MDEV-36487 Fix ha_innobase::check() for sequences

InnoDB does the following check for sequence table during check
table command:
- There should be only one index should exist on sequence table
- There should be only one row should exist on sequence table
- The leaf page must be the root page for the sequence table
- Delete marked record should not exist
- DB_TRX_ID and DB_ROLL_PTR of the record should be 0 and 1U << 55

mysql-test/suite/innodb/r/check_sequence,debug.rdiff

@@ -0,0 +1,17 @@
+--- check_sequence.result
++++ check_sequence,debug.result
+@@ -112,3 +112,14 @@
+ 3
+ disconnect prevent_purge;
+ DROP SEQUENCE s1;
++CREATE SEQUENCE s ENGINE=InnoDB;
++ALTER TABLE s SEQUENCE=0;
++FLUSH TABLES;
++SET STATEMENT DEBUG_DBUG="+d,fail_root_page" FOR
++CHECK TABLE s;
++Table	Op	Msg_type	Msg_text
++test.s	check	Warning	InnoDB: Sequence table test/s is corrupted.
++test.s	check	error	Corrupt
++ALTER TABLE s SEQUENCE=1;
++ERROR HY000: InnoDB: Table `test`.`s` is corrupted.
++DROP SEQUENCE s;

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

@@ -0,0 +1,114 @@
+#
+# MDEV-36487  Fix ha_innobase::check() for sequences
+#
+call mtr.add_suppression("InnoDB: Table test/s2 contains 1 indexes .*");
+call mtr.add_suppression("Table test/s2 has a primary key in InnoDB .*");
+CREATE SEQUENCE s ENGINE=InnoDB;
+ALTER TABLE s SEQUENCE=0, ALGORITHM=INPLACE;
+ERROR 0A000: ALGORITHM=INPLACE is not supported. Reason: SEQUENCE. Try ALGORITHM=COPY
+ALTER TABLE s SEQUENCE=0, ALGORITHM=COPY;
+FLUSH TABLES;
+CHECK TABLE s;
+Table	Op	Msg_type	Msg_text
+test.s	check	Warning	InnoDB: Sequence table test/s has ROLLBACK enabled.
+test.s	check	error	Corrupt
+ALTER TABLE s SEQUENCE=1;
+ERROR HY000: InnoDB: Table `test`.`s` is corrupted.
+DROP SEQUENCE s;
+CREATE SEQUENCE s ENGINE=InnoDB;
+CREATE TABLE s2 LIKE s;
+ALTER TABLE s2 sequence=0;
+INSERT INTO s2 VALUES (3,1,9223372036854775806,1,1,1000,0,0);
+ALTER TABLE s2 ADD INDEX idx(start_value);
+FLUSH TABLES;
+CHECK TABLE s2;
+Table	Op	Msg_type	Msg_text
+test.s2	check	Warning	InnoDB: Table test/s2 contains 1 indexes inside InnoDB, which is different from the number of indexes 0 defined in the MariaDB 
+test.s2	check	Warning	InnoDB: Sequence table test/s2 does have more than one indexes.
+test.s2	check	error	Corrupt
+ALTER TABLE s2 SEQUENCE=1;
+ERROR HY000: InnoDB: Table `test`.`s2` is corrupted.
+DROP SEQUENCE s;
+DROP SEQUENCE s2;
+CREATE SEQUENCE s ENGINE=InnoDB;
+CREATE TABLE s2 LIKE s;
+ALTER TABLE s2 sequence=0;
+INSERT INTO s2 VALUES (3,2,9223372036854775806,2,2,1000,0,0);
+ALTER TABLE s2 ADD PRIMARY KEY(start_value);
+FLUSH TABLES;
+CHECK TABLE s2;
+Table	Op	Msg_type	Msg_text
