*
    Clear parameters from data which could be set by
    mysqld_stmt_send_long_data() call.
  */
  reset_stmt_params(stmt);

  stmt->state= Query_arena::PREPARED;

  general_log_print(thd, thd->command, NullS);

  my_ok(thd);

  DBUG_VOID_RETURN;
}


/**
  Delete a prepared statement from memory.

  @note
    we don't send any reply to this command.
*/

void mysqld_stmt_close(THD *thd, char *packet)
{
  /* There is always space for 4 bytes in packet buffer */
  ulong stmt_id= uint4korr(packet);
  Prepared_statement *stmt;
  DBUG_ENTER("mysqld_stmt_close");

  thd->stmt_da->disable_status();

  if (!(stmt= find_prepared_statement(thd, stmt_id)))
    DBUG_VOID_RETURN;

  /*
    The only way currently a statement can be deallocated when it's
    in use is from within Dynamic SQL.
  */
  DBUG_ASSERT(! stmt->is_in_use());
  stmt->deallocate();
  general_log_print(thd, thd->command, NullS);

  DBUG_VOID_RETURN;
}


/**
  SQLCOM_DEALLOCATE implementation.

    Close an SQL prepared statement. As this can be called from Dynamic
    SQL, we should be careful to not close a statement that is currently
    being executed.

  @return
    none: OK packet is sent in case of success, otherwise an error
    message is set in THD
*/

void mysql_sql_stmt_close(THD *thd)
{
  Prepared_statement* stmt;
  LEX_STRING *name= &thd->lex->prepared_stmt_name;
  DBUG_PRINT("info", ("DEALLOCATE PREPARE: %.*s\n", (int) name->length,
                      name->str));

  if (! (stmt= (Prepared_statement*) thd->stmt_map.find_by_name(name)))
    my_error(ER_UNKNOWN_STMT_HANDLER, MYF(0),
             name->length, name->str, "DEALLOCATE PREPARE");
  else if (stmt->is_in_use())
    my_error(ER_PS_NO_RECURSION, MYF(0));
  else
  {
    stmt->deallocate();
    my_ok(thd);
  }
}

/**
  Handle long data in pieces from client.

    Get a part of a long data. To make the protocol efficient, we are
    not sending any return packets here. If something goes wrong, then
    we will send the error on 'execute' We assume that the client takes
    care of checking that all parts are sent to the server. (No checking
    that we get a 'end of column' in the server is performed).

  @param thd                Thread handle
  @param packet             String to append
  @param packet_length      Length of string (including end \\0)
*/

void mysql_stmt_get_longdata(THD *thd, char *packet, ulong packet_length)
{
  ulong stmt_id;
  uint param_number;
  Prepared_statement *stmt;
  Item_param *param;
#ifndef EMBEDDED_LIBRARY
  char *packet_end= packet + packet_length;
#endif
  DBUG_ENTER("mysql_stmt_get_longdata");

  status_var_increment(thd->status_var.com_stmt_send_long_data);

  thd->stmt_da->disable_status();
#ifndef EMBEDDED_LIBRARY
  /* Minimal size of long data packet is 6 bytes */
  if (packet_length < MYSQL_LONG_DATA_HEADER)
    DBUG_VOID_RETURN;
#endif

  stmt_id= uint4korr(packet);
  packet+= 4;

  if (!(stmt=find_prepared_statement(thd, stmt_id)))
    DBUG_VOID_RETURN;

  param_number= uint2korr(packet);
  packet+= 2;
#ifndef EMBEDDED_LIBRARY
  if (param_number >= stmt->param_count)
  {
    /* Error will be sent in execute call */
    stmt->state= Query_arena::ERROR;
    stmt->last_errno= ER_WRONG_ARGUMENTS;
    sprintf(stmt->last_error, ER(ER_WRONG_ARGUMENTS),
            "mysqld_stmt_send_long_data");
    DBUG_VOID_RETURN;
  }
#endif

  param= stmt->param_array[param_number];

