Merge

mysql-test/r/optimizer_switch.result

@@ -4,19 +4,19 @@
 #
 select @@optimizer_switch;
 @@optimizer_switch
-index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on
+index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=on
 set optimizer_switch='index_merge=off,index_merge_union=off';
 select @@optimizer_switch;
 @@optimizer_switch
-index_merge=off,index_merge_union=off,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on
+index_merge=off,index_merge_union=off,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=on
 set optimizer_switch='index_merge_union=on';
 select @@optimizer_switch;
 @@optimizer_switch
-index_merge=off,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on
+index_merge=off,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=on
 set optimizer_switch='default,index_merge_sort_union=off';
 select @@optimizer_switch;
 @@optimizer_switch
-index_merge=on,index_merge_union=on,index_merge_sort_union=off,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on
+index_merge=on,index_merge_union=on,index_merge_sort_union=off,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=on
 set optimizer_switch=4;
 ERROR 42000: Variable 'optimizer_switch' can't be set to the value of '4'
 set optimizer_switch=NULL;
@@ -43,60 +43,60 @@ set optimizer_switch=default;
 set optimizer_switch='index_merge=off,index_merge_union=off,default';
 select @@optimizer_switch;
 @@optimizer_switch
-index_merge=off,index_merge_union=off,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on
+index_merge=off,index_merge_union=off,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=on
 set optimizer_switch=default;
 select @@global.optimizer_switch;
 @@global.optimizer_switch
-index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on
+index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=on
 set @@global.optimizer_switch=default;
 select @@global.optimizer_switch;
 @@global.optimizer_switch
-index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on
+index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=on
 #
 # Check index_merge's @@optimizer_switch flags
 #
 select @@optimizer_switch;
 @@optimizer_switch
-index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on
+index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=on
 
 BUG#37120 optimizer_switch allowable values not according to specification
 
 select @@optimizer_switch;
 @@optimizer_switch
-index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on
+index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=on
 set optimizer_switch='default,materialization=off';
 select @@optimizer_switch;
 @@optimizer_switch
-index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=off,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on
+index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=off,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=on
 set optimizer_switch='default,semijoin=off';
 select @@optimizer_switch;
 @@optimizer_switch
-index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=off,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on
+index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=off,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=on
 set optimizer_switch='default,loosescan=off';
 select @@optimizer_switch;
 @@optimizer_switch
-index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=off,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on
+index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=off,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=on
 set optimizer_switch='default,semijoin=off,materialization=off';
 select @@optimizer_switch;
 @@optimizer_switch
-index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=off,semijoin=off,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on
+index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=off,semijoin=off,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=on
 set optimizer_switch='default,materialization=off,semijoin=off';
 select @@optimizer_switch;
 @@optimizer_switch
-index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=off,semijoin=off,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on
+index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=off,semijoin=off,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=on
 set optimizer_switch='default,semijoin=off,materialization=off,loosescan=off';
 select @@optimizer_switch;
 @@optimizer_switch
-index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=off,materialization=off,semijoin=off,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on
+index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=off,materialization=off,semijoin=off,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=on
 set optimizer_switch='default,semijoin=off,loosescan=off';
 select @@optimizer_switch;
 @@optimizer_switch
-index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=off,materialization=on,semijoin=off,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on
+index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=off,materialization=on,semijoin=off,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=on
 set optimizer_switch='default,materialization=off,loosescan=off';
 select @@optimizer_switch;
 @@optimizer_switch
-index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=off,materialization=off,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on
+index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=off,materialization=off,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=on
 set optimizer_switch=default;
 select @@optimizer_switch;
 @@optimizer_switch
-index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on
+index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,firstmatch=on,loosescan=on,materialization=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr_sort_keys=on,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=on

sql/mysql_priv.h

@@ -580,11 +580,12 @@ class Default_object_creation_ctx : public Object_creation_ctx
 #define OPTIMIZER_SWITCH_JOIN_CACHE_INCREMENTAL (1<<16)
 #define OPTIMIZER_SWITCH_JOIN_CACHE_HASHED (1<<17)
 #define OPTIMIZER_SWITCH_JOIN_CACHE_BKA (1<<18)
+#define OPTIMIZER_SWITCH_OPTIMIZE_JOIN_BUFFER_SIZE (1<<19)
 #ifdef DBUG_OFF
-#  define OPTIMIZER_SWITCH_LAST (1<<19)
-#else
-#  define OPTIMIZER_SWITCH_TABLE_ELIMINATION (1<<19)
 #  define OPTIMIZER_SWITCH_LAST (1<<20)
+#else
+#  define OPTIMIZER_SWITCH_TABLE_ELIMINATION (1<<20)
+#  define OPTIMIZER_SWITCH_LAST (1<<21)
 #endif
 
