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:
  Bug #32942 now() - interval '7200' second is NOT pre-calculated, causing "full table scan".
  
  test result
mysql-test/t/select.test:
  Bug #32942 now() - interval '7200' second is NOT pre-calculated, causing "full table scan"
  
  test case
sql/sql_select.cc:
  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

1 files changed, 18 insertions, 0 deletions

diff --git a/mysql-test/t/select.test b/mysql-test/t/select.test
index c48f2771aa8..51e0aeace7c 100644
--- a/mysql-test/t/select.test
+++ b/mysql-test/t/select.test
@@ -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