SHOW STATUS does not anymore change local status variables (except...

SHOW STATUS does not anymore change local status variables (except com_show_status). Global status variables are still updated.
SHOW STATUS are not anymore put in slow query log because of no index usage.

Implemntation done by removing orig_sql_command and moving logic of SHOW STATUS to mysql_excute_command()
This simplifies code and allows us to remove some if statements all over the code.

Upgraded uc_update_queries[] to sql_command_flags and added more bitmaps to better categorize commands.
This allowed some overall simplifaction when testing sql_command.

Fixes bugs:
Bug#10210: running SHOW STATUS increments counters it shouldn't
Bug#19764: SHOW commands end up in the slow log as table scans


mysql-test/r/grant_cache.result:
  Fixed results after SHOW STATUS doesn't anymore affect status variables
mysql-test/r/information_schema.result:
  Added extra test to cover more code
mysql-test/r/query_cache.result:
  Remove resuts from previous tests
mysql-test/r/status.result:
  Added more tests for testing of last_query_cost and how SHOW STATUS affects status variables.
  (Bug#10210)
mysql-test/r/temp_table.result:
  Fixed results after SHOW STATUS doesn't anymore affect status variables
mysql-test/r/union.result:
  Fixed results after SHOW STATUS is not logged to slow query log
  (Bug#19764)
mysql-test/t/events_microsec.test:
  Disable warnings at init
mysql-test/t/information_schema.test:
  Added extra test to cover more code
mysql-test/t/query_cache.test:
  Remove resuts from previous tests
mysql-test/t/status.test:
  Added more tests for testing of last_query_cost and how SHOW STATUS affects status variables.
  (Bug #10210)
sql/mysql_priv.h:
  Added 'sql_command_flags'
sql/sql_class.cc:
  New function add_diff_to_status(), used to update global status variables when using SHOW STATUS
sql/sql_class.h:
  New function 'fill_information_schema_tables()'
  (One could not anymore use fill_derived_tables() for this as only_view_structures() is not relevant for information schema tables)
  Added defines for bit flags in sql_command_flags[]
sql/sql_lex.cc:
  Remove orig_sql_command
sql/sql_lex.h:
  Remove orig_sql_command
sql/sql_parse.cc:
  Rename uc_update_queries -> sql_command_flags.
  Enhanced 'sql_command_flags' to better classify SQL commands
  uc_update_queries[] != 0 is changed to (sql_command_flags[] & CF_CHANGES_DATA)
  lex->orig_sql_command == SQLCOM_END is changed to (sql_command_flags[lex->sql_command] & CF_STATUS_COMMAND) == 0)
  
  Simplify incrementing of thd->status_var.com_stat[] as we don't have to do special handling for SHOW commands.
  
  Split SQLCOM_SELECT handling in mysql_execute_command() to a separate function.
  Added special handling of SHOW STATUS commands in mysql_execute_command() and call common SQLCOM_SELECT handling.
  These changes allows us to easily fix that we save and restore status variables during execution of a SHOW STATUS command.
  Don't log SHOW STATUS commands to slow query log.
  
  This fixes Bug#10210 and Bug#19764 without adding additional 'if' code.
  (The new code is faster than the original as we now have fewer if's than before)
sql/sql_prepare.cc:
  Clean up prepare-check handling of SQLCOM commands by using sql_command_flags[]
  This simplifes code and ensures that code works even if someone forgets to put a new status commands into the switch statement.
sql/sql_select.cc:
  Remove special handling of SHOW STATUS.
  (This is now done in SQLCOM_SHOW_STATUS part in mysql_execute_command())
sql/sql_show.cc:
  Remove orig_sql_command
  Only change sql_command during 'open_normal_and_derived_tables()' (for views) and not for the full duration of generating data.
  Changed 'show status' to use thd->initial_status_var to ensure that the current statement is not affecting the to-be-used values.
  Use thd->fill_information_schema_tables() instead of 'thd->fill_derived_tables()' as the later wrongly checks the value of sql_command.
sql/sql_yacc.yy:
  Remove usage of orig_sql_command.
  One side effect of this is that we need to test for cursors if the current command is a SELECT or a SHOW command.
sql/structs.h:
  Updated comment