 #ifdef DBUG_OFF 
@@ -605,7 +606,8 @@ class Default_object_creation_ctx : public Object_creation_ctx
                                     OPTIMIZER_SWITCH_SUBQUERY_CACHE | \
                                     OPTIMIZER_SWITCH_JOIN_CACHE_INCREMENTAL | \
                                     OPTIMIZER_SWITCH_JOIN_CACHE_HASHED | \
-                                    OPTIMIZER_SWITCH_JOIN_CACHE_BKA)
+                                    OPTIMIZER_SWITCH_JOIN_CACHE_BKA | \
+                                    OPTIMIZER_SWITCH_OPTIMIZE_JOIN_BUFFER_SIZE)
 #else
 #  define OPTIMIZER_SWITCH_DEFAULT (OPTIMIZER_SWITCH_INDEX_MERGE | \
                                     OPTIMIZER_SWITCH_INDEX_MERGE_UNION | \
@@ -623,7 +625,8 @@ class Default_object_creation_ctx : public Object_creation_ctx
                                     OPTIMIZER_SWITCH_MRR_SORT_KEYS|\
                                     OPTIMIZER_SWITCH_JOIN_CACHE_INCREMENTAL | \
                                     OPTIMIZER_SWITCH_JOIN_CACHE_HASHED | \
-                                    OPTIMIZER_SWITCH_JOIN_CACHE_BKA)
+                                    OPTIMIZER_SWITCH_JOIN_CACHE_BKA | \
+                                    OPTIMIZER_SWITCH_OPTIMIZE_JOIN_BUFFER_SIZE)
 #endif
 
 /*

sql/mysqld.cc

@@ -351,6 +351,7 @@ static const char *optimizer_switch_names[]=
   "join_cache_incremental",
   "join_cache_hashed",
   "join_cache_bka",
+  "optimize_join_buffer_size",
 #ifndef DBUG_OFF
   "table_elimination",
 #endif
@@ -379,6 +380,7 @@ static const unsigned int optimizer_switch_names_len[]=
   sizeof("join_cache_incremental") - 1,
   sizeof("join_cache_hashed") - 1,
   sizeof("join_cache_bka") - 1,
+  sizeof("optimize_join_buffer_size") - 1,
 #ifndef DBUG_OFF
   sizeof("table_elimination") - 1,
 #endif
@@ -482,7 +484,8 @@ static const char *optimizer_switch_str="index_merge=on,index_merge_union=on,"
                                         "mrr_sort_keys=on,"
                                         "join_cache_incremental=on,"
                                         "join_cache_hashed=on,"
-                                        "join_cache_bka=on"
+                                        "join_cache_bka=on,"
+                                        "optimize_join_buffer_size=on"
 #ifndef DBUG_OFF
                                         ",table_elimination=on";
 #else
@@ -7115,7 +7118,7 @@ thread is in the relay logs.",
    "The limit of the space for all join buffers used by a query.",
    &global_system_variables.join_buff_space_limit,
    &max_system_variables.join_buff_space_limit, 0, GET_ULL,
-   REQUIRED_ARG, 8*128*1024L, 2048+MALLOC_OVERHEAD, (longlong) ULONGLONG_MAX,
+   REQUIRED_ARG, 16*128*1024L, 2048+MALLOC_OVERHEAD, (longlong) ULONGLONG_MAX,
    MALLOC_OVERHEAD, 2048, 0},
    {"join_cache_level", OPT_JOIN_CACHE_LEVEL,
    "Controls what join operations can be executed with join buffers. Odd numbers are used for plain join buffers while even numbers are used for linked buffers",

sql/sql_join_cache.cc

@@ -747,6 +747,7 @@ ulong JOIN_CACHE::get_min_join_buffer_size()
     avg_aux_buffer_incr= add_sz/min_records;
     min_sz+= add_sz;
     min_sz+= pack_length_with_blob_ptrs;
+    set_if_bigger(min_sz, 1);
     min_buff_size= min_sz;
   }
   return min_buff_size;
@@ -759,16 +760,20 @@ ulong JOIN_CACHE::get_min_join_buffer_size()
   SYNOPSIS
     get_max_join_buffer_size()
 
