MDEV-36032 Check whether a table can be a sequence when ALTERed with SEQUENCE=1

Thirunarayanan · Thirunarayanan · commit 37274ae01f19 · 2025-06-06T18:42:16.000+05:30
To check the rows, the table needs to be opened. To that end, and like MDEV-36038, we force COPY algorithm on ALTER TABLE ... SEQUENCE=1. This also results in checking the sequence state / metadata. The table structure was already validated before this patch. (cherry picked from commit 6f8ef26)
diff --git a/mysql-test/suite/sql_sequence/alter.result b/mysql-test/suite/sql_sequence/alter.result
@@ -420,6 +420,76 @@ DROP SEQUENCE s2;
 # End of 10.6 tests
 #
 #
+# MDEV-36032 Check when doing ALTER TABLE table_name sequence=1 that table can be a sequence
+#
+create sequence s;
+alter table s sequence=0;
+insert into s values (3,1,9223372036854775806,1,1,1000,0,0);
+alter table s sequence=1;
+ERROR HY000: More than one row in the table
+drop table s;
+create sequence s;
+alter table s sequence=0;
+delete from s;
+insert into s values (2,500,200,1,1,1000,0,0);
+select * from s;
+next_not_cached_value	minimum_value	maximum_value	start_value	increment	cache_size	cycle_option	cycle_count
+2	500	200	1	1	1000	0	0
+alter table s sequence=1;
+ERROR HY000: Sequence 'test.s' has out of range value for options
+check table s;
+Table	Op	Msg_type	Msg_text
+test.s	check	status	OK
+select * from s;
+next_not_cached_value	minimum_value	maximum_value	start_value	increment	cache_size	cycle_option	cycle_count
+2	500	200	1	1	1000	0	0
+check table s;
+Table	Op	Msg_type	Msg_text
+test.s	check	status	OK
+drop table s;
+CREATE TABLE `s` (
+# `next_not_cached_value` bigint(21) NOT NULL,
+`minimum_value` bigint(21) NOT NULL,
+`maximum_value` bigint(21) NOT NULL,
+`start_value` bigint(21) NOT NULL COMMENT 'start value when sequences is created or value if RESTART is used',
+`increment` bigint(21) NOT NULL COMMENT 'increment value',
+`cache_size` bigint(21) unsigned NOT NULL,
+`cycle_option` tinyint(1) unsigned NOT NULL COMMENT '0 if no cycles are allowed, 1 if the sequence should begin a new cycle when maximum_value is passed',
+`cycle_count` bigint(21) NOT NULL COMMENT 'How many cycles have been done'
+) ENGINE=innodb;
+alter table s sequence=1;
+ERROR HY000: Sequence 'test.s' table structure is invalid (Wrong number of columns)
+drop table s;
+create sequence s;
+alter table s drop column next_not_cached_value;
+ERROR HY000: Sequence 'test.s' table structure is invalid (Wrong number of columns)
+drop sequence s;
+CREATE TABLE `s1` (
+`next_not_cached_value` bigint(21) NOT NULL,
+`minimum_value` bigint(21) NOT NULL,
+`maximum_value` bigint(21) NOT NULL,
+`start_value` bigint(21) NOT NULL COMMENT 'start value when sequences is created or value if RESTART is used',
+`increment` bigint(21) NOT NULL COMMENT 'increment value',
+`cache_size` bigint(21) unsigned NOT NULL,
+`cycle_option` tinyint(1) unsigned NOT NULL COMMENT '0 if no cycles are allowed, 1 if the sequence should begin a new cycle when maximum_value is passed',
+`cycle_count` bigint(21) NOT NULL COMMENT 'How many cycles have been done'
+) ENGINE=innodb;
+alter table s1 sequence=1;
+ERROR HY000: Fewer than one row in the table
+alter table s1 sequence=0;
+insert into s1 values (1,1,9223372036854775806,1,1,1000,0,0);
+alter table s1 sequence=1;
+alter table s1 sequence=0;
+insert into s1 values (2,1,9223372036854775806,1,1,1000,0,0);
+alter table s1 sequence=1;
+ERROR HY000: More than one row in the table
+alter table s1 sequence=0;
+insert into s1 values (3,1,9223372036854775806,1,1,1000,0,0);
+alter table s1 sequence=1;
+ERROR HY000: More than one row in the table
+drop table s1;
+# End of 10.11 tests
+#
 # MDEV-28152 Features for sequence
 #
 create sequence s maxvalue 12345;
diff --git a/mysql-test/suite/sql_sequence/alter.test b/mysql-test/suite/sql_sequence/alter.test
@@ -294,6 +294,87 @@ DROP SEQUENCE s2;
 --echo # End of 10.6 tests
 --echo #
 