mysql-test/r/grant_cache.result

@@ -60,7 +60,7 @@ Variable_name	Value
 Qcache_hits	0
 show status like "Qcache_not_cached";
 Variable_name	Value
-Qcache_not_cached	5
+Qcache_not_cached	0
 select "user1";
 user1
 user1
@@ -72,7 +72,7 @@ Variable_name	Value
 Qcache_hits	0
 show status like "Qcache_not_cached";
 Variable_name	Value
-Qcache_not_cached	9
+Qcache_not_cached	1
 select * from t1;
 a	b	c
 1	1	1
@@ -85,7 +85,7 @@ Variable_name	Value
 Qcache_hits	1
 show status like "Qcache_not_cached";
 Variable_name	Value
-Qcache_not_cached	12
+Qcache_not_cached	1
 select a from t1 ;
 a
 1
@@ -98,7 +98,7 @@ Variable_name	Value
 Qcache_hits	2
 show status like "Qcache_not_cached";
 Variable_name	Value
-Qcache_not_cached	15
+Qcache_not_cached	1
 select c from t1;
 c
 1
@@ -111,7 +111,7 @@ Variable_name	Value
 Qcache_hits	3
 show status like "Qcache_not_cached";
 Variable_name	Value
-Qcache_not_cached	18
+Qcache_not_cached	1
 show grants for current_user();
 Grants for @localhost
 GRANT USAGE ON *.* TO ''@'localhost'
@@ -144,7 +144,7 @@ Variable_name	Value
 Qcache_hits	7
 show status like "Qcache_not_cached";
 Variable_name	Value
-Qcache_not_cached	22
+Qcache_not_cached	2
 select "user3";
 user3
 user3
@@ -168,7 +168,7 @@ Variable_name	Value
 Qcache_hits	7
 show status like "Qcache_not_cached";
 Variable_name	Value
-Qcache_not_cached	30
+Qcache_not_cached	7
 select "user4";
 user4
 user4
@@ -198,7 +198,7 @@ Variable_name	Value
 Qcache_hits	8
 show status like "Qcache_not_cached";
 Variable_name	Value
-Qcache_not_cached	34
+Qcache_not_cached	8
 set names binary;
 delete from mysql.user where user in ("mysqltest_1","mysqltest_2","mysqltest_3");
 delete from mysql.db where user in ("mysqltest_1","mysqltest_2","mysqltest_3");

mysql-test/r/information_schema.result

@@ -199,6 +199,8 @@ select table_name, column_name, privileges from information_schema.columns
 where table_schema = 'mysqltest' and table_name = 'v1';
 table_name	column_name	privileges
 v1	c	select
+explain select * from v1;
+ERROR HY000: EXPLAIN/SHOW can not be issued; lacking privileges for underlying table
 drop view v1, mysqltest.v1;
 drop tables mysqltest.t4, mysqltest.t1, t2, t3, t5;
 drop database mysqltest;

mysql-test/r/query_cache.result

@@ -1050,6 +1050,7 @@ Qcache_hits	1
 drop table t1;
 create table t1 (a int);
 insert into t1 values (1),(2);
+drop procedure if exists p1;
 CREATE PROCEDURE `p1`()
 begin
 Declare c1 cursor for select a from t1;

mysql-test/r/status.result

@@ -23,6 +23,32 @@ select 1;
 show status like 'last_query_cost';
 Variable_name	Value
 Last_query_cost	0.000000
+create table t1 (a int);
+insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
+insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
+insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
+insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
+insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
+select * from t1 where a=6;
+a
+6
+6
+6
+6
+6
+show status like 'last_query_cost';
+Variable_name	Value
+Last_query_cost	12.084449
+show status like 'last_query_cost';
+Variable_name	Value
+Last_query_cost	12.084449
+select 1;
+1
+1
+show status like 'last_query_cost';
+Variable_name	Value
+Last_query_cost	0.000000
+drop table t1;
 FLUSH STATUS;
 SHOW STATUS LIKE 'max_used_connections';
 Variable_name	Value
@@ -43,3 +69,27 @@ SHOW STATUS LIKE 'max_used_connections';
 Variable_name	Value
 Max_used_connections	5
 SET GLOBAL thread_cache_size=@save_thread_cache_size;
+show status like 'com_show_status';
+Variable_name	Value
+Com_show_status	3
+show status like 'hand%write%';
+Variable_name	Value
+Handler_write	0
+show status like '%tmp%';
+Variable_name	Value
+Created_tmp_disk_tables	0
+Created_tmp_files	0
+Created_tmp_tables	0
+show status like 'hand%write%';
+Variable_name	Value
+Handler_write	0
+show status like '%tmp%';
+Variable_name	Value
+Created_tmp_disk_tables	0
+Created_tmp_files	0
+Created_tmp_tables	0
+show status like 'com_show_status';
+Variable_name	Value
+Com_show_status	8
+rnd_diff	tmp_table_diff
+20	8

mysql-test/r/temp_table.result

@@ -98,7 +98,7 @@ d
 show status like "created_tmp%tables";
 Variable_name	Value
 Created_tmp_disk_tables	0
-Created_tmp_tables	2
+Created_tmp_tables	1
 drop table t1;
 create temporary table v1 as select 'This is temp. table' A;
 create view v1 as select 'This is view' A;

mysql-test/r/union.result

@@ -836,27 +836,27 @@ count(*)
 26
 show status like 'Slow_queries';
 Variable_name	Value
-Slow_queries	1
+Slow_queries	0
 select count(*) from t1 where b=13;
 count(*)
 10
 show status like 'Slow_queries';
 Variable_name	Value
-Slow_queries	3
+Slow_queries	1
 select count(*) from t1 where b=13 union select count(*) from t1 where a=7;
 count(*)
 10
 26
 show status like 'Slow_queries';
 Variable_name	Value
-Slow_queries	5
+Slow_queries	2
 select count(*) from t1 where a=7 union select count(*) from t1 where b=13;
 count(*)
 26
 10
 show status like 'Slow_queries';
 Variable_name	Value
-Slow_queries	7
+Slow_queries	3
 flush status;
 select a from t1 where b not in (1,2,3) union select a from t1 where b not in (4,5,6);
 a

mysql-test/t/events_microsec.test

+--disable_warnings
 create database if not exists events_test;
+--enable_warnings
+
 use events_test;
 
