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, 6 insertions, 2 deletions

diff --git a/sql/table_cache.h b/sql/table_cache.h
index a30a07b8357..6da6a667792 100644
--- a/sql/table_cache.h
+++ b/sql/table_cache.h
@@ -40,6 +40,7 @@ extern void tdc_unlock_share(TABLE_SHARE *share);
 extern TABLE_SHARE *tdc_acquire_share(THD *thd, const char *db,
                                       const char *table_name,
                                       const char *key, uint key_length,
+                                      my_hash_value_type hash_value,
                                       uint flags, TABLE **out_table);
 extern void tdc_release_share(TABLE_SHARE *share);
 extern bool tdc_remove_table(THD *thd, enum_tdc_remove_table_type remove_type,
@@ -88,7 +89,9 @@ static inline TABLE_SHARE *tdc_acquire_share(THD *thd, const char *db,
                                              const char *key,
                                              uint key_length, uint flags)
 {
-  return tdc_acquire_share(thd, db, table_name, key, key_length, flags, 0);
+  return tdc_acquire_share(thd, db, table_name, key, key_length,
+                           my_hash_sort(&my_charset_bin, (uchar*) key,
+                                        key_length), flags, 0);
 }
 
 
@@ -120,7 +123,8 @@ static inline TABLE_SHARE *tdc_acquire_share_shortlived(THD *thd, TABLE_LIST *tl
 {
   const char *key;
   uint        key_length= get_table_def_key(tl, &key);
-  return tdc_acquire_share(thd, tl->db, tl->table_name, key, key_length, flags);
+  return tdc_acquire_share(thd, tl->db, tl->table_name, key, key_length,
+                           tl->mdl_request.key.tc_hash_value(), flags, 0);
 }