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5.0 repository of hf. When hf does a push these changes will
be propagated to the main repository and, within 24 hours after the
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ChangeSet@stripped, 2008-02-15 22:58:56+04:00, holyfoot@stripped +3 -0
Bug #32942 now() - interval '7200' second NOT pre-calculated, causing "full table scan"
Problem is not about intervals and doesn't actually cause 'full table scan'.
We have an optimization for DISTINCT when we have
'DISTINCT field_from_first_join_table' we don't need to read all the
rows from the JOIN-ed table if we found one conforming row.
It stopped working in 5.0 as we return NESTED_LOOP_OK if we came upon
that case in the evaluate_join_record() and that doesn't break the
recordreading loop in sub_select().
Fixed by returning NESTED_LOOP_NO_MORE_ROWS in this case.
mysql-test/r/select.result@stripped, 2008-02-15 22:58:55+04:00, holyfoot@stripped +15 -0
Bug #32942 now() - interval '7200' second is NOT pre-calculated, causing "full table scan".
test result
mysql-test/t/select.test@stripped, 2008-02-15 22:58:55+04:00, holyfoot@stripped +18 -0
Bug #32942 now() - interval '7200' second is NOT pre-calculated, causing "full table scan"
test case
sql/sql_select.cc@stripped, 2008-02-15 22:58:55+04:00, holyfoot@stripped +1 -1
Bug #32942 now() - interval '7200' second NOT pre-calculated, causing "full table scan"
return NESTED_LOOP_NO_MORE_ROWS when we don't need to read rows from
this table anymore
diff -Nrup a/mysql-test/r/select.result b/mysql-test/r/select.result
--- a/mysql-test/r/select.result 2007-11-18 00:01:31 +04:00
+++ b/mysql-test/r/select.result 2008-02-15 22:58:55 +04:00
@@ -4328,4 +4328,19 @@ SELECT * FROM t1 WHERE c1 > NULL + 1;
c1
DROP TABLE t1;
+CREATE TABLE t1 (a INT, b INT);
+CREATE TABLE t2 (a INT, c INT, KEY(a));
+INSERT INTO t1 VALUES (1, 1), (2, 2);
+INSERT INTO t2 VALUES (1, 1), (1, 2), (1, 3), (1, 4), (1, 5),
+(2, 1), (2, 2), (2, 3), (2, 4), (2, 5),
+(3, 1), (3, 2), (3, 3), (3, 4), (3, 5),
+(4, 1), (4, 2), (4, 3), (4, 4), (4, 5);
+FLUSH STATUS;
+SELECT DISTINCT b FROM t1 LEFT JOIN t2 USING(a) WHERE c <= 3;
+b
+1
+2
+SHOW STATUS LIKE 'Handler_read*';
+Variable_name Value
+DROP TABLE t1, t2;
End of 5.0 tests
diff -Nrup a/mysql-test/t/select.test b/mysql-test/t/select.test
--- a/mysql-test/t/select.test 2007-11-18 00:01:30 +04:00
+++ b/mysql-test/t/select.test 2008-02-15 22:58:55 +04:00
@@ -3672,4 +3672,22 @@ DROP TABLE t1;
--echo
+#
+# Bug #32942 now() - interval '7200' second is NOT pre-calculated, causing "full table scan"
+#
+
+CREATE TABLE t1 (a INT, b INT);
+CREATE TABLE t2 (a INT, c INT, KEY(a));
+
+INSERT INTO t1 VALUES (1, 1), (2, 2);
+INSERT INTO t2 VALUES (1, 1), (1, 2), (1, 3), (1, 4), (1, 5),
+ (2, 1), (2, 2), (2, 3), (2, 4), (2, 5),
+ (3, 1), (3, 2), (3, 3), (3, 4), (3, 5),
+ (4, 1), (4, 2), (4, 3), (4, 4), (4, 5);
+
+FLUSH STATUS;
+SELECT DISTINCT b FROM t1 LEFT JOIN t2 USING(a) WHERE c <= 3;
+SHOW STATUS LIKE 'Handler_read*';
+DROP TABLE t1, t2;
+
--echo End of 5.0 tests
diff -Nrup a/sql/sql_select.cc b/sql/sql_select.cc
--- a/sql/sql_select.cc 2007-12-13 14:49:12 +04:00
+++ b/sql/sql_select.cc 2008-02-15 22:58:55 +04:00
@@ -10791,7 +10791,7 @@ evaluate_join_record(JOIN *join, JOIN_TA
we found a row, as no new rows can be added to the result.
*/
if (not_used_in_distinct && found_records != join->found_records)
- return NESTED_LOOP_OK;
+ return NESTED_LOOP_NO_MORE_ROWS;
}
else
join_tab->read_record.file->unlock_row();
