InnoDB Online DDL Operations with the INSTANT Alter Algorithm

Discover the INSTANT algorithm, which modifies table metadata without rebuilding the table, enabling extremely fast schema changes like adding columns.

Column Operations

ALTER TABLE ... ADD COLUMN

In MariaDB 10.3.2 and later, InnoDB supports adding columns to a table with ALGORITHM set to INSTANT if the new column is the last column in the table. See MDEV-11369 for more information. If the table has a hidden FTS_DOC_ID column is present, then this is not supported.

In MariaDB 10.4 and later, InnoDB supports adding columns to a table with ALGORITHM set to INSTANT, regardless of where in the column list the new column is added.

When this operation is performed with ALGORITHM set to INSTANT, the tablespace file will have a non-canonical storage format. See Non-canonical Storage Format Caused by Some Operations for more information.

With the exception of adding an auto-increment column, this operation supports the non-locking strategy. This strategy can be explicitly chosen by setting the LOCK clause to NONE. When this strategy is used, all concurrent DML is permitted.

For example, this succeeds:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50)
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab ADD COLUMN c VARCHAR(50);
Query OK, 0 rows affected (0.004 sec)

And this succeeds in MariaDB 10.4 and later:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50)
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab ADD COLUMN c VARCHAR(50) AFTER a;
Query OK, 0 rows affected (0.004 sec)

This applies to ALTER TABLE ... ADD COLUMN for InnoDB tables.

See Instant ADD COLUMN for InnoDB for more information.

ALTER TABLE ... DROP COLUMN

In MariaDB 10.4 and later, InnoDB supports dropping columns from a table with ALGORITHM set to INSTANT. See MDEV-15562 for more information.

When this operation is performed with ALGORITHM set to INSTANT, the tablespace file will have a non-canonical storage format. See Non-canonical Storage Format Caused by Some Operations for more information.

This operation supports the non-locking strategy. This strategy can be explicitly chosen by setting the LOCK clause to NONE. When this strategy is used, all concurrent DML is permitted.

For example:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab DROP COLUMN c;
Query OK, 0 rows affected (0.004 sec)

This applies to ALTER TABLE ... DROP COLUMN for InnoDB tables.

ALTER TABLE ... MODIFY COLUMN

This applies to ALTER TABLE ... MODIFY COLUMN for InnoDB tables.

Reordering Columns

In MariaDB 10.4 and later, InnoDB supports reordering columns within a table with ALGORITHM set to INSTANT. See MDEV-15562 for more information.

When this operation is performed with ALGORITHM set to INSTANT, the tablespace file will have a non-canonical storage format. See Non-canonical Storage Format Caused by Some Operations for more information.

This operation supports the non-locking strategy. This strategy can be explicitly chosen by setting the LOCK clause to NONE. When this strategy is used, all concurrent DML is permitted.

For example:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab MODIFY COLUMN c VARCHAR(50) AFTER a;
Query OK, 0 rows affected (0.004 sec)

Changing the Data Type of a Column

InnoDB does not support modifying a column's data type with ALGORITHM set to INSTANT in most cases. There are some exceptions:

• InnoDB supports increasing the length of VARCHAR columns with ALGORITHM set to INSTANT, unless it would require changing the number of bytes requires to represent the column's length. A VARCHAR column that is between 0 and 255 bytes in size requires 1 byte to represent its length, while a VARCHAR column that is 256 bytes or longer requires 2 bytes to represent its length. This means that the length of a column cannot be increased with ALGORITHM set to INSTANT if the original length was less than 256 bytes, and the new length is 256 bytes or more.

• In MariaDB 10.4.3 and later, InnoDB supports increasing the length of VARCHAR columns with ALGORITHM set to INSTANT with no restrictions if the ROW_FORMAT table option is set to REDUNDANT. See MDEV-15563 for more information.

• In MariaDB 10.4.3 and later, InnoDB also supports increasing the length of VARCHAR columns with ALGORITHM set to INSTANT in a more limited manner if the ROW_FORMAT table option is set to COMPACT, DYNAMIC, or COMPRESSED. In this scenario, the following limitations apply:

  • The length can be increased with ALGORITHM set to INSTANT if the original length of the column is 127 bytes or less, and the new length of the column is 256 bytes or more.

