MWL#163 lp:798213: Remove the --innodb-release-locks-early feature.

The bug lp:798213 exposes a design flaw in --innodb-release-locks-early.
It does not work with InnoDB crash recovery, so it breaks transactional
integrety. So remove the feature.

4 files changed, 1 insertions, 83 deletions

diff --git a/storage/xtradb/handler/ha_innodb.cc b/storage/xtradb/handler/ha_innodb.cc
index c4e6fa0df0d..f409b88cc7b 100644
--- a/storage/xtradb/handler/ha_innodb.cc
+++ b/storage/xtradb/handler/ha_innodb.cc
@@ -248,7 +248,6 @@ static const char* innobase_change_buffering_values[IBUF_USE_COUNT] = {
 static INNOBASE_SHARE *get_share(const char *table_name);
 static void free_share(INNOBASE_SHARE *share);
 static int innobase_close_connection(handlerton *hton, THD* thd);
-static void innobase_prepare_ordered(handlerton *hton, THD* thd, bool all);
 static void innobase_commit_ordered(handlerton *hton, THD* thd, bool all);
 static int innobase_commit(handlerton *hton, THD* thd, bool all);
 static int innobase_rollback(handlerton *hton, THD* thd, bool all);
@@ -2084,10 +2083,6 @@ innobase_init(
         innobase_hton->savepoint_set=innobase_savepoint;
         innobase_hton->savepoint_rollback=innobase_rollback_to_savepoint;
         innobase_hton->savepoint_release=innobase_release_savepoint;
-	if (innobase_release_locks_early)
-		innobase_hton->prepare_ordered=innobase_prepare_ordered;
-	else
-		innobase_hton->prepare_ordered=NULL;
         innobase_hton->commit_ordered=innobase_commit_ordered;
         innobase_hton->commit=innobase_commit;
         innobase_hton->rollback=innobase_rollback;
@@ -2801,54 +2796,6 @@ innobase_start_trx_and_assign_read_view(
 	DBUG_RETURN(0);
 }
 
-/*****************************************************************//**
-Release row locks early during prepare phase.
-
-Only enabled if --innodb-release-locks-early=1. In this case, a prepared
-transaction is treated as committed to memory (but not to disk), and we
-release row locks at the end of the prepare phase.
-
-The consistent commit ordering guarantees of prepare_ordered() calls means
-that transactions will not be binlogged in different order than locks are
-released (which would cause trouble for statement-based replication).
-
-This optimisation is not 100% safe, so is not enabled by default. But some
-applications may decide to enable it to reduce contention on hotspot rows.
-
-The consequences of enabling this are:
-
- - It is not possible to rollback after successful prepare(). If there is
-   a need to rollback (ie. failure to binlog the transaction), we crash the
-   server (!)
-
- - If we crash during commit, it is possible that an application/user can have
-   seen another transaction committed that is not recovered by XA crash
-   recovery. Thus durability is partially lost. However, consistency is still
-   guaranteed, we never recover a transaction and not recover another
-   transaction that committed before. */
-static
-void
-innobase_prepare_ordered(
-/*============*/
-	handlerton *hton, /*!< in: Innodb handlerton */
-	THD*	thd,	/*!< in: MySQL thread handle of the user for whom
-			the transaction should be committed */
-	bool	all)	/*!< in:	TRUE - commit transaction
-				FALSE - the current SQL statement ended */
-{
-	trx_t*		trx;
-	DBUG_ENTER("innobase_prepare_ordered");
-	DBUG_ASSERT(hton == innodb_hton_ptr);
-
-	trx = check_trx_exists(thd);
-
-	mutex_enter(&kernel_mutex);
-	lock_release_off_kernel(trx);
-	mutex_exit(&kernel_mutex);
-
-	DBUG_VOID_RETURN;
-}
-
 static
 void
 innobase_commit_ordered_2(
@@ -3088,16 +3035,6 @@ innobase_rollback(
 
 	row_unlock_table_autoinc_for_mysql(trx);
 