#ifndef EMBEDDED_LIBRARY
  if (param->set_longdata(packet, (ulong) (packet_end - packet)))
#else
  if (param->set_longdata(thd->extra_data, thd->extra_length))
#endif
  {
    stmt->state= Query_arena::ERROR;
    stmt->last_errno= ER_OUTOFMEMORY;
    sprintf(stmt->last_error, ER(ER_OUTOFMEMORY), 0);
  }

  general_log_print(thd, thd->command, NullS);

  DBUG_VOID_RETURN;
}


/***************************************************************************
 Select_fetch_protocol_binary
****************************************************************************/

Select_fetch_protocol_binary::Select_fetch_protocol_binary(THD *thd_arg)
  :protocol(thd_arg)
{}

bool Select_fetch_protocol_binary::send_fields(List<Item> &list, uint flags)
{
  bool rc;
  Protocol *save_protocol= thd->protocol;

  /*
    Protocol::send_fields caches the information about column types:
    this information is later used to send data. Therefore, the same
    dedicated Protocol object must be used for all operations with
    a cursor.
  */
  thd->protocol= &protocol;
  rc= select_send::send_fields(list, flags);
  thd->protocol= save_protocol;

  return rc;
}

bool Select_fetch_protocol_binary::send_eof()
{
  ::my_eof(thd);
  return FALSE;
}


bool
Select_fetch_protocol_binary::send_data(List<Item> &fields)
{
  Protocol *save_protocol= thd->protocol;
  bool rc;

  thd->protocol= &protocol;
  rc= select_send::send_data(fields);
  thd->protocol= save_protocol;
  return rc;
}

/*******************************************************************
* Reprepare_observer
*******************************************************************/
/** Push an error to the error stack and return TRUE for now. */

bool
Reprepare_observer::report_error(THD *thd)
{
  /*
    This 'error' is purely internal to the server:
    - No exception handler is invoked,
    - No condition is added in the condition area (warn_list).
    The diagnostics area is set to an error status to enforce
    that this thread execution stops and returns to the caller,
    backtracking all the way to Prepared_statement::execute_loop().
  */
  thd->stmt_da->set_error_status(thd, ER_NEED_REPREPARE,
                                 ER(ER_NEED_REPREPARE), "HY000");
  m_invalidated= TRUE;

  return TRUE;
}


/***************************************************************************
 Prepared_statement
****************************************************************************/

Prepared_statement::Prepared_statement(THD *thd_arg)
  :Statement(NULL, &main_mem_root,
             INITIALIZED, ++thd_arg->statement_id_counter),
  thd(thd_arg),
  result(thd_arg),
  param_array(0),
  param_count(0),
  last_errno(0),
  flags((uint) IS_IN_USE),
  m_sp_cache_version(0)
{
  init_sql_alloc(&main_mem_root, thd_arg->variables.query_alloc_block_size,
                  thd_arg->variables.query_prealloc_size);
  *last_error= '\0';
}


void Prepared_statement::setup_set_params()
{
  /*
    Note: BUG#25843 applies here too (query cache lookup uses thd->db, not
    db from "prepare" time).
  */
  if (query_cache_maybe_disabled(thd)) // we won't expand the query
    lex->safe_to_cache_query= FALSE;   // so don't cache it at Execution

  /*
    Decide if we have to expand the query (because we must write it to logs or
    because we want to look it up in the query cache) or not.
  */
  if ((mysql_bin_log.is_open() && is_update_query(lex->sql_command)) ||
      opt_log || opt_slow_log ||
      query_cache_is_cacheable_query(lex))
  {
    set_params_from_vars= insert_params_from_vars_with_log;
#ifndef EMBEDDED_LIBRARY
    set_params= insert_params_with_log;
#else
    set_params_data= emb_insert_params_with_log;
#endif
  }
  else
  {
    set_params_from_vars= insert_params_from_vars;
#ifndef EMBEDDED_LIBRARY
    set_params= insert_params;
#else
    set_params_data= emb_insert_params;
#endif
  }
}


/**
  Destroy this prepared statement, cleaning up all used memory
  and resources.