  • The length can be increased with ALGORITHM set to INSTANT if the original length of the column is 255 bytes or less, and the new length of the column is still 255 bytes or less.

  • The length can be increased with ALGORITHM set to INSTANT if the original length of the column is 256 bytes or more, and the new length of the column is still 256 bytes or more.

  • The length can not be increased with ALGORITHM set to INSTANT if the original length was between 128 bytes and 255 bytes, and the new length is 256 bytes or more.

  • See MDEV-15563 for more information.

The supported operations in this category support the non-locking strategy. This strategy can be explicitly chosen by setting the LOCK clause to NONE. When this strategy is used, all concurrent DML is permitted.

For example, this fails:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab MODIFY COLUMN c INT;
ERROR 1846 (0A000): ALGORITHM=INSTANT is not supported. Reason: Cannot change column type INPLACE. Try ALGORITHM=COPY

But this succeeds because the original length of the column is less than 256 bytes, and the new length is still less than 256 bytes:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
) CHARACTER SET=latin1;

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab MODIFY COLUMN c VARCHAR(100);
Query OK, 0 rows affected (0.005 sec)

But this fails because the original length of the column is between 128 bytes and 255 bytes, and the new length is greater than 256 bytes:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(255)
) CHARACTER SET=latin1;

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab MODIFY COLUMN c VARCHAR(256);
ERROR 1846 (0A000): ALGORITHM=INSTANT is not supported. Reason: Cannot change column type INPLACE. Try ALGORITHM=COPY

But this succeeds in MariaDB 10.4.3 and later because the table has ROW_FORMAT=REDUNDANT:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(200)
) ROW_FORMAT=REDUNDANT;

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab MODIFY COLUMN c VARCHAR(300);
Query OK, 0 rows affected (0.004 sec)

And this succeeds in MariaDB 10.4.3 and later because the table has ROW_FORMAT=DYNAMIC and the column's original length is 127 bytes or less:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(127)
) ROW_FORMAT=DYNAMIC
  CHARACTER SET=latin1;

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab MODIFY COLUMN c VARCHAR(300);
Query OK, 0 rows affected (0.003 sec)

And this succeeds in MariaDB 10.4.3 and later because the table has ROW_FORMAT=COMPRESSED and the column's original length is 127 bytes or less:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(127)
) ROW_FORMAT=COMPRESSED
  CHARACTER SET=latin1;

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab MODIFY COLUMN c VARCHAR(300);
Query OK, 0 rows affected (0.003 sec)

But this fails even in MariaDB 10.4.3 and later because the table has ROW_FORMAT=DYNAMIC and the column's original length is between 128 bytes and 255 bytes:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(128)
) ROW_FORMAT=DYNAMIC
  CHARACTER SET=latin1;

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab MODIFY COLUMN c VARCHAR(300);
ERROR 1846 (0A000): ALGORITHM=INSTANT is not supported. Reason: Cannot change column type INPLACE. Try ALGORITHM=COPY

Changing a Column to NULL

In MariaDB 10.4.3 and later, InnoDB supports modifying a column to allow NULL values with ALGORITHM set to INSTANT if the ROW_FORMAT table option is set to REDUNDANT. See MDEV-15563 for more information.

This operation supports the non-locking strategy. This strategy can be explicitly chosen by setting the LOCK clause to NONE. When this strategy is used, all concurrent DML is permitted.

For example:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50) NOT NULL
) ROW_FORMAT=REDUNDANT;

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab MODIFY COLUMN c VARCHAR(50) NULL;
Query OK, 0 rows affected (0.004 sec)

Changing a Column to NOT NULL

InnoDB does not support modifying a column to not allow NULL values with ALGORITHM set to INSTANT.

For example:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
) ROW_FORMAT=REDUNDANT;

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab MODIFY COLUMN c VARCHAR(50) NOT NULL;
ERROR 1845 (0A000): ALGORITHM=INSTANT is not supported for this operation. Try ALGORITHM=INPLACE

Adding a New ENUM Option

InnoDB supports adding a new ENUM option to a column with ALGORITHM set to INSTANT. In order to add a new ENUM option with ALGORITHM set to INSTANT, the following requirements must be met:

• It must be added to the end of the list.

• The storage requirements must not change.

This operation supports the non-locking strategy. This strategy can be explicitly chosen by setting the LOCK clause to NONE. When this strategy is used, all concurrent DML is permitted.

