MDEV-40388: sequence.simple fails on replay by bsrikanth-mariadb · Pull Request #5427 · MariaDB/server

bsrikanth-mariadb · 2026-07-21T12:55:22Z

When the recording is enabled for the query,
explain select * from seq_15_to_1_step_12345;
it recorded the table context having a DDL definition as: -

CREATE TABLE seq_15_to_1_step_12345 (
-> seq bigint(20) unsigned NOT NULL,
-> PRIMARY KEY (seq)
-> ) ENGINE=SEQUENCE DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci;

Now, when that context is replayed, the DDL statement is executed.
But, we cannot create such the table and instead it errors out saying
ERROR 1050 (42S01): Table 'seq_15_to_1_step_12345' already exists.

The problem is that,
sequence table was determined using tbl->table->s->sequence. The
intention was to not record sequence table information. However, the
check was only partially correct.

Instead, we need an enhanced condition like: -
if (!tbl->is_view() && tbl->table)
{
if (tbl->table->s->sequence ||
lex_string_eq(hton_name(tbl->table->s->db_type()),
STRING_WITH_LEN("SEQUENCE")))
{
continue;
}
}

This makes both the following kinds of queries on sequences, to not
record any table contexts on them: -

explain select * from seq_15_to_1_step_12345;
create sequence s1;
EXPLAIN select * from s1;

gemini-code-assist

Code Review

This pull request updates the logic in Optimizer_context_recorder::dump_sql_script to identify sequence tables by checking if the storage engine name is "SEQUENCE" instead of checking the sequence flag on the table share. The reviewer suggested a performance and code-simplification improvement: accessing the storage engine's handlerton directly from the table share (tbl->table->s->db_type) instead of calling the virtual method partition_ht() on the handler.

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gemini-code-assist · 2026-07-21T12:57:15Z

+    if (!tbl->is_view() && tbl->table)
+    {
+      handlerton *hton= tbl->table->file->partition_ht();
+      const LEX_CSTRING *engine_name= hton_name(hton);
+      if (strcmp(engine_name->str, "SEQUENCE") == 0)
+        continue;
+    }


Instead of calling the virtual method partition_ht() on the handler (tbl->table->file), you can directly access the storage engine's handlerton from the table share (tbl->table->s->db_type). This is more direct, avoids a virtual function call, and simplifies the code.

if (!tbl->is_view() && tbl->table) { const LEX_CSTRING *engine_name= hton_name(tbl->table->s->db_type); if (strcmp(engine_name->str, "SEQUENCE") == 0) continue; }

actually here gemini absolutely right, why not tbl->table->file ?

Why it is SQL_SEQUENCE or SEQUENCE if you need probably one, or could you say what is the difference?

maybe use lex_string_eq ?

Why it is SQL_SEQUENCE or SEQUENCE if you need probably one, or could you say what is the difference?

SEQUENCE is for the following eg: -
explain select * from seq_15_to_1_step_12345;

and SQL_SEQUENCE is for the following eg: -
create sequence s1;
EXPLAIN select * from s1;

actually here gemini absolutely right, why not tbl->table->file ?

For this example
create sequence s1;
EXPLAIN select * from s1;

const LEX_CSTRING *engine_name= hton_name(tbl->table->s->db_type());
is seen as InnoDB or MyISAM, and not SQL_SEQUENCE or SEQUENCE

Copilot

Pull request overview

Fixes MDEV-40388 by ensuring optimizer context recording/replay does not attempt to capture DDL/stats for sequence tables, which can break replay (e.g., sequence.simple).

Changes:

Update Optimizer_context_recorder::dump_sql_script() to skip sequence tables based on storage engine name instead of TABLE_SHARE::sequence.
Add a regression test case to verify sequence tables are not recorded in optimizer context output.
Update the expected result file accordingly.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
`sql/opt_context_store_replay.cc`	Changes sequence-table detection logic to skip recording sequence tables during context dump.
`mysql-test/main/opt_context_store_stats.test`	Adds a regression test query against a sequence under `optimizer_record_context=ON`.
`mysql-test/main/opt_context_store_stats.result`	Records expected output for the new regression test section.

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+    if (!tbl->is_view() && tbl->table)
+    {
+      handlerton *hton= tbl->table->file->partition_ht();
+      const LEX_CSTRING *engine_name= hton_name(hton);
+      if (strcmp(engine_name->str, "SEQUENCE") == 0 ||
+          strcmp(engine_name->str, "SQL_SEQUENCE") == 0)
+      {
+        continue;
+      }
+    }


bsrikanth-mariadb · 2026-07-22T11:02:18Z

+set optimizer_record_context=ON;
+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	
+# == Optimizer Context
+# === Tables
+# Tables in the context
+table_name	file_stat_records	index_name	rec_per_key
+# === Range accesses
+index_name	ranges	num_rows	max_index_blocks	max_row_blocks
+# == End of optimizer context


not required

bsrikanth-mariadb · 2026-07-22T11:04:52Z

+set optimizer_record_context=ON;
+explain select * from seq_15_to_1_step_12345;
+
+--source include/opt_context_list_tables_and_ranges.inc


not required

sanja-byelkin

The direction is correct, but please fix small things and answer questions

sanja-byelkin · 2026-07-22T09:49:31Z

+    if (!tbl->is_view() && tbl->table)
+    {
+      handlerton *hton= tbl->table->file->partition_ht();
+      const LEX_CSTRING *engine_name= hton_name(hton);
+      if (strcmp(engine_name->str, "SEQUENCE") == 0)
+        continue;
+    }


actually here gemini absolutely right, why not tbl->table->file ?

