MWL#17: Table elimination: last fixes

- Add an @@optimizer_switch flag for table_elimination for debug build
- Better comments 

mysql-test/t/index_merge_myisam.test:
  MWL#17: Table elimination: last fixes
  - Add an @@optimizer_switch flag for table_elimination for debug build
sql/mysql_priv.h:
  MWL#17: Table elimination: last fixes
  - Add an @@optimizer_switch flag for table_elimination for debug build
sql/mysqld.cc:
  MWL#17: Table elimination: last fixes
  - Add an @@optimizer_switch flag for table_elimination for debug build

mysql-test/t/index_merge_myisam.test

@@ -25,15 +25,19 @@ let $merge_table_support= 1;
 --echo #  we get another @@optimizer_switch user)
 --echo #
 
+--replace_regex /,table_elimination=on//
 select @@optimizer_switch;
 
 set optimizer_switch='index_merge=off,index_merge_union=off';
+--replace_regex /,table_elimination=on//
 select @@optimizer_switch;
 
 set optimizer_switch='index_merge_union=on';
+--replace_regex /,table_elimination=on//
 select @@optimizer_switch;
 
 set optimizer_switch='default,index_merge_sort_union=off';
+--replace_regex /,table_elimination=on//
 select @@optimizer_switch;
 
 --error ER_WRONG_VALUE_FOR_VAR
@@ -71,17 +75,21 @@ set optimizer_switch='default,index_merge=on,index_merge=off,default';
 
 set optimizer_switch=default;
 set optimizer_switch='index_merge=off,index_merge_union=off,default';
+--replace_regex /,table_elimination=on//
 select @@optimizer_switch;
 set optimizer_switch=default;
 
 # Check setting defaults for global vars
+--replace_regex /,table_elimination=on//
 select @@global.optimizer_switch;
 set @@global.optimizer_switch=default;
+--replace_regex /,table_elimination=on//
 select @@global.optimizer_switch;
 
 --echo #
 --echo # Check index_merge's @@optimizer_switch flags
 --echo #
+--replace_regex /,table_elimination.on//
 select @@optimizer_switch;
 
 create table t0 (a int);
@@ -182,6 +190,7 @@ set optimizer_switch='default,index_merge_union=off';
 explain select * from t1 where a=10 and b=10 or c=10;
 
 set optimizer_switch=default;
+--replace_regex /,table_elimination.on//
 show variables like 'optimizer_switch';
 
 drop table t0, t1;

sql/mysql_priv.h

@@ -528,14 +528,27 @@ protected:
 #define OPTIMIZER_SWITCH_INDEX_MERGE_UNION 2
 #define OPTIMIZER_SWITCH_INDEX_MERGE_SORT_UNION 4
 #define OPTIMIZER_SWITCH_INDEX_MERGE_INTERSECT 8
-#define OPTIMIZER_SWITCH_LAST 16
 
+#ifdef DBUG_OFF
+#  define OPTIMIZER_SWITCH_LAST 16
+#else
+#  define OPTIMIZER_SWITCH_TABLE_ELIMINATION 16
+#  define OPTIMIZER_SWITCH_LAST 32
+#endif
+
+#ifdef DBUG_OFF 
 /* The following must be kept in sync with optimizer_switch_str in mysqld.cc */
-#define OPTIMIZER_SWITCH_DEFAULT (OPTIMIZER_SWITCH_INDEX_MERGE | \
+#  define OPTIMIZER_SWITCH_DEFAULT (OPTIMIZER_SWITCH_INDEX_MERGE | \
                                     OPTIMIZER_SWITCH_INDEX_MERGE_UNION | \
                                     OPTIMIZER_SWITCH_INDEX_MERGE_SORT_UNION | \
                                     OPTIMIZER_SWITCH_INDEX_MERGE_INTERSECT)
-
+#else 
+#  define OPTIMIZER_SWITCH_DEFAULT (OPTIMIZER_SWITCH_INDEX_MERGE | \
+                                    OPTIMIZER_SWITCH_INDEX_MERGE_UNION | \
+                                    OPTIMIZER_SWITCH_INDEX_MERGE_SORT_UNION | \
+                                    OPTIMIZER_SWITCH_INDEX_MERGE_INTERSECT | \
+                                    OPTIMIZER_SWITCH_TABLE_ELIMINATION)
+#endif
 
 /*
   Replication uses 8 bytes to store SQL_MODE in the binary log. The day you

sql/mysqld.cc

@@ -298,8 +298,13 @@ TYPELIB sql_mode_typelib= { array_elements(sql_mode_names)-1,"",
 static const char *optimizer_switch_names[]=
 {
   "index_merge","index_merge_union","index_merge_sort_union",
-  "index_merge_intersection", "default", NullS
+  "index_merge_intersection",
+#ifndef DBUG_OFF
+  "table_elimination",
+#endif
+  "default", NullS
 };
+
 /* Corresponding defines are named OPTIMIZER_SWITCH_XXX */
 static const unsigned int optimizer_switch_names_len[]=
 {
@@ -307,6 +312,9 @@ static const unsigned int optimizer_switch_names_len[]=
   sizeof("index_merge_union") - 1,
   sizeof("index_merge_sort_union") - 1,
   sizeof("index_merge_intersection") - 1,
+#ifndef DBUG_OFF
+  sizeof("table_elimination") - 1,
+#endif
   sizeof("default") - 1
 };
 TYPELIB optimizer_switch_typelib= { array_elements(optimizer_switch_names)-1,"",
@@ -382,7 +390,10 @@ static const char *sql_mode_str= "OFF";
 /* Text representation for OPTIMIZER_SWITCH_DEFAULT */
 static const char *optimizer_switch_str="index_merge=on,index_merge_union=on,"
                                         "index_merge_sort_union=on,"
-                                        "index_merge_intersection=on";
+                                        "index_merge_intersection=on"
+#ifndef DBUG_OFF                                        
+                                        ",table_elimination=on";
+#endif
 static char *mysqld_user, *mysqld_chroot, *log_error_file_ptr;
 static char *opt_init_slave, *language_ptr, *opt_init_connect;
 static char *default_character_set_name;
@@ -6929,8 +6940,11 @@ The minimum value for this variable is 4096.",
    0, GET_ULONG, OPT_ARG, MAX_TABLES+1, 0, MAX_TABLES+2, 0, 1, 0},
   {"optimizer_switch", OPT_OPTIMIZER_SWITCH,
    "optimizer_switch=option=val[,option=val...], where option={index_merge, "
-   "index_merge_union, index_merge_sort_union, index_merge_intersection} and "
-   "val={on, off, default}.",
+   "index_merge_union, index_merge_sort_union, index_merge_intersection"
+#ifndef DBUG_OFF
+   ", table_elimination"
+#endif 
+   "} and val={on, off, default}.",
    (uchar**) &optimizer_switch_str, (uchar**) &optimizer_switch_str, 0, GET_STR, REQUIRED_ARG, 
    /*OPTIMIZER_SWITCH_DEFAULT*/0,
    0, 0, 0, 0, 0},