BUG#40974: Incorrect query results when using clause evaluated using range check

- QUICK_INDEX_MERGE_SELECT deinitializes its rnd_pos() scan when it reaches EOF, but we 
  need to make the deinitialization in QUICK_INDEX_MERGE_SELECT destructor also. This is because
  certain execution strategies can stop scanning without reaching EOF, then then try to do a full
  table scan on this table. Failure to deinitialize caused the full scan to use (already empty) 
  table->sort and produce zero records.

mysql-test/r/index_merge.result:
  BUG#40974: Incorrect query results when using clause evaluated using range check
  - Testcase
mysql-test/t/index_merge.test:
  BUG#40974: Incorrect query results when using clause evaluated using range check
  - Testcase

1 files changed, 3 insertions, 0 deletions

diff --git a/sql/opt_range.cc b/sql/opt_range.cc
index 204ebdb6f33..744415fa2fe 100644
--- a/sql/opt_range.cc
+++ b/sql/opt_range.cc
@@ -1109,6 +1109,9 @@ QUICK_INDEX_MERGE_SELECT::~QUICK_INDEX_MERGE_SELECT()
     quick->file= NULL;
   quick_selects.delete_elements();
   delete pk_quick_select;
+  /* It's ok to call the next two even if they are already deinitialized */
+  end_read_record(&read_record);
+  free_io_cache(head);
   free_root(&alloc,MYF(0));
   DBUG_VOID_RETURN;
 }