WL#2126 - Multi_read_range.

Added the required structures and functions for
handing over multiple key ranges to the table handler.

include/my_base.h

@@ -370,6 +370,15 @@ enum data_file_type {
 
 /* For key ranges */
 
+#define NO_MIN_RANGE	1
+#define NO_MAX_RANGE	2
+#define NEAR_MIN	4
+#define NEAR_MAX	8
+#define UNIQUE_RANGE	16
+#define EQ_RANGE	32
+#define NULL_RANGE	64
+#define GEOM_FLAG      128
+
 typedef struct st_key_range
 {
   const byte *key;
@@ -377,6 +386,14 @@ typedef struct st_key_range
   enum ha_rkey_function flag;
 } key_range;
 
+typedef struct st_key_multi_range
+{
+  key_range start_key;
+  key_range end_key;
+  char  *ptr;                 /* Free to use by caller (ptr to row etc) */
+  uint  range_flag;           /* key range flags see above */
+} KEY_MULTI_RANGE;
+
 
 /* For number of records */
 #ifdef BIG_TABLES

sql/handler.cc

@@ -1685,6 +1685,131 @@ int ha_table_exists(THD* thd, const char* db, const char* name)
 #endif
 
 
+/*
+  Read the first row of a multi-range set.
+
+  SYNOPSIS
+    read_multi_range_first()
+    found_range_p       Returns a pointer to the element in 'ranges' that
+                        corresponds to the returned row.
+    ranges              An array of KEY_MULTI_RANGE range descriptions.
+    range_count         Number of ranges in 'ranges'.
+    sorted		If result should be sorted per key.
+    buffer              A HANDLER_BUFFER for internal handler usage.
+
+  NOTES
+    Record is read into table->record[0].
+    *found_range_p returns a valid value only if read_multi_range_first()
+    returns 0.
+    Sorting is done within each range. If you want an overall sort, enter
+    'ranges' with sorted ranges.
+
+  RETURN
+    0			OK, found a row
+    HA_ERR_END_OF_FILE	No rows in range
+    #			Error code
+*/
+
+int handler::read_multi_range_first(KEY_MULTI_RANGE **found_range_p,
+                                    KEY_MULTI_RANGE *ranges, uint range_count,
+                                    bool sorted, HANDLER_BUFFER *buffer)
+{
+  int result= HA_ERR_END_OF_FILE;
+  DBUG_ENTER("handler::read_multi_range_first");
+  multi_range_sorted= sorted;
+  multi_range_buffer= buffer;
+
+  for (multi_range_curr= ranges, multi_range_end= ranges + range_count;
+       multi_range_curr < multi_range_end;
+       multi_range_curr++)
+  {
+    result= read_range_first(multi_range_curr->start_key.length ?
+                             &multi_range_curr->start_key : 0,
+                             multi_range_curr->end_key.length ?
+                             &multi_range_curr->end_key : 0,
+                             test(multi_range_curr->range_flag & EQ_RANGE),
+                             multi_range_sorted);
+    if (result != HA_ERR_END_OF_FILE)
+      break;
+  }
+
+  *found_range_p= multi_range_curr;
+  DBUG_PRINT("exit",("result %d", result));
+  DBUG_RETURN(result);
+}
+
+
+/*
+  Read the next row of a multi-range set.
+
+  SYNOPSIS
+    read_multi_range_next()
+    found_range_p       Returns a pointer to the element in 'ranges' that
+                        corresponds to the returned row.
+
+  NOTES
+    Record is read into table->record[0].
+    *found_range_p returns a valid value only if read_multi_range_next()
+    returns 0.
+
+  RETURN
+    0			OK, found a row
+    HA_ERR_END_OF_FILE	No (more) rows in range
+    #			Error code
+*/
+
+int handler::read_multi_range_next(KEY_MULTI_RANGE **found_range_p)
+{
+  int result;
+  DBUG_ENTER("handler::read_multi_range_next");
+
+  /* We should not be called after the last call returned EOF. */
+  DBUG_ASSERT(multi_range_curr < multi_range_end);
+
+  do
+  {
+    /* Save a call if there can be only one row in range. */
+    if (multi_range_curr->range_flag != (UNIQUE_RANGE | EQ_RANGE))
+    {
+      result= read_range_next();
+
+      /* On success or non-EOF errors jump to the end. */
+      if (result != HA_ERR_END_OF_FILE)
+        break;
+    }
+    else
+    {
+      /*
+        We need to set this for the last range only, but checking this
+        condition is more expensive than just setting the result code.
+      */
+      result= HA_ERR_END_OF_FILE;
+    }
+
+    /* Try the next range(s) until one matches a record. */
+    for (multi_range_curr++;
+         multi_range_curr < multi_range_end;
+         multi_range_curr++)
+    {
+      result= read_range_first(multi_range_curr->start_key.length ?
+                               &multi_range_curr->start_key : 0,
+                               multi_range_curr->end_key.length ?
+                               &multi_range_curr->end_key : 0,
+                               test(multi_range_curr->range_flag & EQ_RANGE),
+                               multi_range_sorted);
+      if (result != HA_ERR_END_OF_FILE)
+        break;
+    }
+  }
+  while ((result == HA_ERR_END_OF_FILE) &&
+         (multi_range_curr < multi_range_end));
+
+  *found_range_p= multi_range_curr;
+  DBUG_PRINT("exit",("handler::read_multi_range_next: result %d", result));
+  DBUG_RETURN(result);
+}
+
+
 /*
   Read first row between two ranges.
   Store ranges for future calls to read_range_next

