MDEV-38822: Fix self-deadlock on CTAS from innodb stats tables

mysql-test/suite/innodb/r/alter_copy_stats.result

@@ -104,12 +104,17 @@ n_rows	database_name	lower(table_name)
 DROP TABLE t1;
 DROP TABLE t2;
 #
-# MDEV-38667 Assertion in diagnostics area on DDL stats timeout
+# MDEV-38822 Lock wait timeout does not happen anymore
 #
 set @lock_wait_timeout= @@global.innodb_lock_wait_timeout;
 SET innodb_lock_wait_timeout = 1;
 CREATE TABLE t ENGINE=InnoDB AS SELECT * FROM mysql.innodb_table_stats;
-Warnings:
-Warning	1088	Error updating stats for table after table rebuild: Lock wait timeout
 SET innodb_lock_wait_timeout = @lock_wait_timeout;
+SELECT COUNT(*) as n_rows FROM t;
+n_rows
+1
+# For a deterministic test, we wait for the background thread to update the stats for the new table.
+SELECT table_name, n_rows FROM mysql.innodb_table_stats WHERE table_name = 't';
+table_name	n_rows
+t	1
 DROP TABLE t;

mysql-test/suite/innodb/t/alter_copy_stats.test

@@ -90,10 +90,15 @@ DROP TABLE t1;
 DROP TABLE t2;
 
 --echo #
---echo # MDEV-38667 Assertion in diagnostics area on DDL stats timeout
+--echo # MDEV-38822 Lock wait timeout does not happen anymore
 --echo #
 set @lock_wait_timeout= @@global.innodb_lock_wait_timeout;
 SET innodb_lock_wait_timeout = 1;
 CREATE TABLE t ENGINE=InnoDB AS SELECT * FROM mysql.innodb_table_stats;
 SET innodb_lock_wait_timeout = @lock_wait_timeout;
+SELECT COUNT(*) as n_rows FROM t;
+--echo # For a deterministic test, we wait for the background thread to update the stats for the new table.
+--let $wait_condition= SELECT COUNT(*) = 1 FROM mysql.innodb_table_stats WHERE table_name = 't' AND n_rows > 0
+--source include/wait_condition.inc
+SELECT table_name, n_rows FROM mysql.innodb_table_stats WHERE table_name = 't';
 DROP TABLE t;

sql/sql_class.cc

@@ -511,6 +511,19 @@ int thd_sql_command(const THD *thd)
   return (int) thd->lex->sql_command;
 }
 
+extern "C" int thd_sql_is_table_accessed(const MYSQL_THD thd,
+                                         const char *db_name,
+                                         const char *table_name)
+{
+  for (TABLE *table= thd->open_tables; table; table= table->next)
+  {
+    if (!strcmp(table->s->db.str, db_name) &&
+        !strcmp(table->s->table_name.str, table_name))
+      return 1;
+  }
+  return 0;
+}
+
 /*
   Returns options used with DDL's, like IF EXISTS etc...
   Will returns 'nonsense' if the command was not a DDL.

storage/innobase/dict/dict0stats_bg.cc

@@ -97,13 +97,7 @@ static void dict_stats_recalc_pool_deinit()
 		destroy_background_thd(dict_stats_thd);
 }
 
-/*****************************************************************//**
-Add a table to the recalc pool, which is processed by the
-background stats gathering thread. Only the table id is added to the
-list, so the table can be closed after being enqueued and it will be
-opened when needed. If the table does not exist later (has been DROPped),
-then it will be removed from the pool and skipped. */
-static void dict_stats_recalc_pool_add(table_id_t id)
+void dict_stats_recalc_pool_add(table_id_t id)
 {
   ut_ad(!srv_read_only_mode);
   ut_ad(id);

storage/innobase/handler/ha_innodb.cc

@@ -128,7 +128,9 @@ TABLE *get_purge_table(THD *thd);
 TABLE *open_purge_table(THD *thd, const char *db, size_t dblen,
 			const char *tb, size_t tblen);
 void close_thread_tables(THD* thd);
-
+extern "C" int thd_sql_is_table_accessed(const MYSQL_THD thd,
+                                         const char *db_name,
+                                         const char *table_name);
 #ifdef MYSQL_DYNAMIC_PLUGIN
 #define tc_size  400
 #endif
@@ -21299,6 +21301,26 @@ void alter_stats_rebuild(dict_table_t *table, THD *thd)
   if (!table->space || !dict_stats_is_persistent_enabled(table))
     DBUG_VOID_RETURN;
 
+  if (thd && thd_sql_command(thd) == SQLCOM_CREATE_TABLE)
+  {
+    LEX_STRING *q= thd_query_string(thd);
+    if (q->str && q->length > 0)
+    {
+
+      if ((thd_sql_is_table_accessed(thd, "mysql", "innodb_table_stats")) ||
+          thd_sql_is_table_accessed(thd, "mysql", "innodb_index_stats"))
+      {
+        // Avoids a deadlock where a shared lock is held on the
+        // stats system table, then dict_stats_update tries to acquire
+        // an exclusive lock on it. An example is "CREATE TABLE t1 AS SELECT *
+        // FROM innodb_[table/index]_stats".
+        dict_stats_recalc_pool_add(table->id);
+
+        DBUG_VOID_RETURN;
+      }
+    }
+  }
+
   dberr_t ret= dict_stats_update(table, DICT_STATS_RECALC_PERSISTENT);
   if (ret != DB_SUCCESS)
     push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN,

storage/innobase/include/dict0stats.h

@@ -245,3 +245,12 @@ dict_stats_empty_table(
 	dict_table_t*	table,
 	bool		empty_defrag_stats);
 #endif /* dict0stats_h */
+
+/**
+ * @brief Add a table to the recalc pool, which is processed by the
+ * background stats gathering thread. Only the table id is added to the
+ * list, so the table can be closed after being enqueued and it will be
+ * opened when needed. If the table does not exist later (has been DROPped),
+ * then it will be removed from the pool and skipped.
+ */
+void dict_stats_recalc_pool_add(table_id_t id);