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LEFT JOIN optimization: Change LEFT JOIN to normal join if possible

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mysql-test/r/select.result:
  Added test for LEFT JOIN optimization
mysql-test/t/select.test:
  Added test for LEFT JOIN optimization
sql/item.h:
  LEFT JOIN optimization
sql/item_cmpfunc.cc:
  LEFT JOIN optimization
sql/item_cmpfunc.h:
  LEFT JOIN optimization
sql/item_func.cc:
  LEFT JOIN optimization
sql/item_func.h:
  LEFT JOIN optimization
sql/item_strfunc.cc:
  LEFT JOIN optimization
sql/sql_base.cc:
  Heart of LEFT JOIN optimization
This commit is contained in:
unknown
2003-06-26 05:38:19 +03:00
parent 3d5f6a8867
commit a3beaaa3af
9 changed files with 147 additions and 33 deletions
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16
sql/sql_base.cc
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@ -1903,11 +1903,11 @@ bool setup_tables(TABLE_LIST *tables)
table->used_fields=0;
table->const_table=0;
table->outer_join=table->null_row=0;
table->null_row=0;
table->status=STATUS_NO_RECORD;
table->keys_in_use_for_query= table->keys_in_use;
table->used_keys= table->keys_for_keyread;
table->maybe_null=test(table->outer_join=table_list->outer_join);
table->maybe_null=test(table->outer_join= table_list->outer_join);
table->tablenr=tablenr;
table->map= (table_map) 1 << tablenr;
table->force_index= table_list->force_index;
@ -2027,6 +2027,7 @@ insert_fields(THD *thd,TABLE_LIST *tables, const char *db_name,
int setup_conds(THD *thd,TABLE_LIST *tables,COND **conds)
{
table_map not_null_tables= 0;
DBUG_ENTER("setup_conds");
thd->set_query_id=1;
thd->cond_count=0;
@ -2036,6 +2037,7 @@ int setup_conds(THD *thd,TABLE_LIST *tables,COND **conds)
thd->where="where clause";
if ((*conds)->fix_fields(thd,tables))
DBUG_RETURN(1);
not_null_tables= (*conds)->not_null_tables();
}
/* Check if we are using outer joins */
@ -2049,9 +2051,15 @@ int setup_conds(THD *thd,TABLE_LIST *tables,COND **conds)
DBUG_RETURN(1);
thd->cond_count++;
/* If it's a normal join, add the ON/USING expression to the WHERE */
if (!table->outer_join)
/*
If it's a normal join or a LEFT JOIN which can be optimized away
add the ON/USING expression to the WHERE
*/
if (!table->outer_join ||
((table->table->map & not_null_tables) &&
!(specialflag & SPECIAL_NO_NEW_FUNC)))
{
table->outer_join= 0;
if (!(*conds=and_conds(*conds, table->on_expr)))
DBUG_RETURN(1);
table->on_expr=0;