sql/handler.h

@@ -76,6 +76,7 @@
 #define HA_FILE_BASED	       (1 << 26)
 #define HA_NO_VARCHAR	       (1 << 27)
 #define HA_CAN_BIT_FIELD       (1 << 28) /* supports bit fields */
+#define HA_NEED_READ_RANGE_BUFFER (1 << 29) /* for read_multi_range */
 
 
 /* bits in index_flags(index_number) for what you can do with index */
@@ -276,6 +277,21 @@ typedef struct st_ha_check_opt
 } HA_CHECK_OPT;
 
 
+/*
+  This is a buffer area that the handler can use to store rows.
+  'end_of_used_area' should be kept updated after calls to
+  read-functions so that other parts of the code can use the
+  remaining area (until next read calls is issued).
+*/
+
+typedef struct st_handler_buffer
+{
+  const byte *buffer;         /* Buffer one can start using */
+  const byte *buffer_end;     /* End of buffer */
+  byte *end_of_used_area;     /* End of area that was used by handler */
+} HANDLER_BUFFER;
+
+
 class handler :public Sql_alloc
 {
  protected:
@@ -310,6 +326,12 @@ class handler :public Sql_alloc
   time_t check_time;
   time_t update_time;
 
+  /* The following are for read_multi_range */
+  bool multi_range_sorted;
+  KEY_MULTI_RANGE *multi_range_curr;
+  KEY_MULTI_RANGE *multi_range_end;
+  HANDLER_BUFFER *multi_range_buffer;
+
   /* The following are for read_range() */
   key_range save_end_range, *end_range;
   KEY_PART_INFO *range_key_part;
@@ -421,6 +443,10 @@ class handler :public Sql_alloc
   virtual int index_next_same(byte *buf, const byte *key, uint keylen);
   virtual int index_read_last(byte * buf, const byte * key, uint key_len)
    { return (my_errno=HA_ERR_WRONG_COMMAND); }
+  virtual int read_multi_range_first(KEY_MULTI_RANGE **found_range_p,
+                                     KEY_MULTI_RANGE *ranges, uint range_count,
+                                     bool sorted, HANDLER_BUFFER *buffer);
+  virtual int read_multi_range_next(KEY_MULTI_RANGE **found_range_p);
   virtual int read_range_first(const key_range *start_key,
                                const key_range *end_key,
                                bool eq_range, bool sorted);