  This is called from ::deallocate() to handle COM_STMT_CLOSE and
  DEALLOCATE PREPARE or when THD ends and all prepared statements are freed.
*/

Prepared_statement::~Prepared_statement()
{
  DBUG_ENTER("Prepared_statement::~Prepared_statement");
  DBUG_PRINT("enter",("stmt: 0x%lx  cursor: 0x%lx",
                      (long) this, (long) cursor));
  delete cursor;
  /*
    We have to call free on the items even if cleanup is called as some items,
    like Item_param, don't free everything until free_items()
  */
  free_items();
  if (lex)
  {
    delete lex->result;
    delete (st_lex_local *) lex;
  }
  free_root(&main_mem_root, MYF(0));
  DBUG_VOID_RETURN;
}


Query_arena::Type Prepared_statement::type() const
{
  return PREPARED_STATEMENT;
}


void Prepared_statement::cleanup_stmt()
{
  DBUG_ENTER("Prepared_statement::cleanup_stmt");
  DBUG_PRINT("enter",("stmt: 0x%lx", (long) this));

  DBUG_ASSERT(lex->sphead == 0);
  /* The order is important */
  lex->unit.cleanup();
  cleanup_items(free_list);
  thd->cleanup_after_query();
  close_thread_tables(thd);
  thd->rollback_item_tree_changes();

  DBUG_VOID_RETURN;
}


bool Prepared_statement::set_name(LEX_STRING *name_arg)
{
  name.length= name_arg->length;
  name.str= (char*) memdup_root(mem_root, name_arg->str, name_arg->length);
  return name.str == 0;
}


/**
  Remember the current database.

  We must reset/restore the current database during execution of
  a prepared statement since it affects execution environment:
  privileges, @@character_set_database, and other.

  @return Returns an error if out of memory.
*/

bool
Prepared_statement::set_db(const char *db_arg, uint db_length_arg)
{
  /* Remember the current database. */
  if (db_arg && db_length_arg)
  {
    db= this->strmake(db_arg, db_length_arg);
    db_length= db_length_arg;
  }
  else
  {
    db= NULL;
    db_length= 0;
  }
  return db_arg != NULL && db == NULL;
}

/**************************************************************************
  Common parts of mysql_[sql]_stmt_prepare, mysql_[sql]_stmt_execute.
  Essentially, these functions do all the magic of preparing/executing
  a statement, leaving network communication, input data handling and
  global THD state management to the caller.
***************************************************************************/

/**
  Parse statement text, validate the statement, and prepare it for execution.

    You should not change global THD state in this function, if at all
    possible: it may be called from any context, e.g. when executing
    a COM_* command, and SQLCOM_* command, or a stored procedure.

  @param packet             statement text
  @param packet_len

  @note
    Precondition:
    The caller must ensure that thd->change_list and thd->free_list
    is empty: this function will not back them up but will free
    in the end of its execution.

  @note
    Postcondition:
    thd->mem_root contains unused memory allocated during validation.
*/

bool Prepared_statement::prepare(const char *packet, uint packet_len)
{
  bool error;
  Statement stmt_backup;
  Query_arena *old_stmt_arena;
  DBUG_ENTER("Prepared_statement::prepare");
  /*
    If this is an SQLCOM_PREPARE, we also increase Com_prepare_sql.
    However, it seems handy if com_stmt_prepare is increased always,
    no matter what kind of prepare is processed.
  */
  status_var_increment(thd->status_var.com_stmt_prepare);

  if (! (lex= new (mem_root) st_lex_local))
    DBUG_RETURN(TRUE);

  if (set_db(thd->db, thd->db_length))
    DBUG_RETURN(TRUE);