 --error ER_NOT_SUPPORTED_YET

mysql-test/t/information_schema.test

@@ -80,6 +80,8 @@ connect (user4,localhost,mysqltest_3,,mysqltest);
 connection user4;
 select table_name, column_name, privileges from information_schema.columns
 where table_schema = 'mysqltest' and table_name = 'v1';
+--error 1345
+explain select * from v1;
 connection default;
 
 drop view v1, mysqltest.v1;

mysql-test/t/query_cache.test

@@ -765,6 +765,9 @@ drop table t1;
 create table t1 (a int);
 insert into t1 values (1),(2);
 
+--disable_warnings
+drop procedure if exists p1;
+--enable_warnings
 delimiter //;
 CREATE PROCEDURE `p1`()
 begin

mysql-test/t/status.test

@@ -48,6 +48,19 @@ connection default;
 
 select 1;
 show status like 'last_query_cost';
+create table t1 (a int);
+insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
+insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
+insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
+insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
+insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
+select * from t1 where a=6;
+show status like 'last_query_cost';
+# Ensure value dosn't change by second status call
+show status like 'last_query_cost';
+select 1;
+show status like 'last_query_cost';
+drop table t1;
 
 #
 # Test for Bug #15933 max_used_connections is wrong after FLUSH STATUS
@@ -144,3 +157,24 @@ disconnect con2;
 disconnect con1;
 
 # End of 5.0 tests
+
+#
+# Ensure that SHOW STATUS only changes global status variables
+#
+
+connect (con1,localhost,root,,);
+let $rnd_next = `show global status like 'handler_read_rnd_next'`;
+let $tmp_table = `show global status like 'Created_tmp_tables'`;
+show status like 'com_show_status';
+show status like 'hand%write%';
+show status like '%tmp%';
+show status like 'hand%write%';
+show status like '%tmp%';
+show status like 'com_show_status';
+let $rnd_next2 = `show global status like 'handler_read_rnd_next'`;
+let $tmp_table2 = `show global status like 'Created_tmp_tables'`;
+--disable_query_log
+eval select substring_index('$rnd_next2',0x9,-1)-substring_index('$rnd_next',0x9,-1) as rnd_diff, substring_index('$tmp_table2',0x9,-1)-substring_index('$tmp_table',0x9,-1) as tmp_table_diff;
+--enable_query_log
+
+# End of 5.1 tests

sql/mysql_priv.h

@@ -1582,6 +1582,7 @@ extern TABLE *unused_tables;
 extern const char* any_db;
 extern struct my_option my_long_options[];
 extern const LEX_STRING view_type;
+extern uint sql_command_flags[];
 
 /* optional things, have_* variables */
 

sql/sql_class.cc

@@ -516,6 +516,31 @@ void add_to_status(STATUS_VAR *to_var, STATUS_VAR *from_var)
   /* it doesn't make sense to add last_query_cost values */
 }
 
+/*
+  Add the difference between two status variable arrays to another one.
+
+  SYNOPSIS
+    add_diff_to_status
+    to_var       add to this array
+    from_var     from this array
+    dec_var      minus this array
+  
+  NOTE
+    This function assumes that all variables are long/ulong.
+*/
+
+void add_diff_to_status(STATUS_VAR *to_var, STATUS_VAR *from_var,
+                        STATUS_VAR *dec_var)
+{
+  ulong *end= (ulong*) ((byte*) to_var + offsetof(STATUS_VAR,
+						  last_system_status_var) +
+			sizeof(ulong));
+  ulong *to= (ulong*) to_var, *from= (ulong*) from_var, *dec= (ulong*) dec_var;
+
+  while (to != end)
+    *(to++)+= *(from++) - *(dec++);
+}
+
 
 void THD::awake(THD::killed_state state_to_set)
 {

sql/sql_class.h

@@ -343,7 +343,6 @@ typedef struct system_status_var
 
 #define last_system_status_var com_stmt_close
 
-
 #ifdef MYSQL_SERVER
 
 void free_tmp_table(THD *thd, TABLE *entry);
@@ -833,6 +832,7 @@ class THD :public Statement,
   struct  rand_struct rand;		// used for authentication
   struct  system_variables variables;	// Changeable local variables
   struct  system_status_var status_var; // Per thread statistic vars
+  struct  system_status_var *initial_status_var; /* used by show status */
   THR_LOCK_INFO lock_info;              // Locking info of this thread
   THR_LOCK_OWNER main_lock_id;          // To use for conventional queries
   THR_LOCK_OWNER *lock_id;              // If not main_lock_id, points to
@@ -1306,6 +1306,10 @@ class THD :public Statement,
   {
     return !stmt_arena->is_stmt_prepare() && !lex->only_view_structure();
   }
+  inline bool fill_information_schema_tables()
+  {
+    return !stmt_arena->is_stmt_prepare();
+  }
   inline gptr trans_alloc(unsigned int size)
   {
     return alloc_root(&transaction.mem_root,size);
@@ -1952,8 +1956,16 @@ class select_dumpvar :public select_result_interceptor {
   void cleanup();
 };
 