sql/mysqld.cc

@@ -4141,7 +4141,7 @@ enum options_mysqld
   OPT_MAX_SEEKS_FOR_KEY, OPT_MAX_TMP_TABLES, OPT_MAX_USER_CONNECTIONS,
   OPT_MAX_LENGTH_FOR_SORT_DATA,
   OPT_MAX_WRITE_LOCK_COUNT, OPT_BULK_INSERT_BUFFER_SIZE,
-  OPT_MAX_ERROR_COUNT, OPT_MYISAM_DATA_POINTER_SIZE,
+  OPT_MAX_ERROR_COUNT, OPT_MULTI_RANGE_COUNT, OPT_MYISAM_DATA_POINTER_SIZE,
   OPT_MYISAM_BLOCK_SIZE, OPT_MYISAM_MAX_EXTRA_SORT_FILE_SIZE,
   OPT_MYISAM_MAX_SORT_FILE_SIZE, OPT_MYISAM_SORT_BUFFER_SIZE,
   OPT_NET_BUFFER_LENGTH, OPT_NET_RETRY_COUNT,
@@ -5137,6 +5137,11 @@ The minimum value for this variable is 4096.",
    "After this many write locks, allow some read locks to run in between.",
    (gptr*) &max_write_lock_count, (gptr*) &max_write_lock_count, 0, GET_ULONG,
    REQUIRED_ARG, ~0L, 1, ~0L, 0, 1, 0},
+  {"multi_range_count", OPT_MULTI_RANGE_COUNT,
+   "Number of key ranges to request at once.",
+   (gptr*) &global_system_variables.multi_range_count,
+   (gptr*) &max_system_variables.multi_range_count, 0,
+   GET_ULONG, REQUIRED_ARG, 256, 1, ~0L, 0, 1, 0},
   {"myisam_block_size", OPT_MYISAM_BLOCK_SIZE,
    "Block size to be used for MyISAM index pages.",
    (gptr*) &opt_myisam_block_size,

sql/opt_range.cc

@@ -712,7 +712,7 @@ QUICK_SELECT_I::QUICK_SELECT_I()
 
 QUICK_RANGE_SELECT::QUICK_RANGE_SELECT(THD *thd, TABLE *table, uint key_nr,
                                        bool no_alloc, MEM_ROOT *parent_alloc)
-  :dont_free(0),error(0),free_file(0),cur_range(NULL),range(0)
+  :dont_free(0),error(0),free_file(0),cur_range(NULL),range(0),in_range(0)
 {
   sorted= 0;
   index= key_nr;
@@ -720,6 +720,13 @@ QUICK_RANGE_SELECT::QUICK_RANGE_SELECT(THD *thd, TABLE *table, uint key_nr,
   key_part_info= head->key_info[index].key_part;
   my_init_dynamic_array(&ranges, sizeof(QUICK_RANGE*), 16, 16);
 
+  /* 'thd' is not accessible in QUICK_RANGE_SELECT::get_next_init(). */
+  multi_range_bufsiz= thd->variables.read_rnd_buff_size;
+  multi_range_count= thd->variables.multi_range_count;
+  multi_range_length= 0;
+  multi_range= NULL;
+  multi_range_buff= NULL;
+
   if (!no_alloc && !parent_alloc)
   {
     // Allocates everything through the internal memroot
@@ -736,6 +743,10 @@ QUICK_RANGE_SELECT::QUICK_RANGE_SELECT(THD *thd, TABLE *table, uint key_nr,
 int QUICK_RANGE_SELECT::init()
 {
   DBUG_ENTER("QUICK_RANGE_SELECT::init");
+
+  if ((error= get_next_init()))
+    DBUG_RETURN(error);
+
   if (file->inited == handler::NONE)
     DBUG_RETURN(error= file->ha_index_init(index));
   error= 0;
@@ -771,6 +782,10 @@ QUICK_RANGE_SELECT::~QUICK_RANGE_SELECT()
     delete_dynamic(&ranges); /* ranges are allocated in alloc */
     free_root(&alloc,MYF(0));
   }
+  if (multi_range)
+    my_free((char*) multi_range, MYF(0));
+  if (multi_range_buff)
+    my_free((char*) multi_range_buff, MYF(0));
   DBUG_VOID_RETURN;
 }
 
