Bug#50402 Optimizer producing wrong results when using Index Merge on InnoDB

Subselect executes twice, at JOIN::optimize stage
and at JOIN::execute stage. At optimize stage
Innodb prebuilt struct which is used for the
retrieval of column values is initialized in.
ha_innobase::index_read(), prebuilt->sql_stat_start is true.
After QUICK_ROR_INTERSECT_SELECT finished his job it
restores read_set/write_set bitmaps with initial values
and deactivates one of the handlers used by
QUICK_ROR_INTERSECT_SELECT in JOIN::cleanup
(it's the case when we reuse original handler as one of
 handlers required by QUICK_ROR_INTERSECT_SELECT object).
On second subselect execution inactive handler is activated
in  QUICK_RANGE_SELECT::reset, file->ha_index_init().
In ha_index_init Innodb prebuilt struct is reinitialized
with inappropriate read_set/write_set bitmaps. Further
reinitialization in ha_innobase::index_read() does not
happen as prebuilt->sql_stat_start is false.
It leads to partial retrieval of required field values
and we get a mix of field values from different records
in the record buffer.
The fix is to reset
read_set/write_set bitmaps as these values
are required for proper intialization of
internal InnoDB struct which is used for
the retrieval of column values
(see build_template(), ha_innodb.cc)

1 files changed, 8 insertions, 3 deletions

diff --git a/sql/opt_range.cc b/sql/opt_range.cc
index eae79e63c19..d4a2bc3b138 100644
--- a/sql/opt_range.cc
+++ b/sql/opt_range.cc
@@ -8451,9 +8451,14 @@ int QUICK_RANGE_SELECT::reset()
   in_range= FALSE;
   cur_range= (QUICK_RANGE**) ranges.buffer;
 
-  if (file->inited == handler::NONE && (error= file->ha_index_init(index,1)))
-    DBUG_RETURN(error);
- 
+  if (file->inited == handler::NONE)
+  {
+    if (in_ror_merged_scan)
+      head->column_bitmaps_set_no_signal(&column_bitmap, &column_bitmap);
+    if ((error= file->ha_index_init(index,1)))
+        DBUG_RETURN(error);
+  }
+
   /* Do not allocate the buffers twice. */
   if (multi_range_length)
   {