+/* Bits in sql_command_flags */
+
+#define CF_CHANGES_DATA		1
+#define CF_HAS_ROW_COUNT	2
+#define CF_STATUS_COMMAND	4
+#define CF_SHOW_TABLE_COMMAND	8
+
 /* Functions in sql_class.cc */
 
 void add_to_status(STATUS_VAR *to_var, STATUS_VAR *from_var);
-
+void add_diff_to_status(STATUS_VAR *to_var, STATUS_VAR *from_var,
+                        STATUS_VAR *dec_var);
 #endif /* MYSQL_SERVER */

sql/sql_lex.cc

@@ -168,7 +168,7 @@ void lex_start(THD *thd, const uchar *buf, uint length)
   lex->select_lex.group_list.empty();
   lex->select_lex.order_list.empty();
   lex->ignore_space=test(thd->variables.sql_mode & MODE_IGNORE_SPACE);
-  lex->sql_command= lex->orig_sql_command= SQLCOM_END;
+  lex->sql_command= SQLCOM_END;
   lex->duplicates= DUP_ERROR;
   lex->ignore= 0;
   lex->sphead= NULL;

sql/sql_lex.h

@@ -934,7 +934,7 @@ typedef struct st_lex : public Query_tables_list
     the variable can contain 0 or 1 for each nest level.
   */
   nesting_map allow_sum_func;
-  enum_sql_command sql_command, orig_sql_command;
+  enum_sql_command sql_command;
   thr_lock_type lock_option;
   enum SSL_type ssl_type;			/* defined in violite.h */
   enum my_lex_states next_state;

sql/sql_prepare.cc

@@ -1727,22 +1727,17 @@ static bool check_prepared_statement(Prepared_statement *stmt,
     res= mysql_test_insert_select(stmt, tables);
     break;
 
-  case SQLCOM_SHOW_DATABASES:
+    /*
+      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_STATUS:
-  case SQLCOM_SHOW_VARIABLES:
   case SQLCOM_SHOW_ENGINE_LOGS:
   case SQLCOM_SHOW_ENGINE_STATUS:
   case SQLCOM_SHOW_ENGINE_MUTEX:
-  case SQLCOM_SHOW_TABLES:
-  case SQLCOM_SHOW_OPEN_TABLES:
-  case SQLCOM_SHOW_CHARSETS:
-  case SQLCOM_SHOW_COLLATIONS:
-  case SQLCOM_SHOW_FIELDS:
-  case SQLCOM_SHOW_KEYS:
   case SQLCOM_SHOW_CREATE_DB:
   case SQLCOM_SHOW_GRANTS:
   case SQLCOM_DROP_TABLE:
@@ -1762,9 +1757,17 @@ static bool check_prepared_statement(Prepared_statement *stmt,
     break;
 
   default:
-    /* All other statements are not supported yet. */
-    my_message(ER_UNSUPPORTED_PS, ER(ER_UNSUPPORTED_PS), MYF(0));
-    goto error;
+    /*
+      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(text_protocol? FALSE : (send_prep_stmt(stmt, 0) ||

sql/sql_select.cc

@@ -551,9 +551,6 @@ JOIN::optimize()
     DBUG_RETURN(0);
   optimized= 1;
 
-  if (thd->lex->orig_sql_command != SQLCOM_SHOW_STATUS)
-    thd->status_var.last_query_cost= 0.0;
-
   row_limit= ((select_distinct || order || group_list) ? HA_POS_ERROR :
 	      unit->select_limit_cnt);
   /* select_limit is used to decide if we are likely to scan the whole table */
@@ -3875,10 +3872,8 @@ choose_plan(JOIN *join, table_map join_tables)
 
   /* 
     Store the cost of this query into a user variable
-    Don't update last_query_cost for 'show status' command
   */
-  if (join->thd->lex->orig_sql_command != SQLCOM_SHOW_STATUS)
-    join->thd->status_var.last_query_cost= join->best_read;
+  join->thd->status_var.last_query_cost= join->best_read;
   DBUG_VOID_RETURN;
 }
 

sql/sql_show.cc

@@ -2143,7 +2143,7 @@ bool schema_table_store_record(THD *thd, TABLE *table)
 void get_index_field_values(LEX *lex, INDEX_FIELD_VALUES *index_field_values)
 {
   const char *wild= lex->wild ? lex->wild->ptr() : NullS;
-  switch (lex->orig_sql_command) {
+  switch (lex->sql_command) {
   case SQLCOM_SHOW_DATABASES:
     index_field_values->db_value= wild;
     break;
@@ -2332,10 +2332,9 @@ int make_db_list(THD *thd, List<char> *files,
   /*
     This part of code is for SHOW TABLES, SHOW TABLE STATUS commands.
     idx_field_vals->db_value can't be 0 (see get_index_field_values()
-    function). lex->orig_sql_command can be not equal to SQLCOM_END
-    only in case of executing of SHOW commands.
+    function).
   */
-  if (lex->orig_sql_command != SQLCOM_END)
+  if (sql_command_flags[lex->sql_command] & CF_STATUS_COMMAND)
   {
     if (!my_strcasecmp(system_charset_info, information_schema_name.str,
                        idx_field_vals->db_value))
@@ -2414,12 +2413,6 @@ int get_all_tables(THD *thd, TABLE_LIST *tables, COND *cond)
   LINT_INIT(end);
   LINT_INIT(len);
 
