MDEV-13115: Implement SELECT SKIP LOCKED

Adds an implementation for SELECT ... FOR UPDATE SKIP LOCKED /
SELECT ... LOCK IN SHARED MODE SKIP LOCKED

This is implemented only InnoDB at the moment, not in RockDB yet.

This adds a new hander flag HA_CAN_SKIP_LOCKED than
will be used when the storage engine advertises the flag.

When a storage engine indicates this flag it will get
TL_WRITE_SKIP_LOCKED and TL_READ_SKIP_LOCKED transaction types.

The Lex structure has been updated to store both the FOR UPDATE/LOCK IN
SHARE as well as the SKIP LOCKED so the SHOW CREATE VIEW
implementation is simplier.

"SELECT FOR UPDATE ... SKIP LOCKED" combined with CREATE TABLE AS or
INSERT.. SELECT on the result set is not safe for STATEMENT based
replication. MIXED replication will replicate this as row based events."

Thanks to guidance from Facebook commit
https://github.com/facebook/mysql-5.6/commit/193896c466d43fd905a62a60f1d73fd9c551a6e4
This helped verify basic test case, and components that need implementing
(even though every part was implemented differently).

Thanks Marko for guidance on simplier InnoDB implementation.

Reviewers: Marko, Monty

1 files changed, 5 insertions, 2 deletions

diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 4509b0a05ef..56a7ac6eb80 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -27939,11 +27939,14 @@ void st_select_lex::print(THD *thd, String *str, enum_query_type query_type)
   print_limit(thd, str, query_type);
 
   // lock type
-  if (lock_type == TL_READ_WITH_SHARED_LOCKS)
+  if (select_lock == select_lock_type::IN_SHARE_MODE)
     str->append(" lock in share mode");
-  else if (lock_type == TL_WRITE)
+  else if (select_lock == select_lock_type::FOR_UPDATE)
     str->append(" for update");
 
+  if (unlikely(skip_locked))
+    str->append(" skip locked");
+
   // PROCEDURE unsupported here
 }