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Bug #48475: DISTINCT is ignored with GROUP BY WITH ROLLUP and

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only const tables

The problem was caused by two shortcuts in the optimizer that
are inapplicable in the ROLLUP case.

Normally in a case when only const tables are involved in a
query, DISTINCT clause can be safely optimized away since there
may be only one row produced by the join. Similarly, we don't
need to create a temporary table to resolve DISTINCT/GROUP
BY/ORDER BY. Both of these are inapplicable when the WITH
ROLLUP modifier is present.

Fixed by disabling the said optimizations for the WITH ROLLUP
case.

mysql-test/r/olap.result:
  Added a test case for bug #48475.
mysql-test/t/olap.test:
  Added a test case for bug #48475.
sql/sql_select.cc:
  Disabled const-only table optimizations for the WITH ROLLUP
  case.
This commit is contained in:
Alexey Kopytov 2009-11-06 09:44:01 +03:00
parent 43358bccd1
commit 39f9a3ffd0
3 changed files with 41 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
mysql-test/r/olap.result
View File

@ -753,4 +753,16 @@ b
100 100
NULL NULL
DROP TABLE t1, t2; DROP TABLE t1, t2;
#
# Bug #48475: DISTINCT is ignored with GROUP BY WITH ROLLUP
# and only const tables
CREATE TABLE t1 (a INT);
CREATE TABLE t2 (b INT);
INSERT INTO t1 VALUES (1);
INSERT INTO t2 VALUES (1);
SELECT DISTINCT b FROM t1, t2 GROUP BY a, b WITH ROLLUP;
b
1
NULL
DROP TABLE t1, t2;
End of 5.0 tests End of 5.0 tests

13
mysql-test/t/olap.test
View File

@ -390,4 +390,17 @@ SELECT DISTINCT b FROM t1, t2 GROUP BY a, b WITH ROLLUP;
DROP TABLE t1, t2; DROP TABLE t1, t2;
--echo #
--echo # Bug #48475: DISTINCT is ignored with GROUP BY WITH ROLLUP
--echo # and only const tables
CREATE TABLE t1 (a INT);
CREATE TABLE t2 (b INT);
INSERT INTO t1 VALUES (1);
INSERT INTO t2 VALUES (1);
SELECT DISTINCT b FROM t1, t2 GROUP BY a, b WITH ROLLUP;
DROP TABLE t1, t2;
--echo End of 5.0 tests --echo End of 5.0 tests

23
sql/sql_select.cc
View File

@ -929,14 +929,20 @@ JOIN::optimize()
DBUG_RETURN(1); DBUG_RETURN(1);
} }
if (select_lex->olap == ROLLUP_TYPE && rollup_process_const_fields()) if (rollup.state != ROLLUP::STATE_NONE)
{ {
DBUG_PRINT("error", ("Error: rollup_process_fields() failed")); if (rollup_process_const_fields())
DBUG_RETURN(1); {
DBUG_PRINT("error", ("Error: rollup_process_fields() failed"));
DBUG_RETURN(1);
}
}
else
{
/* Remove distinct if only const tables */
select_distinct= select_distinct && (const_tables != tables);
} }
/* Remove distinct if only const tables */
select_distinct= select_distinct && (const_tables != tables);
thd_proc_info(thd, "preparing"); thd_proc_info(thd, "preparing");
if (result->initialize_tables(this)) if (result->initialize_tables(this))
{ {
@ -1216,11 +1222,14 @@ JOIN::optimize()
- We are using an ORDER BY or GROUP BY on fields not in the first table - We are using an ORDER BY or GROUP BY on fields not in the first table
- We are using different ORDER BY and GROUP BY orders - We are using different ORDER BY and GROUP BY orders
- The user wants us to buffer the result. - The user wants us to buffer the result.
When the WITH ROLLUP modifier is present, we cannot skip temporary table
creation for the DISTINCT clause just because there are only const tables.
*/ */
need_tmp= (const_tables != tables && need_tmp= ((const_tables != tables &&
((select_distinct || !simple_order || !simple_group) || ((select_distinct || !simple_order || !simple_group) ||
(group_list && order) || (group_list && order) ||
test(select_options & OPTION_BUFFER_RESULT))); test(select_options & OPTION_BUFFER_RESULT))) ||
rollup.state != ROLLUP::STATE_NONE && select_distinct);
// No cache for MATCH // No cache for MATCH
make_join_readinfo(this, make_join_readinfo(this,