+test.s2	check	Warning	InnoDB: Table test/s2 has a primary key in InnoDB data dictionary, but not in MariaDB!
+test.s2	check	Warning	InnoDB: Table test/s2 contains 1 indexes inside InnoDB, which is different from the number of indexes 0 defined in the MariaDB 
+test.s2	check	Warning	InnoDB: Sequence table test/s2 does not have generated clustered index.
+test.s2	check	error	Corrupt
+ALTER TABLE s2 SEQUENCE=1;
+ERROR HY000: InnoDB: Table `test`.`s2` is corrupted.
+DROP SEQUENCE s;
+DROP SEQUENCE s2;
+CREATE SEQUENCE s ENGINE=InnoDB;
+CREATE TABLE s2 LIKE s;
+ALTER TABLE s2 sequence=0;
+INSERT INTO s2 VALUES (3,1,9223372036854775806,1,1,1000,0,0);
+DELETE FROM s2;
+InnoDB		0 transactions not purged
+FLUSH TABLES;
+CHECK TABLE s2;
+Table	Op	Msg_type	Msg_text
+test.s2	check	Warning	InnoDB: Should have only one record in sequence table test/s2. But it has 0 records.
+test.s2	check	error	Corrupt
+ALTER TABLE s2 SEQUENCE=1;
+ERROR HY000: InnoDB: Table `test`.`s2` is corrupted.
+DROP SEQUENCE s;
+DROP SEQUENCE s2;
+CREATE SEQUENCE s ENGINE=InnoDB;
+CREATE TABLE s2 LIKE s;
+ALTER TABLE s2 sequence=0;
+INSERT INTO s2 select seq, seq, seq, seq, seq, seq, 1, seq from
+seq_1_to_200;
+FLUSH TABLES;
+CHECK TABLE s2;
+Table	Op	Msg_type	Msg_text
+test.s2	check	Warning	InnoDB: Non leaf page exists for sequence table test/s2.
+test.s2	check	error	Corrupt
+ALTER TABLE s2 SEQUENCE=1;
+ERROR HY000: InnoDB: Table `test`.`s2` is corrupted.
+DROP SEQUENCE s;
+DROP SEQUENCE s2;
+CREATE SEQUENCE s ENGINE=InnoDB;
+CREATE TABLE s2 LIKE s;
+ALTER TABLE s2 sequence=0;
+DELETE FROM s2;
+InnoDB		0 transactions not purged
+connect  prevent_purge,localhost,root;
+START TRANSACTION WITH CONSISTENT SNAPSHOT;
+connection default;
+INSERT INTO s2 VALUES (3,1,9223372036854775806,1,1,1000,0,0);
+FLUSH TABLES;
+CHECK TABLE s2;
+Table	Op	Msg_type	Msg_text
+test.s2	check	Warning	InnoDB: Record in sequence table test/s2 is corrupted.
+test.s2	check	error	Corrupt
+ALTER TABLE s2 SEQUENCE=1;
+ERROR HY000: InnoDB: Table `test`.`s2` is corrupted.
+DROP SEQUENCE s;
+DROP SEQUENCE s2;
+CREATE SEQUENCE s1 ENGINE=InnoDB;
+CHECK TABLE s1;
+Table	Op	Msg_type	Msg_text
+test.s1	check	status	OK
+connection prevent_purge;
+START TRANSACTION WITH CONSISTENT SNAPSHOT;
+connection default;
+INSERT INTO s1 VALUES (3,1,9223372036854775806,1,1,1000,0,0);
+SELECT * FROM s1;
+next_not_cached_value	minimum_value	maximum_value	start_value	increment	cache_size	cycle_option	cycle_count
+3	1	9223372036854775806	1	1	1000	0	0
+CHECK TABLE s1;
+Table	Op	Msg_type	Msg_text
+test.s1	check	status	OK
+select nextval(s1);
+nextval(s1)
+3
+disconnect prevent_purge;
+DROP SEQUENCE s1;