@@ -5872,58 +5887,178 @@ int QUICK_ROR_UNION_SELECT::get_next()
   DBUG_RETURN(error);
 }
 
-	/* get next possible record using quick-struct */
+
+/*
+  Initialize data structures needed by get_next().
+
+  SYNOPSIS
+    QUICK_RANGE_SELECT::get_next_init()
+
+  DESCRIPTION
+    This is called from get_next() at its first call for an object.
+    It allocates memory buffers and sets size variables.
+
+  RETURN
+    0           OK.
+    != 0        Error.
+*/
+
+int QUICK_RANGE_SELECT::get_next_init(void)
+{
+  uint  mrange_bufsiz;
+  byte  *mrange_buff;
+  DBUG_ENTER("QUICK_RANGE_SELECT::get_next_init");
+
+  /* Do not allocate the buffers twice. */
+  if (multi_range_length)
+  {
+    DBUG_ASSERT(multi_range_length == min(multi_range_count, ranges.elements));
+    DBUG_RETURN(0);
+  }
+
+  /* If the ranges are not yet initialized, wait for the next call. */
+  if (! ranges.elements)
+  {
+    DBUG_RETURN(0);
+  }
+
+  /*
+    Allocate the ranges array.
+  */
+  multi_range_length= min(multi_range_count, ranges.elements);
+  DBUG_ASSERT(multi_range_length > 0);
+  while (multi_range_length && ! (multi_range= (KEY_MULTI_RANGE*)
+                                  my_malloc(multi_range_length *
+                                            sizeof(KEY_MULTI_RANGE),
+                                            MYF(MY_WME))))
+  {
+    /* Try to shrink the buffers until it is 0. */
+    multi_range_length/= 2;
+  }
+  if (! multi_range)
+  {
+    multi_range_length= 0;
+    DBUG_RETURN(HA_ERR_OUT_OF_MEM);
+  }
+
+  /*
+    Allocate the handler buffer if necessary.
+  */
+  if (file->table_flags() & HA_NEED_READ_RANGE_BUFFER)
+  {
+    mrange_bufsiz= min(multi_range_bufsiz,
+                       QUICK_SELECT_I::records * head->reclength);
+
+    while (mrange_bufsiz &&
+           ! my_multi_malloc(MYF(MY_WME),
+                             &multi_range_buff, sizeof(*multi_range_buff),
+                             &mrange_buff, mrange_bufsiz,
+                             NullS))
+    {
+      /* Try to shrink the buffers until both are 0. */
+      mrange_bufsiz/= 2;
+    }
+    if (! multi_range_buff)
+    {
+      my_free((char*) multi_range, MYF(0));
+      multi_range= NULL;
+      multi_range_length= 0;
+      DBUG_RETURN(HA_ERR_OUT_OF_MEM);
+    }
+
+    /* Initialize the handler buffer. */
+    multi_range_buff->buffer= mrange_buff;
+    multi_range_buff->buffer_end= mrange_buff + mrange_bufsiz;
+    multi_range_buff->end_of_used_area= mrange_buff;
+  }
+
+  /* Initialize the current QUICK_RANGE pointer. */
+  cur_range= (QUICK_RANGE**) ranges.buffer;
+  DBUG_RETURN(0);
+}
+
+
+/*
+  Get next possible record using quick-struct.
+
+  SYNOPSIS
+    QUICK_RANGE_SELECT::get_next()
+
+  NOTES
+    Record is read into table->record[0]
+
+  RETURN
+    0			Found row
+    HA_ERR_END_OF_FILE	No (more) rows in range
+    #			Error code
+*/
 
