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MWL#17: Table elimination

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- Fix print_join() to work both for EXPLAIN EXTENDED (after table elimination) and for 
  CREATE VIEW (after join->prepare() but without any optimization).

mysql-test/r/union.result:
  MWL#17: Table elimination
  - Adjust test results
This commit is contained in:
Sergey Petrunia 2009-06-15 00:59:24 +04:00
parent b1e25edc9b
commit 6b4727dcb9
2 changed files with 17 additions and 7 deletions
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2
mysql-test/r/union.result
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@ -522,7 +522,7 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
2 UNION t2 const PRIMARY PRIMARY 4 const 1 100.00
NULL UNION RESULT <union1,2> ALL NULL NULL NULL NULL NULL NULL
Warnings:
Note 1003 (select '1' AS `a`,'1' AS `b` from `test`.`t1` where ('1' = 1)) union (select '1' AS `a`,'10' AS `b` from `test`.`t2` where ('1' = 1))
Note 1003 (select '1' AS `a`,'1' AS `b` from `test`.`t1` where 1) union (select '1' AS `a`,'10' AS `b` from `test`.`t2` where 1)
(select * from t1 where a=5) union (select * from t2 where a=1);
a b
1 10

22
sql/sql_select.cc
View File

@ -16937,18 +16937,28 @@ static void print_join(THD *thd,
*t= ti++;
DBUG_ASSERT(tables->elements >= 1);
//pserey:TODO check!
/*
Assert that the first table in the list isn't eliminated (if it was we
would have skipped the entire join nest)
*/
DBUG_ASSERT(!eliminated_tables ||
!((*table)->table && ((*table)->table->map & eliminated_tables) ||
(*table)->nested_join && !((*table)->nested_join->used_tables &
~eliminated_tables)));
(*table)->print(thd, eliminated_tables, str, query_type);
TABLE_LIST **end= table + tables->elements;
for (TABLE_LIST **tbl= table + 1; tbl < end; tbl++)
{
TABLE_LIST *curr= *tbl;
// psergey-todo-todo:
// base table: check
if (curr->table && (curr->table->map & eliminated_tables) ||
curr->nested_join && !(curr->nested_join->used_tables &
~eliminated_tables))
/*
The (*) check guards againist the case of printing the query for
CREATE VIEW. There we'll have nested_join->used_tables==0.
*/
if (eliminated_tables && // (*)
(curr->table && (curr->table->map & eliminated_tables) ||
curr->nested_join && !(curr->nested_join->used_tables &
~eliminated_tables)))
{
continue;
}