Removed TABLE->sort to make it possible to have multiple active calls to

filesort and init_read_record() for the same table.
This will simplify code for WINDOW FUNCTIONS (MDEV-6115)

- Filesort_info renamed to SORT_INFO and moved to filesort.h
- filesort now returns SORT_INFO
- init_read_record() now takes a SORT_INFO parameter.
- unique declaration is moved to uniques.h
- subselect caching of buffers is now more explicit than before
- filesort_buffer is now reusable even if rec_length has changed.
- filsort_free_buffers() and free_io_cache() calls are removed
- Remove one malloc() when using get_addon_fields()

Other things:
- Added --debug-assert-on-not-freed-memory option to make it easier to
  debug some not-freed-memory issues.

1 files changed, 3 insertions, 0 deletions

diff --git a/sql/item_subselect.h b/sql/item_subselect.h
index 1b450044954..58b5a948048 100644
--- a/sql/item_subselect.h
+++ b/sql/item_subselect.h
@@ -95,6 +95,9 @@ public:
   subselect_engine *engine;
   /* unit of subquery */
   st_select_lex_unit *unit;
+  /* Cached buffers used when calling filesort in sub queries */
+  Filesort_buffer filesort_buffer;
+  LEX_STRING sortbuffer;
   /* A reference from inside subquery predicate to somewhere outside of it */
   class Ref_to_outside : public Sql_alloc
   {