+    optimize_buff_size  FALSE <-> do not take more memory than needed for
+                        the estimated number of records in the partial join 
+
   DESCRIPTION
     At the first its invocation for the cache the function calculates the
-    maximum possible size of join buffer for the cache. This value does not
-    exceed the estimate of the number of records 'max_records' in the partial
-    join that joins tables from the first one through join_tab. This value
-    is also capped off by the value of join_tab->join_buffer_size_limit, if it
-    has been set a to non-zero value, and by the value of the system parameter 
-    join_buffer_size - otherwise. After the calculation of the interesting size
-    the function saves the value in the field 'max_buff_size' in order to use
-    it directly at the next  invocations of the function.
+    maximum possible size of join buffer for the cache. If the parameter
+    optimize_buff_size true then this value does not exceed the size of the
+    space needed for the estimated number of records 'max_records' in the
+    partial join that joins tables from the first one through join_tab. This
+    value is also capped off by the value of join_tab->join_buffer_size_limit,
+    if it has been set a to non-zero value, and by the value of the system
+    parameter join_buffer_size - otherwise. After the calculation of the
+    interesting size the function saves the value in the field 'max_buff_size'
+    in order to use it directly at the next  invocations of the function.
 
   NOTES
     Currently the value of join_tab->join_buffer_size_limit is initialized
@@ -778,7 +783,7 @@ ulong JOIN_CACHE::get_min_join_buffer_size()
     The maximum possible size of the join buffer of this cache 
 */
 
-ulong JOIN_CACHE::get_max_join_buffer_size()
+ulong JOIN_CACHE::get_max_join_buffer_size(bool optimize_buff_size)
 {
   if (!max_buff_size)
   {
@@ -795,12 +800,17 @@ ulong JOIN_CACHE::get_max_join_buffer_size()
     ulong limit_sz= join->thd->variables.join_buff_size;
     if (join_tab->join_buffer_size_limit)
       set_if_smaller(limit_sz, join_tab->join_buffer_size_limit);
+    if (!optimize_buff_size)
+      max_sz= limit_sz;
+    else
+    {    
       if (limit_sz / max_records > space_per_record)
         max_sz= space_per_record * max_records;
       else
         max_sz= limit_sz;
       max_sz+= pack_length_with_blob_ptrs;
       set_if_smaller(max_sz, limit_sz);
+    }
     set_if_bigger(max_sz, min_sz);
     max_buff_size= max_sz;
   }
@@ -843,6 +853,8 @@ int JOIN_CACHE::alloc_buffer()
   ulonglong curr_min_buff_space_sz= 0;
   ulonglong join_buff_space_limit=
     join->thd->variables.join_buff_space_limit;
+  bool optimize_buff_size= 
+         optimizer_flag(join->thd, OPTIMIZER_SWITCH_OPTIMIZE_JOIN_BUFFER_SIZE);
   double partial_join_cardinality=  (join_tab-1)->get_partial_join_cardinality();
   buff= NULL;
   min_buff_size= 0;
@@ -852,7 +864,7 @@ int JOIN_CACHE::alloc_buffer()
                  (ulonglong) partial_join_cardinality : join_buff_space_limit;
   set_if_bigger(max_records, 10);
   min_buff_size= get_min_join_buffer_size();
-  buff_size= get_max_join_buffer_size();
+  buff_size= get_max_join_buffer_size(optimize_buff_size);
   for (tab= join->join_tab+join->const_tables; tab <= join_tab; tab++)
   {
     cache= tab->cache;
@@ -865,8 +877,9 @@ int JOIN_CACHE::alloc_buffer()
 
   if (curr_min_buff_space_sz > join_buff_space_limit ||
       (curr_buff_space_sz > join_buff_space_limit &&
+       (!optimize_buff_size || 
         join->shrink_join_buffers(join_tab, curr_buff_space_sz,
-                                 join_buff_space_limit)))
+                                  join_buff_space_limit))))
     goto fail;
                                
   for (ulong buff_size_decr= (buff_size-min_buff_size)/4 + 1; ; )

sql/sql_join_cache.h

@@ -583,7 +583,7 @@ class JOIN_CACHE :public Sql_alloc
   /* Get the minimum possible size of the cache join buffer */
   virtual ulong get_min_join_buffer_size();
   /* Get the maximum possible size of the cache join buffer */ 
-  virtual ulong get_max_join_buffer_size();
+  virtual ulong get_max_join_buffer_size(bool optimize_buff_size);
 
   /* Shrink the size if the cache join buffer in a given ratio */
   bool shrink_join_buffer_in_ratio(ulonglong n, ulonglong d);