 int QUICK_RANGE_SELECT::get_next()
 {
+  int             result;
+  KEY_MULTI_RANGE *mrange;
+  key_range       *start_key;
+  key_range       *end_key;
   DBUG_ENTER("QUICK_RANGE_SELECT::get_next");
+  DBUG_ASSERT(multi_range_length && multi_range &&
+              (cur_range >= (QUICK_RANGE**) ranges.buffer) &&
+              (cur_range <= (QUICK_RANGE**) ranges.buffer + ranges.elements));
 
   for (;;)
   {
-    int result;
-    key_range start_key, end_key;
-    if (range)
+    if (in_range)
     {
-      // Already read through key
-      result= file->read_range_next();
+      /* We did already start to read this key. */
+      result= file->read_multi_range_next(&mrange);
       if (result != HA_ERR_END_OF_FILE)
+      {
+        in_range= ! result;
 	DBUG_RETURN(result);
+      }
     }
 
-    if (!cur_range)
-      range= *(cur_range= (QUICK_RANGE**) ranges.buffer);
-    else
-      range=
-        (cur_range == ((QUICK_RANGE**) ranges.buffer + ranges.elements - 1)) ?
-        (QUICK_RANGE*) 0 : *(++cur_range);
-
-    if (!range)
-      DBUG_RETURN(HA_ERR_END_OF_FILE);		// All ranges used
-
-    start_key.key=    (const byte*) range->min_key;
-    start_key.length= range->min_length;
-    start_key.flag=   ((range->flag & NEAR_MIN) ? HA_READ_AFTER_KEY :
-		       (range->flag & EQ_RANGE) ?
-		       HA_READ_KEY_EXACT : HA_READ_KEY_OR_NEXT);
-    end_key.key=      (const byte*) range->max_key;
-    end_key.length=   range->max_length;
-    /*
-      We use READ_AFTER_KEY here because if we are reading on a key
-      prefix we want to find all keys with this prefix
-    */
-    end_key.flag=     (range->flag & NEAR_MAX ? HA_READ_BEFORE_KEY :
-		       HA_READ_AFTER_KEY);
+    uint count= min(multi_range_length, ranges.elements -
+                    (cur_range - (QUICK_RANGE**) ranges.buffer));
+    if (count == 0)
+    {
+      /* Ranges have already been used up before. None is left for read. */
+      in_range= FALSE;
+      DBUG_RETURN(HA_ERR_END_OF_FILE);
+    }
+    KEY_MULTI_RANGE *mrange_slot, *mrange_end;
+    for (mrange_slot= multi_range, mrange_end= mrange_slot+count;
+         mrange_slot < mrange_end;
+         mrange_slot++)
+    {
+      start_key= &mrange_slot->start_key;
+      end_key= &mrange_slot->end_key;
+      range= *(cur_range++);
+
+      start_key->key=    (const byte*) range->min_key;
+      start_key->length= range->min_length;
+      start_key->flag=   ((range->flag & NEAR_MIN) ? HA_READ_AFTER_KEY :
+                          (range->flag & EQ_RANGE) ?
+                          HA_READ_KEY_EXACT : HA_READ_KEY_OR_NEXT);
+      end_key->key=      (const byte*) range->max_key;
+      end_key->length=   range->max_length;
+      /*
+        We use HA_READ_AFTER_KEY here because if we are reading on a key
+        prefix. We want to find all keys with this prefix.
+      */
+      end_key->flag=     (range->flag & NEAR_MAX ? HA_READ_BEFORE_KEY :
+                          HA_READ_AFTER_KEY);
 
-    result= file->read_range_first(range->min_length ? &start_key : 0,
-				   range->max_length ? &end_key : 0,
-                                   test(range->flag & EQ_RANGE),
-				   sorted);
-    if (range->flag == (UNIQUE_RANGE | EQ_RANGE))
-      range=0;				// Stop searching
+      mrange_slot->range_flag= range->flag;
+    }
 
