MDEV-40388 Optimizer context records unusable DDL for SEQUENCE tables

mysql-test/main/opt_trace_store_ddls_sequence.result

@@ -0,0 +1,47 @@
+#
+# MDEV-40388: sequence.simple fails on replay
+#
+# Auto-generated SEQUENCE-engine tables (seq_<from>_to_<to>[_step_<step>])
+# are discovered by the engine from their name and cannot be recreated
+# with an explicit CREATE TABLE. Their DDL must therefore NOT be recorded
+# into the optimizer trace, otherwise replaying the recorded context
+# fails with "Table '...' already exists".
+#
+create database db1;
+use db1;
+create table t1 (a int, b int);
+insert into t1 values (1,2),(2,3);
+set optimizer_trace=1;
+set optimizer_record_context=ON;
+#
+# A query over an auto-generated sequence table only.
+# No ddl should be recorded for the sequence table.
+#
+explain select * from seq_15_to_1_step_12345;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	seq_15_to_1_step_12345	ALL	NULL	NULL	NULL	NULL	1	
+set @ddls= (select json_detailed(json_extract(trace, '$**.ddl'))
+from information_schema.optimizer_trace);
+select ddl
+from json_table(@ddls, '$[*]' columns(ddl text path '$')) as jt;
+ddl
+#
+# A query joining a regular table with a sequence table.
+# Only the regular table t1 should have its ddl recorded.
+#
+select t1.a from t1, seq_1_to_10 where t1.a = seq;
+a
+1
+2
+set @ddls= (select json_detailed(json_extract(trace, '$**.ddl'))
+from information_schema.optimizer_trace);
+select ddl
+from json_table(@ddls, '$[*]' columns(ddl text path '$')) as jt;
+ddl
+CREATE TABLE `t1` (
+  `a` int(11) DEFAULT NULL,
+  `b` int(11) DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci
+set optimizer_record_context=OFF;
+set optimizer_trace=0;
+drop database db1;

mysql-test/main/opt_trace_store_ddls_sequence.test

@@ -0,0 +1,46 @@
+--source include/not_embedded.inc
+--source include/have_sequence.inc
+--source include/no_view_protocol.inc
+
+--echo #
+--echo # MDEV-40388: sequence.simple fails on replay
+--echo #
+--echo # Auto-generated SEQUENCE-engine tables (seq_<from>_to_<to>[_step_<step>])
+--echo # are discovered by the engine from their name and cannot be recreated
+--echo # with an explicit CREATE TABLE. Their DDL must therefore NOT be recorded
+--echo # into the optimizer trace, otherwise replaying the recorded context
+--echo # fails with "Table '...' already exists".
+--echo #
+
+create database db1;
+use db1;
+create table t1 (a int, b int);
+insert into t1 values (1,2),(2,3);
+
+set optimizer_trace=1;
+set optimizer_record_context=ON;
+
+--echo #
+--echo # A query over an auto-generated sequence table only.
+--echo # No ddl should be recorded for the sequence table.
+--echo #
+explain select * from seq_15_to_1_step_12345;
+set @ddls= (select json_detailed(json_extract(trace, '$**.ddl'))
+            from information_schema.optimizer_trace);
+select ddl
+from json_table(@ddls, '$[*]' columns(ddl text path '$')) as jt;
+
+--echo #
+--echo # A query joining a regular table with a sequence table.
+--echo # Only the regular table t1 should have its ddl recorded.
+--echo #
+select t1.a from t1, seq_1_to_10 where t1.a = seq;
+set @ddls= (select json_detailed(json_extract(trace, '$**.ddl'))
+            from information_schema.optimizer_trace);
+select ddl
+from json_table(@ddls, '$[*]' columns(ddl text path '$')) as jt;
+
+set optimizer_record_context=OFF;
+set optimizer_trace=0;
+
+drop database db1;

sql/handler.h

@@ -1926,6 +1926,7 @@ handlerton *ha_default_tmp_handlerton(THD *thd);
 #define HTON_ALTER_NOT_SUPPORTED     (1 << 1) //Engine does not support alter
 #define HTON_CAN_RECREATE            (1 << 2) //Delete all is used for truncate
 #define HTON_HIDDEN                  (1 << 3) //Engine does not appear in lists
+#define HTON_TABLE_EXISTS_BY_NAME    (1 << 4) //Tables auto-discovered from name; reject CREATE TABLE (e.g. SEQUENCE)
 #define HTON_NOT_USER_SELECTABLE     (1 << 5)
 #define HTON_TEMPORARY_NOT_SUPPORTED (1 << 6) //Having temporary tables not supported
 #define HTON_SUPPORT_LOG_TABLES      (1 << 7) //Engine supports log tables

sql/opt_trace_ddl_info.cc

@@ -62,6 +62,7 @@ static const uchar *get_rec_key(const void *entry_, size_t *length,
      - INFORMATION_SCHEMA tables
      - Tables in PERFORMANCE_SCHEMA and mysql database
      - Internal temporary ("work") tables
+     - Tables auto-discovered from their name (e.g. SEQUENCE), which reject CREATE TABLE
 */
 static bool is_base_table(TABLE_LIST *tbl)
 {
@@ -73,7 +74,9 @@ static bool is_base_table(TABLE_LIST *tbl)
      get_table_category(tbl->get_db_name(), tbl->get_table_name()) ==
        TABLE_CATEGORY_USER &&
      tbl->table->s->tmp_table != INTERNAL_TMP_TABLE &&
-     tbl->table->s->tmp_table != SYSTEM_TMP_TABLE);
+     tbl->table->s->tmp_table != SYSTEM_TMP_TABLE &&
+     !(tbl->table->s->db_type() &&
+       (tbl->table->s->db_type()->flags & HTON_TABLE_EXISTS_BY_NAME)));
 }
 
 static bool dump_record_to_trace(THD *thd, DDL_Key *ddl_key, String *stmt)

storage/sequence/sequence.cc

@@ -531,6 +531,7 @@ static int init(void *p)
   hton->drop_table= drop_table;
   hton->discover_table= discover_table;
   hton->discover_table_existence= discover_table_existence;
+  hton->flags|= HTON_TABLE_EXISTS_BY_NAME;
   hton->commit= hton->rollback= [](THD *, bool) { return 0; };
   hton->savepoint_set= hton->savepoint_rollback= hton->savepoint_release=
     [](THD *, void *) { return 0; };