For example, this succeeds:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c ENUM('red', 'green')
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab MODIFY COLUMN c ENUM('red', 'green', 'blue');
Query OK, 0 rows affected (0.002 sec)

But this fails:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c ENUM('red', 'green')
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab MODIFY COLUMN c ENUM('red', 'blue', 'green');
ERROR 1846 (0A000): ALGORITHM=INSTANT is not supported. Reason: Cannot change column type INPLACE. Try ALGORITHM=COPY

Adding a New SET Option

InnoDB supports adding a new SET option to a column with ALGORITHM set to INSTANT. In order to add a new SET option with ALGORITHM set to INSTANT, the following requirements must be met:

• It must be added to the end of the list.

• The storage requirements must not change.

This operation supports the non-locking strategy. This strategy can be explicitly chosen by setting the LOCK clause to NONE. When this strategy is used, all concurrent DML is permitted.

For example, this succeeds:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c SET('red', 'green')
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab MODIFY COLUMN c SET('red', 'green', 'blue');
Query OK, 0 rows affected (0.002 sec)

But this fails:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c SET('red', 'green')
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab MODIFY COLUMN c SET('red', 'blue', 'green');
ERROR 1846 (0A000): ALGORITHM=INSTANT is not supported. Reason: Cannot change column type INPLACE. Try ALGORITHM=COPY

Removing System Versioning from a Column

In MariaDB 10.3.8 and later, InnoDB supports removing system versioning from a column with ALGORITHM set to INSTANT. In order for this to work, the system_versioning_alter_history system variable must be set to KEEP. See MDEV-16330 for more information.

This operation supports the non-locking strategy. This strategy can be explicitly chosen by setting the LOCK clause to NONE. When this strategy is used, all concurrent DML is permitted.

For example:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50) WITH SYSTEM VERSIONING
);

SET SESSION system_versioning_alter_history='KEEP';
SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab MODIFY COLUMN c VARCHAR(50) WITHOUT SYSTEM VERSIONING;
Query OK, 0 rows affected (0.004 sec)

ALTER TABLE ... ALTER COLUMN

This applies to ALTER TABLE ... ALTER COLUMN for InnoDB tables.

Setting a Column's Default Value

InnoDB supports modifying a column's DEFAULT value with ALGORITHM set to INSTANT.

This operation supports the non-locking strategy. This strategy can be explicitly chosen by setting the LOCK clause to NONE. When this strategy is used, all concurrent DML is permitted.

For example:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab ALTER COLUMN c SET DEFAULT 'NO value explicitly provided.';
Query OK, 0 rows affected (0.003 sec)

Removing a Column's Default Value

InnoDB supports removing a column's DEFAULT value with ALGORITHM set to INSTANT.

This operation supports the non-locking strategy. This strategy can be explicitly chosen by setting the LOCK clause to NONE. When this strategy is used, all concurrent DML is permitted.

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50) DEFAULT 'NO value explicitly provided.'
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab ALTER COLUMN c DROP DEFAULT;
Query OK, 0 rows affected (0.002 sec)

ALTER TABLE ... CHANGE COLUMN

InnoDB supports renaming a column with ALGORITHM set to INSTANT, unless the column's data type or attributes changed in addition to the name.

This operation supports the non-locking strategy. This strategy can be explicitly chosen by setting the LOCK clause to NONE. When this strategy is used, all concurrent DML is permitted.

For example, this succeeds:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab CHANGE COLUMN c str VARCHAR(50);
Query OK, 0 rows affected (0.004 sec)

But this fails:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab CHANGE COLUMN c num INT;
ERROR 1846 (0A000): ALGORITHM=INSTANT is not supported. Reason: Cannot change column type INPLACE. Try ALGORITHM=COPY

This applies to ALTER TABLE ... CHANGE COLUMN for InnoDB tables.

Index Operations

ALTER TABLE ... ADD PRIMARY KEY

InnoDB does not support adding a primary key to a table with ALGORITHM set to INSTANT.

For example:

CREATE OR REPLACE TABLE tab (
   a INT,
   b VARCHAR(50),
   c VARCHAR(50)
);

SET SESSION sql_mode='STRICT_TRANS_TABLES';
SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab ADD PRIMARY KEY (a);
ERROR 1845 (0A000): ALGORITHM=INSTANT is not supported for this operation. Try ALGORITHM=INPLACE

This applies to ALTER TABLE ... ADD PRIMARY KEY for InnoDB tables.