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

@@ -0,0 +1,136 @@
+--source include/have_innodb.inc
+--source include/have_sequence.inc
+--source include/maybe_debug.inc
+--echo #
+--echo # MDEV-36487  Fix ha_innobase::check() for sequences
+--echo #
+
+call mtr.add_suppression("InnoDB: Table test/s2 contains 1 indexes .*");
+call mtr.add_suppression("Table test/s2 has a primary key in InnoDB .*");
+# Sequence table which has NO_ROLLBACK flag set
+let $datadir=`select @@datadir`;
+CREATE SEQUENCE s ENGINE=InnoDB;
+copy_file $datadir/test/s.frm $datadir/test/s1.frm;
+--error ER_ALTER_OPERATION_NOT_SUPPORTED_REASON
+ALTER TABLE s SEQUENCE=0, ALGORITHM=INPLACE;
+ALTER TABLE s SEQUENCE=0, ALGORITHM=COPY;
+FLUSH TABLES;
+remove_file $datadir/test/s.frm;
+move_file $datadir/test/s1.frm $datadir/test/s.frm;
+CHECK TABLE s;
+--error ER_TABLE_CORRUPT
+ALTER TABLE s SEQUENCE=1;
+DROP SEQUENCE s;
+
+# Checks for more than one index
+CREATE SEQUENCE s ENGINE=InnoDB;
+copy_file $datadir/test/s.frm $datadir/test/orig.frm;
+CREATE TABLE s2 LIKE s;
+ALTER TABLE s2 sequence=0;
+INSERT INTO s2 VALUES (3,1,9223372036854775806,1,1,1000,0,0);
+ALTER TABLE s2 ADD INDEX idx(start_value);
+FLUSH TABLES;
+move_file $datadir/test/orig.frm $datadir/test/s2.frm;
+CHECK TABLE s2;
+--error ER_TABLE_CORRUPT
+ALTER TABLE s2 SEQUENCE=1;
+DROP SEQUENCE s;
+DROP SEQUENCE s2;
+
+# Checks for generated clustered index
+CREATE SEQUENCE s ENGINE=InnoDB;
+copy_file $datadir/test/s.frm $datadir/test/orig.frm;
+CREATE TABLE s2 LIKE s;
+ALTER TABLE s2 sequence=0;
+INSERT INTO s2 VALUES (3,2,9223372036854775806,2,2,1000,0,0);
+ALTER TABLE s2 ADD PRIMARY KEY(start_value);
+FLUSH TABLES;
+move_file $datadir/test/orig.frm $datadir/test/s2.frm;
+CHECK TABLE s2;
+--error ER_TABLE_CORRUPT
+ALTER TABLE s2 SEQUENCE=1;
+DROP SEQUENCE s;
+DROP SEQUENCE s2;
+
+# Should contain only one record
+CREATE SEQUENCE s ENGINE=InnoDB;
+copy_file $datadir/test/s.frm $datadir/test/orig.frm;
+CREATE TABLE s2 LIKE s;
+ALTER TABLE s2 sequence=0;
+INSERT INTO s2 VALUES (3,1,9223372036854775806,1,1,1000,0,0);
+DELETE FROM s2;
+--source include/wait_all_purged.inc
+FLUSH TABLES;
+move_file $datadir/test/orig.frm $datadir/test/s2.frm;
+CHECK TABLE s2;
+--error ER_TABLE_CORRUPT
+ALTER TABLE s2 SEQUENCE=1;
+DROP SEQUENCE s;
+DROP SEQUENCE s2;
+
+# More than one page
+CREATE SEQUENCE s ENGINE=InnoDB;
+copy_file $datadir/test/s.frm $datadir/test/orig.frm;
+CREATE TABLE s2 LIKE s;
+ALTER TABLE s2 sequence=0;
+INSERT INTO s2 select seq, seq, seq, seq, seq, seq, 1, seq from
+seq_1_to_200;
+FLUSH TABLES;
+move_file $datadir/test/orig.frm $datadir/test/s2.frm;
+CHECK TABLE s2;
+--error ER_TABLE_CORRUPT
+ALTER TABLE s2 SEQUENCE=1;
+DROP SEQUENCE s;
+DROP SEQUENCE s2;
+
+# Checks for DB_TRX_ID & DB_ROLL_PTR in the record
+CREATE SEQUENCE s ENGINE=InnoDB;
+copy_file $datadir/test/s.frm $datadir/test/orig.frm;
+CREATE TABLE s2 LIKE s;
+ALTER TABLE s2 sequence=0;
+DELETE FROM s2;
+--source include/wait_all_purged.inc
+--connect (prevent_purge,localhost,root)
+START TRANSACTION WITH CONSISTENT SNAPSHOT;
+--connection default
+INSERT INTO s2 VALUES (3,1,9223372036854775806,1,1,1000,0,0);
+FLUSH TABLES;
+move_file $datadir/test/orig.frm $datadir/test/s2.frm;
+CHECK TABLE s2;
+--error ER_TABLE_CORRUPT
+ALTER TABLE s2 SEQUENCE=1;
+DROP SEQUENCE s;
+DROP SEQUENCE s2;
+
+# Insert a row into a sequence table updates that row
+CREATE SEQUENCE s1 ENGINE=InnoDB;
+CHECK TABLE s1;
+
+--connection prevent_purge
+START TRANSACTION WITH CONSISTENT SNAPSHOT;
+
+--connection default
+INSERT INTO s1 VALUES (3,1,9223372036854775806,1,1,1000,0,0);
+SELECT * FROM s1;
+CHECK TABLE s1;
+--disable_ps2_protocol
+select nextval(s1);
+--enable_ps2_protocol
+--disconnect prevent_purge
+DROP SEQUENCE s1;
+
+if ($have_debug)
+{
+# Root page is corrupted
+CREATE SEQUENCE s ENGINE=InnoDB;
+copy_file $datadir/test/s.frm $datadir/test/s1.frm;
+ALTER TABLE s SEQUENCE=0;
+FLUSH TABLES;
+remove_file $datadir/test/s.frm;
+move_file $datadir/test/s1.frm $datadir/test/s.frm;
+SET STATEMENT DEBUG_DBUG="+d,fail_root_page" FOR
+CHECK TABLE s;
+--error ER_TABLE_CORRUPT
+ALTER TABLE s SEQUENCE=1;
+DROP SEQUENCE s;
+}