+--echo #
+--echo # MDEV-36032 Check when doing ALTER TABLE table_name sequence=1 that table can be a sequence
+--echo #
+
+## Too many rows
+create sequence s;
+alter table s sequence=0;
+insert into s values (3,1,9223372036854775806,1,1,1000,0,0);
+--error ER_SEQUENCE_TABLE_HAS_TOO_MANY_ROWS
+alter table s sequence=1;
+drop table s;
+
+## Insert a wrong row (min > max)
+create sequence s;
+alter table s sequence=0;
+delete from s;
+insert into s values (2,500,200,1,1,1000,0,0);
+select * from s;
+--error ER_SEQUENCE_INVALID_DATA
+alter table s sequence=1;
+check table s;
+select * from s;
+check table s;
+drop table s;
+
+## Invalid table structure (already implemented before MDEV-36032)
+CREATE TABLE `s` (
+  # `next_not_cached_value` bigint(21) NOT NULL,
+  `minimum_value` bigint(21) NOT NULL,
+  `maximum_value` bigint(21) NOT NULL,
+  `start_value` bigint(21) NOT NULL COMMENT 'start value when sequences is created or value if RESTART is used',
+  `increment` bigint(21) NOT NULL COMMENT 'increment value',
+  `cache_size` bigint(21) unsigned NOT NULL,
+  `cycle_option` tinyint(1) unsigned NOT NULL COMMENT '0 if no cycles are allowed, 1 if the sequence should begin a new cycle when maximum_value is passed',
+  `cycle_count` bigint(21) NOT NULL COMMENT 'How many cycles have been done'
+) ENGINE=innodb;
+--error ER_SEQUENCE_INVALID_TABLE_STRUCTURE
+alter table s sequence=1;
+drop table s;
+
+## Altering a sequence table to a wrong structure is detected (already
+## implemented before MDEV-36032)
+create sequence s;
+--error ER_SEQUENCE_INVALID_TABLE_STRUCTURE
+alter table s drop column next_not_cached_value;
+drop sequence s;
+
+## Create a normal table then alter to sequence
+CREATE TABLE `s1` (
+`next_not_cached_value` bigint(21) NOT NULL,
+`minimum_value` bigint(21) NOT NULL,
+`maximum_value` bigint(21) NOT NULL,
+`start_value` bigint(21) NOT NULL COMMENT 'start value when sequences is created or value if RESTART is used',
+`increment` bigint(21) NOT NULL COMMENT 'increment value',
+`cache_size` bigint(21) unsigned NOT NULL,
+`cycle_option` tinyint(1) unsigned NOT NULL COMMENT '0 if no cycles are allowed, 1 if the sequence should begin a new cycle when maximum_value is passed',
+`cycle_count` bigint(21) NOT NULL COMMENT 'How many cycles have been done'
+) ENGINE=innodb;
+
+--error ER_SEQUENCE_TABLE_HAS_TOO_FEW_ROWS
+alter table s1 sequence=1;
+# (for coverage) alter a non sequence table with sequence=0
+alter table s1 sequence=0;
+insert into s1 values (1,1,9223372036854775806,1,1,1000,0,0);
+alter table s1 sequence=1;
+
+alter table s1 sequence=0;
+insert into s1 values (2,1,9223372036854775806,1,1,1000,0,0);
+--error ER_SEQUENCE_TABLE_HAS_TOO_MANY_ROWS
+alter table s1 sequence=1;
+
+# (for coverage) alter a non sequence table with sequence=0
+alter table s1 sequence=0;
+insert into s1 values (3,1,9223372036854775806,1,1,1000,0,0);
+--error ER_SEQUENCE_TABLE_HAS_TOO_MANY_ROWS
+alter table s1 sequence=1;
+
+drop table s1;
+
+--echo # End of 10.11 tests
+
 --echo #
 --echo # MDEV-28152 Features for sequence
 --echo #
diff --git a/sql/handler.cc b/sql/handler.cc
@@ -5777,6 +5777,9 @@ handler::check_if_supported_inplace_alter(TABLE *altered_table,
       (table->s->row_type != create_info->row_type))
     DBUG_RETURN(HA_ALTER_INPLACE_NOT_SUPPORTED);
 
+  if (create_info->sequence)
+    DBUG_RETURN(HA_ALTER_INPLACE_NOT_SUPPORTED);
+
   uint table_changes= (ha_alter_info->handler_flags &
                        ALTER_COLUMN_TYPE_CHANGE_BY_ENGINE) ?
     IS_EQUAL_PACK_LENGTH : IS_EQUAL_YES;
diff --git a/sql/sql_table.cc b/sql/sql_table.cc
@@ -12588,6 +12588,16 @@ copy_data_between_tables(THD *thd, TABLE *from, TABLE *to,
   copy_end=copy;
   to->s->default_fields= 0;
   error= 1;
+  if (to->s->table_type == TABLE_TYPE_SEQUENCE &&
+      from->file->ha_table_flags() & HA_STATS_RECORDS_IS_EXACT &&
+      from->file->stats.records != 1)
+  {
+    if (from->file->stats.records > 1)
+      my_error(ER_SEQUENCE_TABLE_HAS_TOO_MANY_ROWS, MYF(0));
+    else
+      my_error(ER_SEQUENCE_TABLE_HAS_TOO_FEW_ROWS, MYF(0));
+    goto err;
+  }
   for (Field **ptr=to->field ; *ptr ; ptr++)
   {
     def=it++;
@@ -12798,6 +12808,12 @@ copy_data_between_tables(THD *thd, TABLE *from, TABLE *to,
         else
           to->next_number_field->reset();
       }
+      if (to->s->table_type == TABLE_TYPE_SEQUENCE && found_count == 1)
+      {
+        my_error(ER_SEQUENCE_TABLE_HAS_TOO_MANY_ROWS, MYF(0));
+        error= 1;
+        break;
+      }
       error= to->file->ha_write_row(to->record[0]);
       to->auto_increment_field_not_null= FALSE;
       if (unlikely(error))
@@ -12869,6 +12885,11 @@ copy_data_between_tables(THD *thd, TABLE *from, TABLE *to,
 
   DEBUG_SYNC(thd, "alter_table_copy_end");
 
+  if (to->s->table_type == TABLE_TYPE_SEQUENCE && found_count == 0)
+  {
+    my_error(ER_SEQUENCE_TABLE_HAS_TOO_FEW_ROWS, MYF(0));
+    error= 1;
+  }
   THD_STAGE_INFO(thd, stage_enabling_keys);
   thd_progress_next_stage(thd);
 