+    result= file->read_multi_range_first(&mrange, multi_range, count,
+                                         sorted, multi_range_buff);
     if (result != HA_ERR_END_OF_FILE)
+    {
+      in_range= ! result;
       DBUG_RETURN(result);
-    range=0;				// No matching rows; go to next range
+    }
+    in_range= FALSE; /* No matching rows; go to next set of ranges. */
   }
 }
 
@@ -5974,15 +6109,14 @@ int QUICK_RANGE_SELECT::get_next_prefix(uint prefix_length, byte *cur_prefix)
         DBUG_RETURN(result);
     }
 
-    if (!cur_range)
-      range= *(cur_range= (QUICK_RANGE**) ranges.buffer); /* First range. */
-    else
-      range=
-        (cur_range == ((QUICK_RANGE**) ranges.buffer + ranges.elements - 1)) ?
-        (QUICK_RANGE*) 0 : *(++cur_range);                /* Next range. */
-
-    if (!range)
-      DBUG_RETURN(HA_ERR_END_OF_FILE);		// All ranges used
+    uint count= ranges.elements - (cur_range - (QUICK_RANGE**) ranges.buffer);
+    if (count == 0)
+    {
+      /* Ranges have already been used up before. None is left for read. */
+      range= 0;
+      DBUG_RETURN(HA_ERR_END_OF_FILE);
+    }
+    range= *(cur_range++);
 
     start_key.key=    (const byte*) range->min_key;
     start_key.length= min(range->min_length, prefix_length);
@@ -6030,15 +6164,14 @@ int QUICK_RANGE_SELECT_GEOM::get_next()
 	DBUG_RETURN(result);
     }
 
-   if (!cur_range)
-      range= *(cur_range= (QUICK_RANGE**) ranges.buffer);
-    else
-      range=
-        (cur_range == ((QUICK_RANGE**) ranges.buffer + ranges.elements - 1)) ?
-        (QUICK_RANGE*) 0 : *(++cur_range);
-
-    if (!range)
-      DBUG_RETURN(HA_ERR_END_OF_FILE);		// All ranges used
+    uint count= ranges.elements - (cur_range - (QUICK_RANGE**) ranges.buffer);
+    if (count == 0)
+    {
+      /* Ranges have already been used up before. None is left for read. */
+      range= 0;
+      DBUG_RETURN(HA_ERR_END_OF_FILE);
+    }
+    range= *(cur_range++);
 
     result= file->index_read(record,
 			     (byte*) range->min_key,

sql/opt_range.h

@@ -24,16 +24,6 @@
 #pragma interface			/* gcc class implementation */
 #endif
 
-#define NO_MIN_RANGE	1
-#define NO_MAX_RANGE	2
-#define NEAR_MIN	4
-#define NEAR_MAX	8
-#define UNIQUE_RANGE	16
-#define EQ_RANGE	32
-#define NULL_RANGE	64
-#define GEOM_FLAG      128
-
-
 typedef struct st_key_part {
   uint16           key,part, store_length, length;
   uint8            null_bit;
@@ -135,9 +125,24 @@ class QUICK_SELECT_I
   */
   virtual int  reset(void) = 0;
 
+  /*
+    Initialize get_next() for row retrieval.
+    SYNOPSIS
+      get_next_init()
+
+    get_next_init() must be called before the first get_next().
+    If get_next_init() call fails get_next() must not be called.
+
+    RETURN
+      0      OK
+      other  Error code
+  */
+  virtual int  get_next_init() { return false; }
+  virtual int  get_next() = 0;   /* get next record to retrieve */
+
   /* Range end should be called when we have looped over the whole index */
   virtual void range_end() {}
-  virtual int  get_next() = 0;   /* get next record to retrieve */
+
   virtual bool reverse_sorted() = 0;
   virtual bool unique_key_range() { return false; }
 