mysql-test/suite/sql_sequence/check.result

@@ -120,12 +120,16 @@ drop sequence s;
 #
 CREATE SEQUENCE s engine=innodb;
 ALTER TABLE s sequence=0;
+connect  prevent_purge,localhost,root;
+START TRANSACTION WITH CONSISTENT SNAPSHOT;
+connection default;
 delete from s;
 FLUSH TABLES;
 CHECK TABLE s;
 Table	Op	Msg_type	Msg_text
-test.s	check	Error	Fewer than one row in the table
+test.s	check	Warning	InnoDB: Encountered delete marked record in sequence table test/s.
 test.s	check	error	Corrupt
+disconnect prevent_purge;
 DROP SEQUENCE s;
 CREATE SEQUENCE s engine=innodb;
 CHECK TABLE s;
@@ -138,6 +142,6 @@ insert into s values (2,1,9223372036854775806,1,1,1000,0,0);
 FLUSH TABLES;
 CHECK TABLE s;
 Table	Op	Msg_type	Msg_text
-test.s	check	Warning	More than one row in the table
+test.s	check	Warning	InnoDB: Should have only one record in sequence table test/s. But it has 2 records.
-test.s	check	status	OK
+test.s	check	error	Corrupt
 DROP SEQUENCE s;

mysql-test/suite/sql_sequence/check.test

@@ -147,11 +147,16 @@ let $datadir=`select @@datadir`;
 CREATE SEQUENCE s engine=innodb;
 copy_file $datadir/test/s.frm $datadir/test/s1.frm;
 ALTER TABLE s sequence=0;
+--connect (prevent_purge,localhost,root)
+START TRANSACTION WITH CONSISTENT SNAPSHOT;
+
+--connection default
 delete from s;
 FLUSH TABLES;
 remove_file $datadir/test/s.frm;
 move_file $datadir/test/s1.frm $datadir/test/s.frm;
 CHECK TABLE s;
+--disconnect prevent_purge
 DROP SEQUENCE s;
 
 # Just one row, check ok

storage/innobase/handler/ha_innodb.cc

@@ -15197,6 +15197,117 @@ ha_innobase::optimize(
 	return try_alter ? HA_ADMIN_TRY_ALTER : HA_ADMIN_OK;
 }
 