-  /*
-    Let us set fake sql_command so views won't try to merge
-    themselves into main statement.
-  */
-  lex->sql_command= SQLCOM_SHOW_FIELDS;
-
   lex->reset_n_backup_query_tables_list(&query_tables_list_backup);
 
   /*
@@ -2442,8 +2435,16 @@ int get_all_tables(THD *thd, TABLE_LIST *tables, COND *cond)
       I_S tables will be done.
     */
     thd->temporary_tables= open_tables_state_backup.temporary_tables;
+    /*
+      Let us set fake sql_command so views won't try to merge
+      themselves into main statement. If we don't do this,
+      SELECT * from information_schema.xxxx will cause problems.
+      SQLCOM_SHOW_FIELDS is used because it satisfies 'only_view_structure()' 
+    */
+    lex->sql_command= SQLCOM_SHOW_FIELDS;
     res= open_normal_and_derived_tables(thd, show_table_list,
                                         MYSQL_LOCK_IGNORE_FLUSH);
+    lex->sql_command= save_sql_command;
     /*
       get_all_tables() returns 1 on failure and 0 on success thus
       return only these and not the result code of ::process_table()
@@ -2474,13 +2475,13 @@ int get_all_tables(THD *thd, TABLE_LIST *tables, COND *cond)
 
   partial_cond= make_cond_for_info_schema(cond, tables);
   it.rewind(); /* To get access to new elements in basis list */
+
+  /*
+    Below we generate error for non existing database.
+    (to save old behaviour for SHOW TABLES FROM db)
+  */
   while ((orig_base_name= base_name= it++) ||
-	 /*
-	   generate error for non existing database.
-	   (to save old behaviour for SHOW TABLES FROM db)
-	 */
-	 ((lex->orig_sql_command == SQLCOM_SHOW_TABLES ||
-           lex->orig_sql_command == SQLCOM_SHOW_TABLE_STATUS) &&
+         ((sql_command_flags[save_sql_command] & CF_SHOW_TABLE_COMMAND) &&
 	  (base_name= select_lex->db) && !bases.elements))
   {
 #ifndef NO_EMBEDDED_ACCESS_CHECKS
@@ -2521,7 +2522,8 @@ int get_all_tables(THD *thd, TABLE_LIST *tables, COND *cond)
         {
           if (schema_table_idx == SCH_TABLE_NAMES)
           {
-            if (lex->verbose || lex->orig_sql_command == SQLCOM_END)
+            if (lex->verbose ||
+                (sql_command_flags[save_sql_command] & CF_STATUS_COMMAND) == 0)
             {
               if (with_i_schema)
               {
@@ -2565,8 +2567,10 @@ int get_all_tables(THD *thd, TABLE_LIST *tables, COND *cond)
             TABLE_LIST *show_table_list= (TABLE_LIST*) sel.table_list.first;
             lex->all_selects_list= &sel;
             lex->derived_tables= 0;
+            lex->sql_command= SQLCOM_SHOW_FIELDS;
             res= open_normal_and_derived_tables(thd, show_table_list,
                                                 MYSQL_LOCK_IGNORE_FLUSH);
+            lex->sql_command= save_sql_command;
             /*
               We should use show_table_list->alias instead of 
               show_table_list->table_name because table_name
@@ -2876,7 +2880,7 @@ static int get_schema_column_record(THD *thd, struct st_table_list *tables,
 
   if (res)
   {
-    if (lex->orig_sql_command != SQLCOM_SHOW_FIELDS)
+    if (lex->sql_command != SQLCOM_SHOW_FIELDS)
     {
       /*
         I.e. we are in SELECT FROM INFORMATION_SCHEMA.COLUMS
@@ -2927,7 +2931,7 @@ static int get_schema_column_record(THD *thd, struct st_table_list *tables,
     col_access= get_column_grant(thd, &tables->grant, 
                                  base_name, file_name,
                                  field->field_name) & COL_ACLS;
-    if (lex->orig_sql_command != SQLCOM_SHOW_FIELDS  && 
+    if (lex->sql_command != SQLCOM_SHOW_FIELDS  &&
         !tables->schema_table && !col_access)
       continue;
     end= tmp;
@@ -2972,7 +2976,7 @@ static int get_schema_column_record(THD *thd, struct st_table_list *tables,
       table->field[5]->set_notnull();
     }
     else if (field->unireg_check == Field::NEXT_NUMBER ||
-             lex->orig_sql_command != SQLCOM_SHOW_FIELDS ||
+             lex->sql_command != SQLCOM_SHOW_FIELDS ||
              field->maybe_null())
       table->field[5]->set_null();                // Null as default
     else
@@ -3242,16 +3246,18 @@ bool store_schema_proc(THD *thd, TABLE *table, TABLE *proc_table,
   get_field(thd->mem_root, proc_table->field[11], &definer);
   if (!full_access)
     full_access= !strcmp(sp_user, definer.ptr());
-  if (!full_access && check_some_routine_access(thd, sp_db.ptr(), sp_name.ptr(),
-                                                proc_table->field[2]->val_int() ==
+  if (!full_access && check_some_routine_access(thd, sp_db.ptr(),
+                                                sp_name.ptr(),
+                                                proc_table->field[2]->
+                                                val_int() ==
                                                 TYPE_ENUM_PROCEDURE))
     return 0;
 
