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Bug#121124 Ignore unchanged CHECK columns for online DDL #723

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Bug#121124 Ignore unchanged CHECK columns for online DDL #723

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088fe64
Bug#121124 Ignore unchanged CHECK columns for online DDL
modasserbillah Aug 19, 2026
706e318
Bug#121124 Normalize temporal types for CHECK evaluation
modasserbillah Aug 27, 2026
36ba8c6
Bug#121124 Fix sql_table formatting
modasserbillah Sep 15, 2026
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10 changes: 10 additions & 0 deletions mysql-test/r/check_constraints.result
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Original file line number Diff line number Diff line change
Expand Up @@ -1259,6 +1259,16 @@ ERROR 0A000: ALGORITHM=INPLACE is not supported for this operation. Try ALGORITH
ALTER TABLE t1 MODIFY COLUMN f1 INT DEFAULT 20, algorithm=copy;
ERROR HY000: Check constraint 't1_chk_1' is violated.
DROP TABLE t1;
#
# Bug#121124 - An unrelated CHECK constraint on DATETIME should not
# prevent an online ENUM extension.
#
CREATE TABLE t1 (e ENUM('a','b') NOT NULL, d DATETIME(6),
CONSTRAINT ck CHECK (d IS NULL));
ALTER TABLE t1 MODIFY e ENUM('a','b','c') NOT NULL, ALGORITHM=INSTANT;
ALTER TABLE t1 MODIFY e ENUM('a','b','c','d') NOT NULL, ALGORITHM=INPLACE;
ALTER TABLE t1 MODIFY d DATETIME(6) DEFAULT NULL, ALGORITHM=INPLACE;
DROP TABLE t1;
#-----------------------------------------------------------------------
# Test case to verify check constraint with CHANGE COLUMN syntax.
#-----------------------------------------------------------------------
Expand Down
12 changes: 12 additions & 0 deletions mysql-test/t/check_constraints.test
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Original file line number Diff line number Diff line change
Expand Up @@ -789,6 +789,18 @@ ALTER TABLE t1 MODIFY COLUMN f1 INT DEFAULT 20, algorithm=copy;
DROP TABLE t1;


--echo #
--echo # Bug#121124 - An unrelated CHECK constraint on DATETIME should not
--echo # prevent an online ENUM extension.
--echo #
CREATE TABLE t1 (e ENUM('a','b') NOT NULL, d DATETIME(6),
CONSTRAINT ck CHECK (d IS NULL));
ALTER TABLE t1 MODIFY e ENUM('a','b','c') NOT NULL, ALGORITHM=INSTANT;
ALTER TABLE t1 MODIFY e ENUM('a','b','c','d') NOT NULL, ALGORITHM=INPLACE;
ALTER TABLE t1 MODIFY d DATETIME(6) DEFAULT NULL, ALGORITHM=INPLACE;
DROP TABLE t1;


--echo #-----------------------------------------------------------------------
--echo # Test case to verify check constraint with CHANGE COLUMN syntax.
--echo #-----------------------------------------------------------------------
Expand Down
11 changes: 5 additions & 6 deletions sql/sql_table.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -7580,8 +7580,7 @@ static bool prepare_key(
Create_field *sql_field;
while ((sql_field = it++) &&
my_strcasecmp(system_charset_info, first_col->get_field_name(),
sql_field->field_name))
;
sql_field->field_name));
if (!sql_field) {
my_error(ER_KEY_COLUMN_DOES_NOT_EXITS, MYF(0),
first_col->get_field_name());
Expand Down Expand Up @@ -19204,8 +19203,7 @@ bool mysql_alter_table(THD *thd, const char *new_db, const char *new_name,
mysql_rename_table(
thd, old_db_type, alter_ctx.db, backup_name, alter_ctx.db,
backup_name, *schema, alter_ctx.db, alter_ctx.alias,
FN_FROM_IS_TMP | NO_FK_CHECKS | NO_FK_RENAME | NO_CC_RENAME))
;
FN_FROM_IS_TMP | NO_FK_CHECKS | NO_FK_RENAME | NO_CC_RENAME));
}
goto err_with_mdl;
}
Expand Down Expand Up @@ -20916,9 +20914,10 @@ static bool is_any_check_constraints_evaluation_required(
continue;

// Check if data type is changed.
if (!my_strcasecmp(system_charset_info, itm_fld->field_name,
if (fld.change &&
!my_strcasecmp(system_charset_info, itm_fld->field_name,
fld.field_name) &&
(itm_fld->data_type() != fld.sql_type))
(itm_fld->data_type() != real_type_to_type(fld.sql_type)))

@RidhaOracle RidhaOracle Sep 18, 2026

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real_type_to_type function only normalizes temporal types but here we compare Field::type() with a real type fld.sql_type.

For ENUM/SET it becomes MYSQL_TYPE_STRING vs MYSQL_TYPE_ENUM``/MYSQL_TYPE_SET`.

Reproduction example:

CREATE TABLE t (
  e ENUM('a','b'),
  CONSTRAINT ck CHECK (e IS NULL OR e IN ('a','b'))
);

ALTER TABLE t
  MODIFY e ENUM('a','b') DEFAULT 'a',
 ALGORITHM=INPLACE;

The ALTER only changes the default, does not affect existing row and the CHECK does not use DEFAULT(e) but it fails with ER_ALTER_OPERATION_NOT_SUPPORTED.

Should we compare itm_fld->field->real_type() with fld.sql_type instead ?

@RidhaOracle RidhaOracle Sep 18, 2026

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Also useful too add this test as a regression test.

return true;
}

Expand Down
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