Bug#32169848 THD_NDB TRANSACTION FUNCTIONALITY [#5]

Rename "lock_count" to "external_lock_count", increment the variable only when transaction has been registered sucessfully and thus remove two unneccessary decrement calls. Improve description of the "external_lock_count" variable. Change-Id: I5bfa91fdca8fa2d377b170696b6086293d8cb743
ldonoso · May 19, 2021 · f7c43cb · f7c43cb
1 parent 62af1b4
commit f7c43cb
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Showing 2 changed files with 19 additions and 12 deletions.
diff --git a/storage/ndb/plugin/ha_ndbcluster.cc b/storage/ndb/plugin/ha_ndbcluster.cc
@@ -1138,7 +1138,6 @@ Thd_ndb::Thd_ndb(THD *thd)
   connection = ndb_get_cluster_connection();
   m_connect_count = connection->get_connect_count();
   ndb = new Ndb(connection, "");
-  lock_count = 0;
   save_point_count = 0;
   trans = NULL;
   m_handler = NULL;
@@ -7360,29 +7359,30 @@ int ha_ndbcluster::external_lock(THD *thd, int lock_type) {
 
     DBUG_PRINT("enter", ("lock_type != F_UNLCK "
                          "this: %p  thd: %p  thd_ndb: %p  "
-                         "thd_ndb->lock_count: %d",
-                         this, thd, thd_ndb, thd_ndb->lock_count));
+                         "thd_ndb->external_lock_count: %d",
+                         this, thd, thd_ndb, thd_ndb->external_lock_count));
 
-    if ((error = start_statement(thd, thd_ndb, thd_ndb->lock_count++))) {
-      thd_ndb->lock_count--;
+    if ((error = start_statement(thd, thd_ndb, thd_ndb->external_lock_count))) {
       return error;
     }
     if ((error = init_handler_for_statement(thd))) {
-      thd_ndb->lock_count--;
       return error;
     }
+    thd_ndb->external_lock_count++;
     return 0;
   } else {
     Thd_ndb *thd_ndb = m_thd_ndb;
     assert(thd_ndb);
 
     DBUG_PRINT("enter", ("lock_type == F_UNLCK "
                          "this: %p  thd: %p  thd_ndb: %p  "
-                         "thd_ndb->lock_count: %d",
-                         this, thd, thd_ndb, thd_ndb->lock_count));
+                         "thd_ndb->external_lock_count: %d",
+                         this, thd, thd_ndb, thd_ndb->external_lock_count));
+
+    thd_ndb->external_lock_count--;
+    if (thd_ndb->external_lock_count == 0) {
+      DBUG_PRINT("trans", ("Last external_lock() unlock"));
 
-    if (!--thd_ndb->lock_count) {
-      DBUG_PRINT("trans", ("Last external_lock"));
       const bool autocommit_enabled =
           !thd_test_options(thd, OPTION_NOT_AUTOCOMMIT | OPTION_BEGIN);
       // Only the 'CREATE TABLE ... SELECT' variant of the
@@ -7392,7 +7392,7 @@ int ha_ndbcluster::external_lock(THD *thd, int lock_type) {
 
       if (thd_ndb->trans && (autocommit_enabled || is_create_table_select)) {
         /*
-          Unlock is done without a transaction commit / rollback.
+          Unlock is done without transaction commit / rollback.
           This happens if the thread didn't update any rows as a part of normal
           DMLs or `CREATE TABLE ... SELECT` DDL .
           We must in this case close the transaction to release resources

diff --git a/storage/ndb/plugin/ndb_thd_ndb.h b/storage/ndb/plugin/ndb_thd_ndb.h
@@ -54,7 +54,14 @@ class Thd_ndb {
   class Ndb_cluster_connection *connection;
   class Ndb *ndb;
   class ha_ndbcluster *m_handler;
-  uint lock_count;
+
+  // Reference counter for external_lock() calls. The counter controls that
+  // the handlerton is registered as being part of the MySQL transaction only at
+  // the first external_lock() call (when the counter is zero). Also the counter
+  // controls that any started NDB transaction is closed when external_lock(..,
+  // F_UNLOCK) is called for the last time (i.e when the counter is back to zero
+  // again).
+  uint external_lock_count{0};
 
   // Reference counter for start_stmt() calls. The counter controls that the
   // handlerton is registered as being part of the MySQL transaction at the