  /*
    alloc_query() uses thd->memroot && thd->query, so we should call
    both of backup_statement() and backup_query_arena() here.
  */
  thd->set_n_backup_statement(this, &stmt_backup);
  thd->set_n_backup_active_arena(this, &stmt_backup);

  if (alloc_query(thd, packet, packet_len))
  {
    thd->restore_backup_statement(this, &stmt_backup);
    thd->restore_active_arena(this, &stmt_backup);
    DBUG_RETURN(TRUE);
  }

  old_stmt_arena= thd->stmt_arena;
  thd->stmt_arena= this;

  Parser_state parser_state(thd, thd->query, thd->query_length);
  parser_state.m_lip.stmt_prepare_mode= TRUE;
  lex_start(thd);

  error= parse_sql(thd, & parser_state, NULL) ||
         thd->is_error() ||
         init_param_array(this);

  lex->set_trg_event_type_for_tables();

  /*
    While doing context analysis of the query (in check_prepared_statement)
    we allocate a lot of additional memory: for open tables, JOINs, derived
    tables, etc.  Let's save a snapshot of current parse tree to the
    statement and restore original THD. In cases when some tree
    transformation can be reused on execute, we set again thd->mem_root from
    stmt->mem_root (see setup_wild for one place where we do that).
  */
  thd->restore_active_arena(this, &stmt_backup);

  /*
    If called from a stored procedure, ensure that we won't rollback
    external changes when cleaning up after validation.
  */
  DBUG_ASSERT(thd->change_list.is_empty());

  /* 
   The only case where we should have items in the thd->free_list is
   after stmt->set_params_from_vars(), which may in some cases create
   Item_null objects.
  */

  if (error == 0)
    error= check_prepared_statement(this);

  /*
    Currently CREATE PROCEDURE/TRIGGER/EVENT are prohibited in prepared
    statements: ensure we have no memory leak here if by someone tries
    to PREPARE stmt FROM "CREATE PROCEDURE ..."
  */
  DBUG_ASSERT(lex->sphead == NULL || error != 0);
  if (lex->sphead)
  {
    delete lex->sphead;
    lex->sphead= NULL;
  }

  lex_end(lex);
  cleanup_stmt();
  thd->restore_backup_statement(this, &stmt_backup);
  thd->stmt_arena= old_stmt_arena;

  if (error == 0)
  {
    setup_set_params();
    init_stmt_after_parse(lex);
    state= Query_arena::PREPARED;
    flags&= ~ (uint) IS_IN_USE;
    /*
      This is for prepared statement validation purposes.
      A statement looks up and pre-loads all its stored functions
      at prepare. Later on, if a function is gone from the cache,
      execute may fail.
      Remember the cache version to be able to invalidate the prepared
      statement at execute if it changes.
      We only need to care about version of the stored functions cache:
      if a prepared statement uses a stored procedure, it's indirect,
      via a stored function. The only exception is SQLCOM_CALL,
      but the latter one looks up the stored procedure each time
      it's invoked, rather than once at prepare.
    */
    m_sp_cache_version= sp_cache_version(&thd->sp_func_cache);

    /* 
      Log COM_EXECUTE to the general log. Note, that in case of SQL
      prepared statements this causes two records to be output:

      Query       PREPARE stmt from @user_variable
      Prepare     <statement SQL text>

      This is considered user-friendly, since in the
      second log entry we output the actual statement text.

      Do not print anything if this is an SQL prepared statement and
      we're inside a stored procedure (also called Dynamic SQL) --
      sub-statements inside stored procedures are not logged into
      the general log.
    */
    if (thd->spcont == NULL)
      general_log_write(thd, COM_STMT_PREPARE, query, query_length);
  }
  DBUG_RETURN(error);
}


/**
  Assign parameter values either from variables, in case of SQL PS
  or from the execute packet.