ALTER TABLE ... DROP PRIMARY KEY

InnoDB does not support dropping a primary key with ALGORITHM set to INSTANT.

For example:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab DROP PRIMARY KEY;
ERROR 1846 (0A000): ALGORITHM=INSTANT is not supported. Reason: Dropping a primary key is not allowed without also adding a new primary key. Try ALGORITHM=COPY

This applies to ALTER TABLE ... DROP PRIMARY KEY for InnoDB tables.

ALTER TABLE ... ADD INDEX and CREATE INDEX

This applies to ALTER TABLE ... ADD INDEX and CREATE INDEX for InnoDB tables.

Adding a Plain Index

InnoDB does not support adding a plain index to a table with ALGORITHM set to INSTANT.

For example, this fails:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab ADD INDEX b_index (b);
ERROR 1846 (0A000): ALGORITHM=INSTANT is not supported. Reason: ADD INDEX. Try ALGORITHM=NOCOPY

And this fails:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
);

SET SESSION alter_algorithm='INSTANT';
CREATE INDEX b_index ON tab (b);
ERROR 1846 (0A000): ALGORITHM=INSTANT is not supported. Reason: ADD INDEX. Try ALGORITHM=NOCOPY

Adding a Fulltext Index

InnoDB does not support adding a FULLTEXT index to a table with ALGORITHM set to INSTANT.

For example, this fails:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
);

SET SESSION alter_algorithm='INPLACE';
ALTER TABLE tab ADD FULLTEXT INDEX b_index (b);
Query OK, 0 rows affected (0.042 sec)

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab ADD FULLTEXT INDEX c_index (c);
ERROR 1846 (0A000): ALGORITHM=INSTANT is not supported. Reason: ADD INDEX. Try ALGORITHM=NOCOPY

And this fails:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
);

SET SESSION alter_algorithm='INPLACE';
CREATE FULLTEXT INDEX b_index ON tab (b);
Query OK, 0 rows affected (0.040 sec)

SET SESSION alter_algorithm='INSTANT';
CREATE FULLTEXT INDEX c_index ON tab (c);
ERROR 1846 (0A000): ALGORITHM=INSTANT is not supported. Reason: ADD INDEX. Try ALGORITHM=NOCOPY

Adding a Spatial Index

InnoDB does not support adding a SPATIAL index to a table with ALGORITHM set to INSTANT.

For example, this fails:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c GEOMETRY NOT NULL
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab ADD SPATIAL INDEX c_index (c);
ERROR 1846 (0A000): ALGORITHM=INSTANT is not supported. Reason: ADD INDEX. Try ALGORITHM=NOCOPY

And this fails:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c GEOMETRY NOT NULL
);

SET SESSION alter_algorithm='INSTANT';
CREATE SPATIAL INDEX c_index ON tab (c);
ERROR 1846 (0A000): ALGORITHM=INSTANT is not supported. Reason: ADD INDEX. Try ALGORITHM=NOCOPY

ALTER TABLE ... ADD FOREIGN KEY

InnoDB does not support adding foreign key constraints to a table with ALGORITHM set to INSTANT.

For example:

CREATE OR REPLACE TABLE tab1 (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50),
   d INT
);

CREATE OR REPLACE TABLE tab2 (
   a INT PRIMARY KEY,
   b VARCHAR(50)
);

SET SESSION foreign_key_checks=OFF;
SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab1 ADD FOREIGN KEY tab2_fk (d) REFERENCES tab2 (a);
ERROR 1846 (0A000): ALGORITHM=INSTANT is not supported. Reason: ADD INDEX. Try ALGORITHM=NOCOPY

This applies to ALTER TABLE ... ADD FOREIGN KEY for InnoDB tables.

ALTER TABLE ... DROP FOREIGN KEY

InnoDB supports dropping foreign key constraints from a table with ALGORITHM set to INSTANT.

This operation supports the non-locking strategy. This strategy can be explicitly chosen by setting the LOCK clause to NONE. When this strategy is used, all concurrent DML is permitted.