@@ -236,6 +241,14 @@ class QUICK_RANGE_SELECT : public QUICK_SELECT_I
     closed no later then this quick select is deleted.
   */
   bool free_file;
+  bool in_range;
+  uint multi_range_count; /* copy from thd->variables.multi_range_count */
+  uint multi_range_length; /* the allocated length for the array */
+  uint multi_range_bufsiz; /* copy from thd->variables.read_rnd_buff_size */
+  KEY_MULTI_RANGE *multi_range; /* the multi-range array (allocated and
+                                       freed by QUICK_RANGE_SELECT) */
+  HANDLER_BUFFER *multi_range_buff; /* the handler buffer (allocated and
+                                       freed by QUICK_RANGE_SELECT) */
 
 protected:
   friend class TRP_ROR_INTERSECT;
@@ -270,18 +283,19 @@ class QUICK_RANGE_SELECT : public QUICK_SELECT_I
                      MEM_ROOT *parent_alloc=NULL);
   ~QUICK_RANGE_SELECT();
 
+  int init();
   int reset(void)
   {
     next=0;
     range= NULL;
-    cur_range= NULL;
+    cur_range= (QUICK_RANGE**) ranges.buffer;
     /*
       Note: in opt_range.cc there are places where it is assumed that this
       function always succeeds 
     */
     return 0;
   }
-  int init();
+  int get_next_init(void);
   int get_next();
   void range_end();
   int get_next_prefix(uint prefix_length, byte *cur_prefix);
@@ -296,6 +310,13 @@ class QUICK_RANGE_SELECT : public QUICK_SELECT_I
 #ifndef DBUG_OFF
   void dbug_dump(int indent, bool verbose);
 #endif
+  QUICK_RANGE_SELECT(const QUICK_RANGE_SELECT& org) : QUICK_SELECT_I()
+  {
+    bcopy(&org, this, sizeof(*this));
+    multi_range_length= 0;
+    multi_range= NULL;
+    multi_range_buff= NULL;
+  }
 };
 
 

sql/records.cc

@@ -100,11 +100,19 @@ void init_read_record(READ_RECORD *info,THD *thd, TABLE *table,
   }
   else if (select && select->quick)
   {
+    int error;
     DBUG_PRINT("info",("using rr_quick"));
 
     if (!table->file->inited)
       table->file->ha_index_init(select->quick->index);
     info->read_record=rr_quick;
+
+    if ((error= select->quick->get_next_init()))
+    {
+      /* Cannot return error code here. Instead print to error log. */
+      table->file->print_error(error,MYF(ME_NOREFRESH));
+      thd->fatal_error();
+    }
   }
   else if (table->sort.record_pointers)
   {

sql/set_var.cc

@@ -259,6 +259,8 @@ sys_var_thd_ulong	sys_max_tmp_tables("max_tmp_tables",
 					   &SV::max_tmp_tables);
 sys_var_long_ptr	sys_max_write_lock_count("max_write_lock_count",
 						 &max_write_lock_count);
+sys_var_thd_ulong       sys_multi_range_count("multi_range_count",
+                                              &SV::multi_range_count);
 sys_var_long_ptr	sys_myisam_data_pointer_size("myisam_data_pointer_size",
                                                     &myisam_data_pointer_size);
 sys_var_thd_ulonglong	sys_myisam_max_extra_sort_file_size("myisam_max_extra_sort_file_size", &SV::myisam_max_extra_sort_file_size, fix_myisam_max_extra_sort_file_size, 1);

sql/sql_class.h

@@ -388,6 +388,7 @@ struct system_variables
   ulong max_sort_length;
   ulong max_tmp_tables;
   ulong max_insert_delayed_threads;
+  ulong multi_range_count;
   ulong myisam_repair_threads;
   ulong myisam_sort_buff_size;
   ulong net_buffer_length;