-  if (lex->orig_sql_command == SQLCOM_SHOW_STATUS_PROC &&
+  if (lex->sql_command == SQLCOM_SHOW_STATUS_PROC &&
       proc_table->field[2]->val_int() == TYPE_ENUM_PROCEDURE ||
-      lex->orig_sql_command == SQLCOM_SHOW_STATUS_FUNC &&
+      lex->sql_command == SQLCOM_SHOW_STATUS_FUNC &&
       proc_table->field[2]->val_int() == TYPE_ENUM_FUNCTION ||
-      lex->orig_sql_command == SQLCOM_END)
+      (sql_command_flags[lex->sql_command] & CF_STATUS_COMMAND) == 0)
   {
     restore_record(table, s->default_values);
     if (!wild || !wild[0] || !wild_compare(sp_name.ptr(), wild, 0))
@@ -3362,7 +3368,7 @@ static int get_schema_stat_record(THD *thd, struct st_table_list *tables,
   DBUG_ENTER("get_schema_stat_record");
   if (res)
   {
-    if (thd->lex->orig_sql_command != SQLCOM_SHOW_KEYS)
+    if (thd->lex->sql_command != SQLCOM_SHOW_KEYS)
     {
       /*
         I.e. we are in SELECT FROM INFORMATION_SCHEMA.STATISTICS
@@ -4153,7 +4159,7 @@ copy_event_to_schema_table(THD *thd, TABLE *sch_table, TABLE *event_table)
     optimized. It's guaranteed in case of SHOW EVENTS that the user
     has access.
   */
-  if (thd->lex->orig_sql_command != SQLCOM_SHOW_EVENTS &&
+  if (thd->lex->sql_command != SQLCOM_SHOW_EVENTS &&
       check_access(thd, EVENT_ACL, et.dbname.str, 0, 0, 1,
                    is_schema_db(et.dbname.str)))
     DBUG_RETURN(0);
@@ -4383,7 +4389,7 @@ int fill_schema_events(THD *thd, TABLE_LIST *tables, COND * /* cond */)
     If it's SHOW EVENTS then thd->lex->select_lex.db is guaranteed not to
     be NULL. Let's do an assert anyway.
   */
-  if (thd->lex->orig_sql_command == SQLCOM_SHOW_EVENTS)
+  if (thd->lex->sql_command == SQLCOM_SHOW_EVENTS)
   {
     DBUG_ASSERT(thd->lex->select_lex.db);
     if (check_access(thd, EVENT_ACL, thd->lex->select_lex.db, 0, 0, 0,
@@ -4411,7 +4417,7 @@ int fill_schema_events(THD *thd, TABLE_LIST *tables, COND * /* cond */)
                   will save use from doing a table scan and comparing
                   every single row's `db` with the schema which we show.
   */
-  if (thd->lex->orig_sql_command == SQLCOM_SHOW_EVENTS)
+  if (thd->lex->sql_command == SQLCOM_SHOW_EVENTS)
     ret= events_table_index_read_for_db(thd, schema_table, event_table);
   else
     ret= events_table_scan_all(thd, schema_table, event_table);
@@ -4477,7 +4483,7 @@ int fill_status(THD *thd, TABLE_LIST *tables, COND *cond)
                          (SHOW_VAR *)all_status_vars.buffer,
                          OPT_GLOBAL,
                          (lex->option_type == OPT_GLOBAL ?
-                          &tmp: &thd->status_var), "",tables->table);
+                          &tmp: thd->initial_status_var), "",tables->table);
   pthread_mutex_unlock(&LOCK_status);
   DBUG_RETURN(res);
 }
@@ -4670,8 +4676,8 @@ TABLE *create_schema_table(THD *thd, TABLE_LIST *table_list)
     schema_table        pointer to 'schema_tables' element
 
   RETURN
-   -1	errror
-    0	success
+   1	error
+   0	success
 */
 
 int make_old_format(THD *thd, ST_SCHEMA_TABLE *schema_table)
@@ -4994,7 +5000,7 @@ bool get_schema_tables_result(JOIN *join)
       break;
 
     TABLE_LIST *table_list= tab->table->pos_in_table_list;
-    if (table_list->schema_table && thd->fill_derived_tables())
+    if (table_list->schema_table && thd->fill_information_schema_tables())
     {
       bool is_subselect= (&lex->unit != lex->current_select->master_unit() &&
                           lex->current_select->master_unit()->item);

sql/sql_yacc.yy

@@ -2058,16 +2058,19 @@ sp_cursor_stmt:
 	  {
 	    Lex->sphead->reset_lex(YYTHD);
 