For example:

CREATE OR REPLACE TABLE tab2 (
   a INT PRIMARY KEY,
   b VARCHAR(50)
);

CREATE OR REPLACE TABLE tab1 (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50),
   d INT,
   FOREIGN KEY tab2_fk (d) REFERENCES tab2 (a)
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab1 DROP FOREIGN KEY tab2_fk; 
Query OK, 0 rows affected (0.004 sec)

This applies to ALTER TABLE ... DROP FOREIGN KEY for InnoDB tables.

Table Operations

ALTER TABLE ... AUTO_INCREMENT=...

InnoDB supports changing a table's AUTO_INCREMENT value with ALGORITHM set to INSTANT.

This operation supports the non-locking strategy. This strategy can be explicitly chosen by setting the LOCK clause to NONE. When this strategy is used, all concurrent DML is permitted.

For example:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab AUTO_INCREMENT=100;
Query OK, 0 rows affected (0.002 sec)

This applies to ALTER TABLE ... AUTO_INCREMENT=... for InnoDB tables.

ALTER TABLE ... ROW_FORMAT=...

InnoDB does not support changing a table's row format with ALGORITHM set to INSTANT.

For example:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
) ROW_FORMAT=DYNAMIC;

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab ROW_FORMAT=COMPRESSED;
ERROR 1846 (0A000): ALGORITHM=INSTANT is not supported. Reason: Changing table options requires the table to be rebuilt. Try ALGORITHM=INPLACE

This applies to ALTER TABLE ... ROW_FORMAT=... for InnoDB tables.

ALTER TABLE ... KEY_BLOCK_SIZE=...

InnoDB does not support changing a table's KEY_BLOCK_SIZE with ALGORITHM set to INSTANT.

For example:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
) ROW_FORMAT=COMPRESSED
  KEY_BLOCK_SIZE=4;

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab KEY_BLOCK_SIZE=2;
ERROR 1846 (0A000): ALGORITHM=INSTANT is not supported. Reason: Changing table options requires the table to be rebuilt. Try ALGORITHM=INPLACE

This applies to KEY_BLOCK_SIZE=... for InnoDB tables.

ALTER TABLE ... PAGE_COMPRESSED=1 and ALTER TABLE ... PAGE_COMPRESSION_LEVEL=...

In MariaDB 10.3.10 and later, InnoDB supports setting a table's PAGE_COMPRESSED value to 1 with ALGORITHM set to INSTANT. InnoDB does not support changing a table's PAGE_COMPRESSED value from 1 to 0 with ALGORITHM set to INSTANT.

In these versions, InnoDB also supports changing a table's PAGE_COMPRESSION_LEVEL value with ALGORITHM set to INSTANT.

This operation supports the non-locking strategy. This strategy can be explicitly chosen by setting the LOCK clause to NONE. When this strategy is used, all concurrent DML is permitted.

See MDEV-16328 for more information.

For example, this succeeds:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab PAGE_COMPRESSED=1;
Query OK, 0 rows affected (0.004 sec)

And this succeeds:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
) PAGE_COMPRESSED=1
  PAGE_COMPRESSION_LEVEL=5;

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab PAGE_COMPRESSION_LEVEL=4;
Query OK, 0 rows affected (0.004 sec)

But this fails:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
) PAGE_COMPRESSED=1;

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab PAGE_COMPRESSED=0;
ERROR 1846 (0A000): ALGORITHM=INSTANT is not supported. Reason: Changing table options requires the table to be rebuilt. Try ALGORITHM=INPLACE

This applies to ALTER TABLE ... PAGE_COMPRESSED=... and ALTER TABLE ... PAGE_COMPRESSION_LEVEL=... for InnoDB tables.

ALTER TABLE ... DROP SYSTEM VERSIONING

InnoDB does not support dropping system versioning from a table with ALGORITHM set to INSTANT.

For example:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
) WITH SYSTEM VERSIONING;

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab DROP SYSTEM VERSIONING;
ERROR 1845 (0A000): ALGORITHM=INSTANT is not supported for this operation. Try ALGORITHM=INPLACE

This applies to ALTER TABLE ... DROP SYSTEM VERSIONING for InnoDB tables.

ALTER TABLE ... DROP CONSTRAINT

In MariaDB 10.3.6 and later, InnoDB supports dropping a CHECK constraint from a table with ALGORITHM set to INSTANT. See MDEV-16331 for more information.

