bk commit into 5.0 tree (sergefp:1.1999) BUG#14940

[Sergey Petrunia]

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ChangeSet
  1.1999 05/11/24 12:54:46 sergefp@stripped +2 -0
  BUG#14940 part1: When evaluating cost of using one of indexes in union-index_merge,
don't 
  save the received #records estimate as full cost of accessing the entire table. 

  sql/table.h
    1.120 05/11/24 12:54:40 sergefp@stripped +7 -1
    Added comments.

  sql/opt_range.cc
    1.199 05/11/24 12:54:40 sergefp@stripped +22 -10
    BUG#14940 part1: When evaluating cost of using one of indexes in union-index_merge,
don't 
    save the received #records estimate as full cost of accessing the entire table.

# This is a BitKeeper patch.  What follows are the unified diffs for the
# set of deltas contained in the patch.  The rest of the patch, the part
# that BitKeeper cares about, is below these diffs.
# User:	sergefp
# Host:	newbox.mylan
# Root:	/home/psergey/mysql-5.0-csc4856-r4

--- 1.198/sql/opt_range.cc	2005-11-20 21:47:00 +03:00
+++ 1.199/sql/opt_range.cc	2005-11-24 12:54:40 +03:00
@@ -369,7 +369,8 @@
 static SEL_TREE *get_mm_tree(PARAM *param,COND *cond);
 
 static bool is_key_scan_ror(PARAM *param, uint keynr, uint8 nparts);
-static ha_rows check_quick_select(PARAM *param,uint index,SEL_ARG *key_tree);
+static ha_rows check_quick_select(PARAM *param,uint index,SEL_ARG *key_tree, 
+                                  bool update_tbl_stats);
 static ha_rows check_quick_keys(PARAM *param,uint index,SEL_ARG *key_tree,
 				char *min_key,uint min_key_flag,
 				char *max_key, uint max_key_flag);
@@ -3231,7 +3232,8 @@
       bool read_index_only= index_read_must_be_used ? TRUE :
                             (bool) param->table->used_keys.is_set(keynr);
 
-      found_records= check_quick_select(param, idx, *key);
+      found_records= check_quick_select(param, idx, *key, 
+                                        !index_read_must_be_used);
       if (param->is_ror_scan)
       {
         tree->n_ror_scans++;
@@ -5150,10 +5152,13 @@
   scan on given index using given SEL_ARG intervals tree.
   SYNOPSIS
     check_quick_select
-      param  Parameter from test_quick_select
-      idx    Number of index to use in PARAM::key SEL_TREE::key
-      tree   Transformed selection condition, tree->key[idx] holds intervals
-             tree to be used for scanning.
+      param             Parameter from test_quick_select
+      idx               Number of index to use in tree->keys
+      tree              Transformed selection condition, tree->keys[idx]
+                        holds the range tree to be used for scanning.
+      update_tbl_stats  If true, update table->quick_keys with information
+                        about range scan we've evaluated.
+
   NOTES
     param->is_ror_scan is set to reflect if the key scan is a ROR (see
     is_key_scan_ror function for more info)
@@ -5167,7 +5172,7 @@
 */
 
 static ha_rows
-check_quick_select(PARAM *param,uint idx,SEL_ARG *tree)
+check_quick_select(PARAM *param,uint idx,SEL_ARG *tree, bool update_tbl_stats)
 {
   ha_rows records;
   bool    cpk_scan;
@@ -5207,9 +5212,16 @@
   records=check_quick_keys(param,idx,tree,param->min_key,0,param->max_key,0);
   if (records != HA_POS_ERROR)
   {
-    param->table->quick_keys.set_bit(key);
+    if (update_tbl_stats)
+    {
+      param->table->quick_keys.set_bit(key);
+      param->table->quick_key_parts[key]=param->max_key_part+1;
+    }
+    /*
+      Need to save quick_rows in any case as it is used when calculating
+      cost of ROR intersection:
+    */
     param->table->quick_rows[key]=records;
-    param->table->quick_key_parts[key]=param->max_key_part+1;
 
     if (cpk_scan)
       param->is_ror_scan= TRUE;
@@ -7301,7 +7313,7 @@
                                            &cur_param_idx);
       /* Check if this range tree can be used for prefix retrieval. */
       cur_quick_prefix_records= check_quick_select(param, cur_param_idx,
-                                                    cur_index_tree);
+                                                    cur_index_tree, TRUE);
     }
     cost_group_min_max(table, cur_index_info, used_key_parts,
                        cur_group_key_parts, tree, cur_index_tree,

--- 1.119/sql/table.h	2005-11-03 16:21:19 +03:00
+++ 1.120/sql/table.h	2005-11-24 12:54:40 +03:00
@@ -216,9 +216,15 @@
   uchar		*null_flags;
   query_id_t	query_id;
 
+  /* 
+    For each key that has quick_keys.is_set(key) == TRUE: estimate of #records
+    and max #key parts that range access would use.
+  */
   ha_rows	quick_rows[MAX_KEY];
-  key_part_map  const_key_parts[MAX_KEY];
   uint		quick_key_parts[MAX_KEY];
+  
+  /* Bitmaps of key parts that =const for the entire join. */
+  key_part_map  const_key_parts[MAX_KEY];
 
   /*
     If this table has TIMESTAMP field with auto-set property (pointed by