  @param expanded_query  a container with the original SQL statement.
                         '?' placeholders will be replaced with
                         their values in case of success.
                         The result is used for logging and replication
  @param packet          pointer to execute packet.
                         NULL in case of SQL PS
  @param packet_end      end of the packet. NULL in case of SQL PS

  @todo Use a paremeter source class family instead of 'if's, and
  support stored procedure variables.

  @retval TRUE an error occurred when assigning a parameter (likely
          a conversion error or out of memory, or malformed packet)
  @retval FALSE success
*/

bool
Prepared_statement::set_parameters(String *expanded_query,
                                   uchar *packet, uchar *packet_end)
{
  bool is_sql_ps= packet == NULL;
  bool res= FALSE;

  if (is_sql_ps)
  {
    /* SQL prepared statement */
    res= set_params_from_vars(this, thd->lex->prepared_stmt_params,
                              expanded_query);
  }
  else if (param_count)
  {
#ifndef EMBEDDED_LIBRARY
    uchar *null_array= packet;
    res= (setup_conversion_functions(this, &packet, packet_end) ||
          set_params(this, null_array, packet, packet_end, expanded_query));
#else
    /*
      In embedded library we re-install conversion routines each time
      we set parameters, and also we don't need to parse packet.
      So we do it in one function.
    */
    res= set_params_data(this, expanded_query);
#endif
  }
  if (res)
  {
    my_error(ER_WRONG_ARGUMENTS, MYF(0),
             is_sql_ps ? "EXECUTE" : "mysqld_stmt_execute");
    reset_stmt_params(this);
  }
  return res;
}


/**
  Execute a prepared statement. Re-prepare it a limited number
  of times if necessary.

  Try to execute a prepared statement. If there is a metadata
  validation error, prepare a new copy of the prepared statement,
  swap the old and the new statements, and try again.
  If there is a validation error again, repeat the above, but
  perform no more than MAX_REPREPARE_ATTEMPTS.

  @note We have to try several times in a loop since we
  release metadata locks on tables after prepared statement
  prepare. Therefore, a DDL statement may sneak in between prepare
  and execute of a new statement. If this happens repeatedly
  more than MAX_REPREPARE_ATTEMPTS times, we give up.

  In future we need to be able to keep the metadata locks between
  prepare and execute, but right now open_and_lock_tables(), as
  well as close_thread_tables() are buried deep inside
  execution code (mysql_execute_command()).

  @return TRUE if an error, FALSE if success
  @retval  TRUE    either MAX_REPREPARE_ATTEMPTS has been reached,
                   or some general error
  @retval  FALSE   successfully executed the statement, perhaps
                   after having reprepared it a few times.
*/

bool
Prepared_statement::execute_loop(String *expanded_query,
                                 bool open_cursor,
                                 uchar *packet,
                                 uchar *packet_end)
{
  const int MAX_REPREPARE_ATTEMPTS= 3;
  Reprepare_observer reprepare_observer;
  bool error;
  int reprepare_attempt= 0;

  if (set_parameters(expanded_query, packet, packet_end))
    return TRUE;

reexecute:
  reprepare_observer.reset_reprepare_observer();

  /*
    If the free_list is not empty, we'll wrongly free some externally
    allocated items when cleaning up after validation of the prepared
    statement.
  */
  DBUG_ASSERT(thd->free_list == NULL);

  /*
    Install the metadata observer. If some metadata version is
    different from prepare time and an observer is installed,
    the observer method will be invoked to push an error into
    the error stack.
  */
  if (sql_command_flags[lex->sql_command] &
      CF_REEXECUTION_FRAGILE)
  {
    DBUG_ASSERT(thd->m_reprepare_observer == NULL);
    thd->m_reprepare_observer = &reprepare_observer;
  }

  if (!(specialflag & SPECIAL_NO_PRIOR))
    my_pthread_setprio(pthread_self(),QUERY_PRIOR);

  error= execute(expanded_query, open_cursor) || thd->is_error();

