MDEV-5675 - Performance: my_hash_sort_bin is called too often

Reduced number of my_hash_sort_bin() calls from 4 to 1 per query.
Reduced number of memory accesses done by my_hash_sort_bin().

Details:
- let MDL subsystem use pre-calculated hash value for hash
  inserts and deletes
- let table cache use pre-calculated MDL hash value
- MDL namespace is excluded from hash value calculation, so that
  hash value can be used by table cache as is
- hash value for MDL is calculated as resulting hash value + MDL
  namespace
- extended hash implementation to accept user defined hash function

1 files changed, 3 insertions, 1 deletions

diff --git a/sql/sql_base.cc b/sql/sql_base.cc
index 8cfb7850ae3..82f98e0604b 100644
--- a/sql/sql_base.cc
+++ b/sql/sql_base.cc
@@ -2296,7 +2296,9 @@ bool open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT *mem_root,
 retry_share:
 
   share= tdc_acquire_share(thd, table_list->db, table_list->table_name,
-                           key, key_length, gts_flags, &table);
+                           key, key_length,
+                           table_list->mdl_request.key.tc_hash_value(),
+                           gts_flags, &table);
 
   if (!share)
   {