-	/* if transaction has already released locks, it is too late to
-	rollback */
-	if (innobase_release_locks_early && trx->conc_state == TRX_PREPARED
-	    && UT_LIST_GET_LEN(trx->trx_locks) == 0) {
-		sql_print_error("Rollback after releasing locks! "
-				"errno=%d, dberr="ULINTPF,
-				errno, trx->error_state);
-		ut_error;
-	}
-
 	if (all
 		|| !thd_test_options(thd, OPTION_NOT_AUTOCOMMIT | OPTION_BEGIN)) {
 
@@ -11968,11 +11905,6 @@ static	MYSQL_SYSVAR_ULINT(pass_corrupt_table, srv_pass_corrupt_table,
   "except for the deletion.",
   NULL, NULL, 0, 0, 1, 0);
 
-static MYSQL_SYSVAR_BOOL(release_locks_early, innobase_release_locks_early,
-  PLUGIN_VAR_READONLY,
-  "Release row locks in the prepare stage instead of in the commit stage",
-  NULL, NULL, FALSE);
-
 static MYSQL_SYSVAR_ULINT(lazy_drop_table, srv_lazy_drop_table,
   PLUGIN_VAR_RQCMDARG,
   "At deleting tablespace, only miminum needed processes at the time are done. "
@@ -12070,7 +12002,6 @@ static struct st_mysql_sys_var* innobase_system_variables[]= {
   MYSQL_SYSVAR(auto_lru_dump),
   MYSQL_SYSVAR(use_purge_thread),
   MYSQL_SYSVAR(pass_corrupt_table),
-  MYSQL_SYSVAR(release_locks_early),
   MYSQL_SYSVAR(lazy_drop_table),
   NULL
 };
diff --git a/storage/xtradb/include/srv0srv.h b/storage/xtradb/include/srv0srv.h
index 8bcf215c7ac..ac7ae8c5627 100644
--- a/storage/xtradb/include/srv0srv.h
+++ b/storage/xtradb/include/srv0srv.h
@@ -351,9 +351,6 @@ extern ulint srv_buf_pool_reads;
 /** Time in seconds between automatic buffer pool dumps */
 extern uint srv_auto_lru_dump;
 
-/** Release row locks already in the prepare phase */
-extern my_bool innobase_release_locks_early;
-
 /** Status variables to be passed to MySQL */
 typedef struct export_var_struct export_struc;
 
diff --git a/storage/xtradb/include/trx0sys.ic b/storage/xtradb/include/trx0sys.ic
index f39ba3055be..5e0f07c8b9d 100644
--- a/storage/xtradb/include/trx0sys.ic
+++ b/storage/xtradb/include/trx0sys.ic
@@ -338,12 +338,6 @@ trx_list_get_min_trx_id(void)
 
 /****************************************************************//**
 Checks if a transaction with the given id is active.
-IMPORTANT ASSUMPTION:
-	It is assumed that this function is only used for the purpose of
-	determining if locks need to be created for the input transaction.
-	So if innobase_release_locks_early global option is set, and if
-	the transaction is already in prepared state, this returns FALSE,
-	as locks are no longer needed for the transaction.
 @return	TRUE if active */
 UNIV_INLINE
 ibool
@@ -372,8 +366,7 @@ trx_is_active(
 
 	trx = trx_get_on_id(trx_id);
 	if (trx && (trx->conc_state == TRX_ACTIVE
-		    || (trx->conc_state == TRX_PREPARED &&
-			!innobase_release_locks_early))) {
+		    || trx->conc_state == TRX_PREPARED)) {
 
 		return(TRUE);
 	}
diff --git a/storage/xtradb/srv/srv0srv.c b/storage/xtradb/srv/srv0srv.c
index fb13ec395c2..1e078e1a6e9 100644
--- a/storage/xtradb/srv/srv0srv.c
+++ b/storage/xtradb/srv/srv0srv.c
@@ -496,9 +496,6 @@ UNIV_INTERN FILE*	srv_misc_tmpfile;
 UNIV_INTERN ulint	srv_main_thread_process_no	= 0;
 UNIV_INTERN ulint	srv_main_thread_id		= 0;
 
-/* Release row locks already in the prepare phase */
-UNIV_INTERN my_bool	innobase_release_locks_early	= FALSE;
-
 /* The following count work done by srv_master_thread. */
 
 /* Iterations by the 'once per second' loop. */