-	    /* We use statement here just be able to get a better
-	       error message. Using 'select' works too, but will then
-	       result in a generic "syntax error" if a non-select
-	       statement is given. */
+	    /*
+	      We use statement here just be able to get a better
+	      error message. Using 'select' works too, but will then
+	      result in a generic "syntax error" if a non-select
+	      statement is given.
+	    */
 	  }
 	  statement
 	  {
 	    LEX *lex= Lex;
 
-	    if (lex->sql_command != SQLCOM_SELECT)
+	    if (lex->sql_command != SQLCOM_SELECT &&
+	       !(sql_command_flags[lex->sql_command] & CF_STATUS_COMMAND))
 	    {
 	      my_message(ER_SP_BAD_CURSOR_QUERY, ER(ER_SP_BAD_CURSOR_QUERY),
                          MYF(0));
@@ -8062,16 +8065,14 @@ show_param:
          DATABASES wild_and_where
          {
            LEX *lex= Lex;
-           lex->sql_command= SQLCOM_SELECT;
-           lex->orig_sql_command= SQLCOM_SHOW_DATABASES;
+           lex->sql_command= SQLCOM_SHOW_DATABASES;
            if (prepare_schema_table(YYTHD, lex, 0, SCH_SCHEMATA))
              YYABORT;
          }
          | opt_full TABLES opt_db wild_and_where
            {
              LEX *lex= Lex;
-             lex->sql_command= SQLCOM_SELECT;
-             lex->orig_sql_command= SQLCOM_SHOW_TABLES;
+             lex->sql_command= SQLCOM_SHOW_TABLES;
              lex->select_lex.db= $3;
              if (prepare_schema_table(YYTHD, lex, 0, SCH_TABLE_NAMES))
                YYABORT;
@@ -8079,8 +8080,7 @@ show_param:
          | opt_full TRIGGERS_SYM opt_db wild_and_where
            {
              LEX *lex= Lex;
-             lex->sql_command= SQLCOM_SELECT;
-             lex->orig_sql_command= SQLCOM_SHOW_TRIGGERS;
+             lex->sql_command= SQLCOM_SHOW_TRIGGERS;
              lex->select_lex.db= $3;
              if (prepare_schema_table(YYTHD, lex, 0, SCH_TRIGGERS))
                YYABORT;
@@ -8088,8 +8088,7 @@ show_param:
          | EVENTS_SYM opt_db wild_and_where
            {
              LEX *lex= Lex;
-             lex->sql_command= SQLCOM_SELECT;
-             lex->orig_sql_command= SQLCOM_SHOW_EVENTS;
+             lex->sql_command= SQLCOM_SHOW_EVENTS;
              lex->select_lex.db= $2;
              if (prepare_schema_table(YYTHD, lex, 0, SCH_EVENTS))
                YYABORT;
@@ -8106,8 +8105,7 @@ show_param:
          | TABLE_SYM STATUS_SYM opt_db wild_and_where
            {
              LEX *lex= Lex;
-             lex->sql_command= SQLCOM_SELECT;
-             lex->orig_sql_command= SQLCOM_SHOW_TABLE_STATUS;
+             lex->sql_command= SQLCOM_SHOW_TABLE_STATUS;
              lex->select_lex.db= $3;
              if (prepare_schema_table(YYTHD, lex, 0, SCH_TABLES))
                YYABORT;
@@ -8115,8 +8113,7 @@ show_param:
         | OPEN_SYM TABLES opt_db wild_and_where
 	  {
 	    LEX *lex= Lex;
-            lex->sql_command= SQLCOM_SELECT;
-            lex->orig_sql_command= SQLCOM_SHOW_OPEN_TABLES;
+            lex->sql_command= SQLCOM_SHOW_OPEN_TABLES;
 	    lex->select_lex.db= $3;
             if (prepare_schema_table(YYTHD, lex, 0, SCH_OPEN_TABLES))
               YYABORT;
@@ -8125,16 +8122,14 @@ show_param:
 	  {
 	    LEX *lex= Lex;
 	    WARN_DEPRECATED(yythd, "5.2", "SHOW PLUGIN", "'SHOW PLUGINS'");
-            lex->sql_command= SQLCOM_SELECT;
-            lex->orig_sql_command= SQLCOM_SHOW_PLUGINS;
+            lex->sql_command= SQLCOM_SHOW_PLUGINS;
             if (prepare_schema_table(YYTHD, lex, 0, SCH_PLUGINS))
               YYABORT;
 	  }
         | PLUGINS_SYM
 	  {
 	    LEX *lex= Lex;
-            lex->sql_command= SQLCOM_SELECT;
-            lex->orig_sql_command= SQLCOM_SHOW_PLUGINS;
+            lex->sql_command= SQLCOM_SHOW_PLUGINS;
             if (prepare_schema_table(YYTHD, lex, 0, SCH_PLUGINS))
               YYABORT;
 	  }
@@ -8147,8 +8142,7 @@ show_param:
 	| opt_full COLUMNS from_or_in table_ident opt_db wild_and_where
 	  {
  	    LEX *lex= Lex;
-	    lex->sql_command= SQLCOM_SELECT;