  if (!(specialflag & SPECIAL_NO_PRIOR))
    my_pthread_setprio(pthread_self(), WAIT_PRIOR);

  thd->m_reprepare_observer= NULL;

  if (error && !thd->is_fatal_error && !thd->killed &&
      reprepare_observer.is_invalidated() &&
      reprepare_attempt++ < MAX_REPREPARE_ATTEMPTS)
  {
    DBUG_ASSERT(thd->stmt_da->sql_errno() == ER_NEED_REPREPARE);
    thd->clear_error();

    error= reprepare();

    if (! error)                                /* Success */
      goto reexecute;
  }
  reset_stmt_params(this);

  return error;
}


/**
  Reprepare this prepared statement.

  Currently this is implemented by creating a new prepared
  statement, preparing it with the original query and then
  swapping the new statement and the original one.

  @retval  TRUE   an error occurred. Possible errors include
                  incompatibility of new and old result set
                  metadata
  @retval  FALSE  success, the statement has been reprepared
*/

bool
Prepared_statement::reprepare()
{
  char saved_cur_db_name_buf[NAME_LEN+1];
  LEX_STRING saved_cur_db_name=
    { saved_cur_db_name_buf, sizeof(saved_cur_db_name_buf) };
  LEX_STRING stmt_db_name= { db, db_length };
  bool cur_db_changed;
  bool error;

  Prepared_statement copy(thd);

  copy.set_sql_prepare(); /* To suppress sending metadata to the client. */

  status_var_increment(thd->status_var.com_stmt_reprepare);

  if (mysql_opt_change_db(thd, &stmt_db_name, &saved_cur_db_name, TRUE,
                          &cur_db_changed))
    return TRUE;

  error= ((name.str && copy.set_name(&name)) ||
          copy.prepare(query, query_length) ||
          validate_metadata(&copy));

  if (cur_db_changed)
    mysql_change_db(thd, &saved_cur_db_name, TRUE);

  if (! error)
  {
    swap_prepared_statement(&copy);
    swap_parameter_array(param_array, copy.param_array, param_count);
#ifndef DBUG_OFF
    is_reprepared= TRUE;
#endif
    /*
      Clear possible warnings during reprepare, it has to be completely
      transparent to the user. We use clear_warning_info() since
      there were no separate query id issued for re-prepare.
      Sic: we can't simply silence warnings during reprepare, because if
      it's failed, we need to return all the warnings to the user.
    */
    thd->warning_info->clear_warning_info(thd->query_id);
  }
  return error;
}


/**
  Validate statement result set metadata (if the statement returns
  a result set).

  Currently we only check that the number of columns of the result
  set did not change.
  This is a helper method used during re-prepare.

  @param[in]  copy  the re-prepared prepared statement to verify
                    the metadata of

  @retval TRUE  error, ER_PS_REBIND is reported
  @retval FALSE statement return no or compatible metadata
*/


bool Prepared_statement::validate_metadata(Prepared_statement *copy)
{
  /**
    If this is an SQL prepared statement or EXPLAIN,
    return FALSE -- the metadata of the original SELECT,
    if any, has not been sent to the client.
  */
  if (is_sql_prepare() || lex->describe)
    return FALSE;

  if (lex->select_lex.item_list.elements !=
      copy->lex->select_lex.item_list.elements)
  {
    /** Column counts mismatch, update the client */
    thd->server_status|= SERVER_STATUS_METADATA_CHANGED;
  }

  return FALSE;
}


/**
  Replace the original prepared statement with a prepared copy.