+/** Does the following validation check for the sequence table
+1) Check whether the InnoDB table has no_rollback flags
+2) Should have only one primary index
+3) Root index page must be leaf page
+4) There should be only one record in leaf page
+5) There shouldn't be delete marked record in leaf page
+6) DB_TRX_ID, DB_ROLL_PTR in the record should be 0 and 1U << 55
+@param thd   Thread
+@param table InnoDB table
+@retval true if validation succeeds or false if validation fails */
+static bool innobase_sequence_table_check(THD *thd, dict_table_t *table)
+{
+  fil_space_t *space= table->space;
+  dict_index_t *clust_index= dict_table_get_first_index(table);
+  mtr_t mtr;
+  bool corruption= false;
+  const rec_t *rec= nullptr;
+  buf_block_t *root_block= nullptr;
+
+  if (UT_LIST_GET_LEN(table->indexes) != 1)
+  {
+    push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN, ER_NOT_KEYFILE,
+			"InnoDB: Sequence table %s does have more than one "
+                        "indexes.", table->name.m_name);
+    corruption= true;
+    goto func_exit;
+  }
+
+  if (!clust_index->is_gen_clust())
+  {
+    push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN, ER_NOT_KEYFILE,
+			"InnoDB: Sequence table %s does not have generated "
+                        "clustered index.", table->name.m_name);
+    corruption= true;
+    goto func_exit;
+  }
+
+  mtr.start();
+  mtr.set_named_space(space);
+  root_block= buf_page_get_gen(page_id_t(space->id, clust_index->page),
+                               space->zip_size(), RW_S_LATCH, nullptr, BUF_GET,
+                               &mtr);
+  DBUG_EXECUTE_IF("fail_root_page", root_block= nullptr;);
+  if (!root_block)
+  {
+    push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN, ER_NOT_KEYFILE,
+			"InnoDB: Sequence table %s is corrupted.",
+                        table->name.m_name);
+    corruption= true;
+    goto err_exit;
+  }
+
+  if (!page_is_leaf(root_block->page.frame))
+  {
+    push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN, ER_NOT_KEYFILE,
+			"InnoDB: Non leaf page exists for sequence table %s.",
+                        table->name.m_name);
+    corruption= true;
+    goto err_exit;
+  }
+
+  if (page_get_n_recs(root_block->page.frame) != 1)
+  {
+    push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN, ER_NOT_KEYFILE,
+			"InnoDB: Should have only one record in sequence "
+                        "table %s. But it has %u records.", table->name.m_name,
+                        page_get_n_recs(root_block->page.frame));
+    corruption= true;
+    goto err_exit;
+  }
+
+  rec= page_rec_get_next(page_get_infimum_rec(root_block->page.frame));
+
+  if (rec_get_deleted_flag(rec, dict_table_is_comp(table)))
+  {
+    corruption= true;
+    push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN, ER_NOT_KEYFILE,
+			"InnoDB: Encountered delete marked record in sequence "
+                        "table %s.", table->name.m_name);
+     goto err_exit;
+  }
+
+  if (trx_read_trx_id(rec + clust_index->trx_id_offset) != 0 ||
+      trx_read_roll_ptr(rec + clust_index->trx_id_offset + DATA_TRX_ID_LEN) !=
+        roll_ptr_t{1} << ROLL_PTR_INSERT_FLAG_POS)
+  {
+    corruption= true;
+    push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN, ER_NOT_KEYFILE,
+			"InnoDB: Record in sequence table %s is corrupted.",
+                        table->name.m_name);
+    goto err_exit;
+  }
+
+  if (!table->no_rollback())
+  {
+    push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN, ER_NOT_KEYFILE,
+			"InnoDB: Sequence table %s has ROLLBACK enabled.",
+                        table->name.m_name);
+    corruption= true;
+  }
+err_exit:
+  mtr.commit();
+func_exit:
+  if (corruption)
+  {
+    dict_set_corrupted(clust_index, "Table corruption");
+    return false;
+  }
+  return true;
+}
+
 /*******************************************************************//**
 Tries to check that an InnoDB table is not corrupted. If corruption is
 noticed, prints to stderr information about it. In case of corruption
@@ -15265,6 +15376,11 @@ ha_innobase::check(
 			table->s->table_name.str);
 
 		DBUG_RETURN(HA_ADMIN_CORRUPT);
+	} else if (table->s->table_type == TABLE_TYPE_SEQUENCE) {
+		DBUG_RETURN(
+		  innobase_sequence_table_check(thd, m_prebuilt->table)
+		  ? HA_ADMIN_OK
+		  : HA_ADMIN_CORRUPT);
 	}
 
 	m_prebuilt->trx->op_info = "checking table";