MDEV-6878: Use of uninitialized saved_primary_key in Mrr_ordered_index_reader::resume_read()

- Make Mrr_ordered_index_reader::resume_read() restore index position 
  only if it was saved before with Mrr_ordered_index_reader::interrupt_read().

1 files changed, 14 insertions, 9 deletions

diff --git a/sql/multi_range_read.cc b/sql/multi_range_read.cc
index b63db9ecea2..4665957528f 100644
--- a/sql/multi_range_read.cc
+++ b/sql/multi_range_read.cc
@@ -426,6 +426,7 @@ bool Mrr_ordered_index_reader::set_interruption_temp_buffer(uint rowid_length,
   *space_start += key_len;
 
   have_saved_rowid= FALSE;
+  read_was_interrupted= FALSE;
   return FALSE;
 }
 
@@ -434,6 +435,7 @@ void Mrr_ordered_index_reader::set_no_interruption_temp_buffer()
   support_scan_interruptions= FALSE;
   saved_key_tuple= saved_rowid= saved_primary_key= NULL; /* safety */
   have_saved_rowid= FALSE;
+  read_was_interrupted= FALSE;
 }
 
 void Mrr_ordered_index_reader::interrupt_read()
@@ -451,6 +453,7 @@ void Mrr_ordered_index_reader::interrupt_read()
              &table->key_info[table->s->primary_key],
              table->key_info[table->s->primary_key].key_length);
   }
+  read_was_interrupted= TRUE;
 
   /* Save the last rowid */
   memcpy(saved_rowid, file->ref, file->ref_length);
@@ -468,14 +471,17 @@ void Mrr_ordered_index_reader::position()
 void Mrr_ordered_index_reader::resume_read()
 {
   TABLE *table= file->get_table();
-  KEY *used_index= &table->key_info[file->active_index];
-  key_restore(table->record[0], saved_key_tuple, 
-              used_index, used_index->key_length);
-  if (saved_primary_key)
+  if (read_was_interrupted)
   {
-    key_restore(table->record[0], saved_primary_key, 
-                &table->key_info[table->s->primary_key],
-                table->key_info[table->s->primary_key].key_length);
+    KEY *used_index= &table->key_info[file->active_index];
+    key_restore(table->record[0], saved_key_tuple, 
+                used_index, used_index->key_length);
+    if (saved_primary_key)
+    {
+      key_restore(table->record[0], saved_primary_key, 
+                  &table->key_info[table->s->primary_key],
+                  table->key_info[table->s->primary_key].key_length);
+    }
   }
 }
 
@@ -557,8 +563,7 @@ int Mrr_ordered_index_reader::init(handler *h_arg, RANGE_SEQ_IF *seq_funcs,
   is_mrr_assoc= !MY_TEST(mode & HA_MRR_NO_ASSOCIATION);
   mrr_funcs= *seq_funcs;
   source_exhausted= FALSE;
-  if (support_scan_interruptions)
-    bzero(saved_key_tuple, key_info->key_length);
+  read_was_interrupted= false;
   have_saved_rowid= FALSE;
   return 0;
 }