sanja-byelkin · 2026-07-22T09:50:59Z

+    if (!tbl->is_view() && tbl->table)
+    {
+      handlerton *hton= tbl->table->file->partition_ht();
+      const LEX_CSTRING *engine_name= hton_name(hton);
+      if (strcmp(engine_name->str, "SEQUENCE") == 0)
+        continue;
+    }


Why it is SQL_SEQUENCE or SEQUENCE if you need probably one, or could you say what is the difference?

sanja-byelkin · 2026-07-22T09:53:14Z

+set optimizer_record_context=ON;
+explain select * from seq_15_to_1_step_12345;
+
+--source include/opt_context_list_tables_and_ranges.inc


version marker absent

sanja-byelkin · 2026-07-22T09:53:41Z

+
+--echo #
+--echo # MDEV-40388: sequence.simple fails on replay
+--echo # Table context should *not* be recorded for seq 


Trailing spaces are here

sanja-byelkin · 2026-07-22T09:54:32Z

+    if (!tbl->is_view() && tbl->table)
+    {
+      handlerton *hton= tbl->table->file->partition_ht();
+      const LEX_CSTRING *engine_name= hton_name(hton);
+      if (strcmp(engine_name->str, "SEQUENCE") == 0)
+        continue;
+    }


maybe use lex_string_eq ?

vuvova · 2026-07-22T13:12:55Z

Why the test fails on replay? Your commit comment doesn't explain anything besides repeating what the code does.

bsrikanth-mariadb · 2026-07-22T13:48:50Z

Why the test fails on replay? Your commit comment doesn't explain anything besides repeating what the code does.

When the recording is enabled for the query
explain select * from seq_15_to_1_step_12345; it recorded the table context having a DDL definition as: -

CREATE TABLE `seq_15_to_1_step_12345` (
    ->   `seq` bigint(20) unsigned NOT NULL,
    ->   PRIMARY KEY (`seq`)
    -> ) ENGINE=SEQUENCE DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci;

Now, when that context is replayed, the DDL statement is executed. But, we cannot create such the table and instead it errors out
ERROR 1050 (42S01): Table 'seq_15_to_1_step_12345' already exists

When the recording is enabled for the query, explain select * from seq_15_to_1_step_12345; it recorded the table context having a DDL definition as: - CREATE TABLE `seq_15_to_1_step_12345` ( -> `seq` bigint(20) unsigned NOT NULL, -> PRIMARY KEY (`seq`) -> ) ENGINE=SEQUENCE DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci; Now, when that context is replayed, the DDL statement is executed. But, we cannot create such the table and instead it errors out saying ERROR 1050 (42S01): Table 'seq_15_to_1_step_12345' already exists. The problem is that, sequence table was determined using tbl->table->s->sequence. The intention was to not record sequence table information. However, the check was only partially correct. Instead, we need an enhanced condition like: - if (!tbl->is_view() && tbl->table) { if (tbl->table->s->sequence || lex_string_eq(hton_name(tbl->table->s->db_type()), STRING_WITH_LEN("SEQUENCE"))) { continue; } } This makes both the following kinds of queries on sequences, to not record any table contexts on them: - 1. explain select * from seq_15_to_1_step_12345; 2. create sequence s1; EXPLAIN select * from s1;

bsrikanth-mariadb added the MariaDB Corporation label Jul 21, 2026

gemini-code-assist Bot reviewed Jul 21, 2026

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bsrikanth-mariadb force-pushed the 13.1-MDEV-40388-sequence.simple-fails-on-replay branch 2 times, most recently from d78faae to b2f5d98 Compare July 22, 2026 00:48

sanja-byelkin requested a review from Copilot July 22, 2026 09:38

Copilot started reviewing on behalf of sanja-byelkin July 22, 2026 09:38 View session

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sanja-byelkin requested changes Jul 22, 2026

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bsrikanth-mariadb force-pushed the 13.1-MDEV-40388-sequence.simple-fails-on-replay branch from b2f5d98 to 5abaa6b Compare July 22, 2026 11:00

vuvova self-requested a review July 22, 2026 13:13

bsrikanth-mariadb force-pushed the 13.1-MDEV-40388-sequence.simple-fails-on-replay branch from 5abaa6b to fe2e034 Compare July 22, 2026 13:58

bsrikanth-mariadb force-pushed the 13.1-MDEV-40388-sequence.simple-fails-on-replay branch from fe2e034 to a9983bf Compare July 22, 2026 14:40

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vuvova commented Jul 22, 2026

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