Bug #53830: !table || (!table->read_set ||

             bitmap_is_set(table->read_set, field_index))

UPDATE on an InnoDB table modifying the same index that is used
to satisfy the WHERE condition could trigger a debug assertion
under some circumstances.

Since for engines with the HA_PRIMARY_KEY_IN_READ_INDEX flag
set results of an index scan on a secondary index are appended
by the primary key value, if a query involves only columns from
the primary key and a secondary index, the latter is considered
to be covering.

That tricks mysql_update() to mark for reading only columns
from the secondary index when it does an index scan to retrieve
rows to update in case a part of that key is also being
updated. However, there may be other columns in WHERE that are
part of the primary key, but not the secondary one.

What we actually want to do in this case is to add index
columns to the existing WHERE columns bitmap rather than
replace it.

3 files changed, 23 insertions, 1 deletions

diff --git a/sql/sql_update.cc b/sql/sql_update.cc
index 69f3a29e923..7df0898e841 100644
--- a/sql/sql_update.cc
+++ b/sql/sql_update.cc
@@ -397,7 +397,7 @@ int mysql_update(THD *thd,
       matching rows before updating the table!
     */
     if (used_index < MAX_KEY && old_covering_keys.is_set(used_index))
-      table->mark_columns_used_by_index(used_index);
+      table->add_read_columns_used_by_index(used_index);
     else
     {
       table->use_all_columns();
diff --git a/sql/table.cc b/sql/table.cc
index 8b97dd36170..0fef7fa639a 100644
--- a/sql/table.cc
+++ b/sql/table.cc
@@ -4378,6 +4378,27 @@ void st_table::mark_columns_used_by_index(uint index)
 
 
 /*
+  Add fields used by a specified index to the table's read_set.
+
+  NOTE:
+    The original state can be restored with
+    restore_column_maps_after_mark_index().
+*/
+
+void st_table::add_read_columns_used_by_index(uint index)
+{
+  MY_BITMAP *bitmap= &tmp_set;
+  DBUG_ENTER("st_table::add_read_columns_used_by_index");
+
+  set_keyread(TRUE);
+  bitmap_copy(bitmap, read_set);
+  mark_columns_used_by_index_no_reset(index, bitmap);
+  column_bitmaps_set(bitmap, write_set);
+  DBUG_VOID_RETURN;
+}
+
+
+/*
   Restore to use normal column maps after key read
 
   NOTES
diff --git a/sql/table.h b/sql/table.h
index bddb0731625..4125c252427 100644
--- a/sql/table.h
+++ b/sql/table.h
@@ -865,6 +865,7 @@ struct st_table {
   void prepare_for_position(void);
   void mark_columns_used_by_index_no_reset(uint index, MY_BITMAP *map);
   void mark_columns_used_by_index(uint index);
+  void add_read_columns_used_by_index(uint index);
   void restore_column_maps_after_mark_index();
   void mark_auto_increment_column(void);
   void mark_columns_needed_for_update(void);