-	    lex->orig_sql_command= SQLCOM_SHOW_FIELDS;
+	    lex->sql_command= SQLCOM_SHOW_FIELDS;
 	    if ($5)
 	      $4->change_db($5);
 	    if (prepare_schema_table(YYTHD, lex, $4, SCH_COLUMNS))
@@ -8180,8 +8174,7 @@ show_param:
         | keys_or_index from_or_in table_ident opt_db where_clause
           {
             LEX *lex= Lex;
-            lex->sql_command= SQLCOM_SELECT;
-            lex->orig_sql_command= SQLCOM_SHOW_KEYS;
+            lex->sql_command= SQLCOM_SHOW_KEYS;
 	    if ($4)
 	      $3->change_db($4);
             if (prepare_schema_table(YYTHD, lex, $3, SCH_STATISTICS))
@@ -8202,7 +8195,6 @@ show_param:
 	  {
 	    LEX *lex=Lex;
 	    lex->sql_command= SQLCOM_SHOW_STORAGE_ENGINES;
-            lex->orig_sql_command= SQLCOM_SHOW_AUTHORS;
             if (prepare_schema_table(YYTHD, lex, 0, SCH_ENGINES))
               YYABORT;
 	  }
@@ -8232,8 +8224,7 @@ show_param:
         | opt_var_type STATUS_SYM wild_and_where
           {
             LEX *lex= Lex;
-            lex->sql_command= SQLCOM_SELECT;
-            lex->orig_sql_command= SQLCOM_SHOW_STATUS;
+            lex->sql_command= SQLCOM_SHOW_STATUS;
             lex->option_type= $1;
             if (prepare_schema_table(YYTHD, lex, 0, SCH_STATUS))
               YYABORT;
@@ -8267,8 +8258,7 @@ show_param:
         | opt_var_type  VARIABLES wild_and_where
 	  {
             LEX *lex= Lex;
-            lex->sql_command= SQLCOM_SELECT;
-            lex->orig_sql_command= SQLCOM_SHOW_VARIABLES;
+            lex->sql_command= SQLCOM_SHOW_VARIABLES;
             lex->option_type= $1;
             if (prepare_schema_table(YYTHD, lex, 0, SCH_VARIABLES))
               YYABORT;
@@ -8276,16 +8266,14 @@ show_param:
         | charset wild_and_where
           {
             LEX *lex= Lex;
-            lex->sql_command= SQLCOM_SELECT;
-            lex->orig_sql_command= SQLCOM_SHOW_CHARSETS;
+            lex->sql_command= SQLCOM_SHOW_CHARSETS;
             if (prepare_schema_table(YYTHD, lex, 0, SCH_CHARSETS))
               YYABORT;
           }
         | COLLATION_SYM wild_and_where
           {
             LEX *lex= Lex;
-            lex->sql_command= SQLCOM_SELECT;
-            lex->orig_sql_command= SQLCOM_SHOW_COLLATIONS;
+            lex->sql_command= SQLCOM_SHOW_COLLATIONS;
             if (prepare_schema_table(YYTHD, lex, 0, SCH_COLLATIONS))
               YYABORT;
           }
@@ -8391,8 +8379,7 @@ show_param:
 	| PROCEDURE STATUS_SYM wild_and_where
 	  {
             LEX *lex= Lex;
-            lex->sql_command= SQLCOM_SELECT;
-            lex->orig_sql_command= SQLCOM_SHOW_STATUS_PROC;
+            lex->sql_command= SQLCOM_SHOW_STATUS_PROC;
 	    if (!sp_add_to_query_tables(YYTHD, lex, "mysql", "proc", TL_READ))
 	      YYABORT;
             if (prepare_schema_table(YYTHD, lex, 0, SCH_PROCEDURES))
@@ -8401,8 +8388,7 @@ show_param:
 	| FUNCTION_SYM STATUS_SYM wild_and_where
 	  {
             LEX *lex= Lex;
-            lex->sql_command= SQLCOM_SELECT;
-            lex->orig_sql_command= SQLCOM_SHOW_STATUS_FUNC;
+            lex->sql_command= SQLCOM_SHOW_STATUS_FUNC;
 	    if (!sp_add_to_query_tables(YYTHD, lex, "mysql", "proc", TL_READ))
 	      YYABORT;
             if (prepare_schema_table(YYTHD, lex, 0, SCH_PROCEDURES))
@@ -8497,8 +8483,7 @@ describe:
           lex->lock_option= TL_READ;
           mysql_init_select(lex);
           lex->current_select->parsing_place= SELECT_LIST;
-          lex->sql_command= SQLCOM_SELECT;
-          lex->orig_sql_command= SQLCOM_SHOW_FIELDS;
+          lex->sql_command= SQLCOM_SHOW_FIELDS;
           lex->select_lex.db= 0;
           lex->verbose= 0;
           if (prepare_schema_table(YYTHD, lex, $2, SCH_COLUMNS))

sql/structs.h

@@ -180,7 +180,7 @@ typedef struct user_resources {
   uint questions;
   /*
      Maximum number of updating statements per hour (which statements are
-     updating is defined by uc_update_queries array).
+     updating is defined by sql_command_flags array).
   */
   uint updates;
   /* Maximum number of connections established per hour. */