  This is a private helper that is used as part of statement
  reprepare

  @return This function does not return any errors.
*/

void
Prepared_statement::swap_prepared_statement(Prepared_statement *copy)
{
  Statement tmp_stmt;

  /* Swap memory roots. */
  swap_variables(MEM_ROOT, main_mem_root, copy->main_mem_root);

  /* Swap the arenas */
  tmp_stmt.set_query_arena(this);
  set_query_arena(copy);
  copy->set_query_arena(&tmp_stmt);

  /* Swap the statement parent classes */
  tmp_stmt.set_statement(this);
  set_statement(copy);
  copy->set_statement(&tmp_stmt);

  /* Swap ids back, we need the original id */
  swap_variables(ulong, id, copy->id);
  /* Swap mem_roots back, they must continue pointing at the main_mem_roots */
  swap_variables(MEM_ROOT *, mem_root, copy->mem_root);
  /*
    Swap the old and the new parameters array. The old array
    is allocated in the old arena.
  */
  swap_variables(Item_param **, param_array, copy->param_array);
  /* Swap flags: this is perhaps unnecessary */
  swap_variables(uint, flags, copy->flags);
  /* Swap names, the old name is allocated in the wrong memory root */
  swap_variables(LEX_STRING, name, copy->name);
  /* Ditto */
  swap_variables(char *, db, copy->db);
  swap_variables(ulong, m_sp_cache_version, copy->m_sp_cache_version);

  DBUG_ASSERT(db_length == copy->db_length);
  DBUG_ASSERT(param_count == copy->param_count);
  DBUG_ASSERT(thd == copy->thd);
  last_error[0]= '\0';
  last_errno= 0;
}


/**
  Execute a prepared statement.

    You should not change global THD state in this function, if at all
    possible: it may be called from any context, e.g. when executing
    a COM_* command, and SQLCOM_* command, or a stored procedure.

  @param expanded_query     A query for binlogging which has all parameter
                            markers ('?') replaced with their actual values.
  @param open_cursor        True if an attempt to open a cursor should be made.
                            Currenlty used only in the binary protocol.

  @note
    Preconditions, postconditions.
    - See the comment for Prepared_statement::prepare().

  @retval
    FALSE	    ok
  @retval
    TRUE		Error
*/

bool Prepared_statement::execute(String *expanded_query, bool open_cursor)
{
  Statement stmt_backup;
  Query_arena *old_stmt_arena;
  bool error= TRUE;

  char saved_cur_db_name_buf[NAME_LEN+1];
  LEX_STRING saved_cur_db_name=
    { saved_cur_db_name_buf, sizeof(saved_cur_db_name_buf) };
  bool cur_db_changed;

  LEX_STRING stmt_db_name= { db, db_length };

  status_var_increment(thd->status_var.com_stmt_execute);

  /* Check if we got an error when sending long data */
  if (state == Query_arena::ERROR)
  {
    my_message(last_errno, last_error, MYF(0));
    return TRUE;
  }
  if (flags & (uint) IS_IN_USE)
  {
    my_error(ER_PS_NO_RECURSION, MYF(0));
    return TRUE;
  }

  /*
    Reprepare the statement if we're using stored functions
    and the version of the stored routines cache has changed.
  */
  if (lex->uses_stored_routines() &&
      m_sp_cache_version != sp_cache_version(&thd->sp_func_cache) &&
      thd->m_reprepare_observer &&
      thd->m_reprepare_observer->report_error(thd))
  {
    return TRUE;
  }


  /*
    For SHOW VARIABLES lex->result is NULL, as it's a non-SELECT
    command. For such queries we don't return an error and don't
    open a cursor -- the client library will recognize this case and
    materialize the result set.
    For SELECT statements lex->result is created in
    check_prepared_statement. lex->result->simple_select() is FALSE
    in INSERT ... SELECT and similar commands.
  */

  if (open_cursor && lex->result && lex->result->check_simple_select())
  {
    DBUG_PRINT("info",("Cursor asked for not SELECT stmt"));
    return TRUE;
  }

  /* In case the command has a call to SP which re-uses this statement name */
  flags|= IS_IN_USE;

  close_cursor();

  /*
    If the free_list is not empty, we'll wrongly free some externally
    allocated items when cleaning up after execution of this statement.
  */
  DBUG_ASSERT(thd->change_list.is_empty());

  /* 
   The only case where we should have items in the thd->free_list is
   after stmt->set_params_from_vars(), which may in some cases create
   Item_null objects.
  */

  thd->set_n_backup_statement(this, &stmt_backup);

  /*
    Change the current database (if needed).

    Force switching, because the database of the prepared statement may be
    NULL (prepared statements can be created while no current database
    selected).
  */

  if (mysql_opt_change_db(thd, &stmt_db_name, &saved_cur_db_name, TRUE,
                          &cur_db_changed))
    goto error;

  /* Allocate query. */

  if (expanded_query->length() &&
      alloc_query(thd, (char*) expanded_query->ptr(),
                  expanded_query->length()))
  {
    my_error(ER_OUTOFMEMORY, 0, expanded_query->length());
    goto error;
  }
  /*
    Expanded query is needed for slow logging, so we want thd->query
    to point at it even after we restore from backup. This is ok, as
    expanded query was allocated in thd->mem_root.
  */
  stmt_backup.query= thd->query;
  stmt_backup.query_length= thd->query_length;

  /*
    At first execution of prepared statement we may perform logical
    transformations of the query tree. Such changes should be performed
    on the parse tree of current prepared statement and new items should
    be allocated in its memory root. Set the appropriate pointer in THD
    to the arena of the statement.
  */
  old_stmt_arena= thd->stmt_arena;
  thd->stmt_arena= this;
  reinit_stmt_before_use(thd, lex);

  /* Go! */

  if (open_cursor)
    error= mysql_open_cursor(thd, (uint) ALWAYS_MATERIALIZED_CURSOR,
                             &result, &cursor);
  else
  {
    /*
      Try to find it in the query cache, if not, execute it.
      Note that multi-statements cannot exist here (they are not supported in
      prepared statements).
    */
    if (query_cache_send_result_to_client(thd, thd->query,
                                          thd->query_length) <= 0)
    {
      MYSQL_QUERY_EXEC_START(thd->query,
                             thd->thread_id,
                             (char *) (thd->db ? thd->db : ""),
                             thd->security_ctx->priv_user,
                             (char *) thd->security_ctx->host_or_ip,
                             1);
      error= mysql_execute_command(thd);
      MYSQL_QUERY_EXEC_DONE(error);
    }
  }

  /*
    Restore the current database (if changed).

    Force switching back to the saved current database (if changed),
    because it may be NULL. In this case, mysql_change_db() would generate
    an error.
  */

  if (cur_db_changed)
    mysql_change_db(thd, &saved_cur_db_name, TRUE);

  /* Assert that if an error, no cursor is open */
  DBUG_ASSERT(! (error && cursor));

  if (! cursor)
    cleanup_stmt();

  thd->set_statement(&stmt_backup);
  thd->stmt_arena= old_stmt_arena;

  if (state == Query_arena::PREPARED)
    state= Query_arena::EXECUTED;

  /*
    Log COM_EXECUTE to the general log. Note, that in case of SQL
    prepared statements this causes two records to be output:

    Query       EXECUTE <statement name>
    Execute     <statement SQL text>

    This is considered user-friendly, since in the
    second log entry we output values of parameter markers.

    Do not print anything if this is an SQL prepared statement and
    we're inside a stored procedure (also called Dynamic SQL) --
    sub-statements inside stored procedures are not logged into
    the general log.
  */
  if (error == 0 && thd->spcont == NULL)
    general_log_write(thd, COM_STMT_EXECUTE, thd->query, thd->query_length);

error:
  flags&= ~ (uint) IS_IN_USE;
  return error;
}


/** Common part of DEALLOCATE PREPARE and mysqld_stmt_close. */

void Prepared_statement::deallocate()
{
  /* We account deallocate in the same manner as mysqld_stmt_close */
  status_var_increment(thd->status_var.com_stmt_close);
  /* Statement map calls delete stmt on erase */
  thd->stmt_map.erase(this);
}