This operation supports the non-locking strategy. This strategy can be explicitly chosen by setting the LOCK clause to NONE. When this strategy is used, all concurrent DML is permitted.

For example:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50),
   CONSTRAINT b_not_empty CHECK (b != '')
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab DROP CONSTRAINT b_not_empty;
Query OK, 0 rows affected (0.002 sec)

This applies to ALTER TABLE ... DROP CONSTRAINT for InnoDB tables.

ALTER TABLE ... FORCE

InnoDB does not support forcing a table rebuild with ALGORITHM set to INSTANT.

For example:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab FORCE;
ERROR 1845 (0A000): ALGORITHM=INSTANT is not supported for this operation. Try ALGORITHM=INPLACE

This applies to ALTER TABLE ... FORCE for InnoDB tables.

ALTER TABLE ... ENGINE=InnoDB

InnoDB does not support forcing a table rebuild with ALGORITHM set to INSTANT.

For example:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab ENGINE=InnoDB;
ERROR 1845 (0A000): ALGORITHM=INSTANT is not supported for this operation. Try ALGORITHM=INPLACE

This applies to ALTER TABLE ... ENGINE=InnoDB for InnoDB tables.

OPTIMIZE TABLE ...

InnoDB does not support optimizing a table with ALGORITHM set to INSTANT.

For example:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
);

SHOW GLOBAL VARIABLES WHERE Variable_name IN('innodb_defragment', 'innodb_optimize_fulltext_only');
+-------------------------------+-------+
| Variable_name                 | Value |
+-------------------------------+-------+
| innodb_defragment             | OFF   |
| innodb_optimize_fulltext_only | OFF   |
+-------------------------------+-------+
2 rows in set (0.001 sec)

SET SESSION alter_algorithm='INSTANT';
OPTIMIZE TABLE tab;
+---------+----------+----------+------------------------------------------------------------------------------+
| Table   | Op       | Msg_type | Msg_text                                                                     |
+---------+----------+----------+------------------------------------------------------------------------------+
| db1.tab | optimize | note     | Table does not support optimize, doing recreate + analyze instead            |
| db1.tab | optimize | error    | ALGORITHM=INSTANT is not supported for this operation. Try ALGORITHM=INPLACE |
| db1.tab | optimize | status   | Operation failed                                                             |
+---------+----------+----------+------------------------------------------------------------------------------+
3 rows in set, 1 warning (0.002 sec)

This applies to OPTIMIZE TABLE for InnoDB tables.

ALTER TABLE ... RENAME TO and RENAME TABLE ...

InnoDB supports renaming a table with ALGORITHM set to INSTANT.

This operation supports the exclusive locking strategy. This strategy can be explicitly chosen by setting the LOCK clause to EXCLUSIVE. When this strategy is used, concurrent DML is not permitted.

For example, this succeeds:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
);

SET SESSION alter_algorithm='INSTANT';
ALTER TABLE tab RENAME TO old_tab;
Query OK, 0 rows affected (0.008 sec)

And this succeeds:

CREATE OR REPLACE TABLE tab (
   a INT PRIMARY KEY,
   b VARCHAR(50),
   c VARCHAR(50)
);

SET SESSION alter_algorithm='INSTANT';
RENAME TABLE tab TO old_tab;
Query OK, 0 rows affected (0.008 sec)

This applies to ALTER TABLE ... RENAME TO and RENAME TABLE for InnoDB tables.

Limitations

Limitations Related to Generated (Virtual and Persistent/Stored) Columns

Generated columns do not currently support online DDL for all of the same operations that are supported for "real" columns.

See Generated (Virtual and Persistent/Stored) Columns: Statement Support for more information on the limitations.

Non-canonical Storage Format Caused by Some Operations

Some operations cause a table's tablespace file to use a non-canonical storage format when the INSTANT algorithm is used. The affected operations include:

• Adding a column.

• Dropping a column.

• Reordering columns.

These operations require the following non-canonical changes to the storage format:

• A hidden metadata record at the start of the clustered index is used to store each column's DEFAULT value. This makes it possible to add new columns that have default values without rebuilding the table.

• A BLOB in the hidden metadata record is used to store column mappings. This makes it possible to drop or reorder columns without rebuilding the table. This also makes it possible to add columns to any position or drop columns from any position in the table without rebuilding the table.

• If a column is dropped, old records will contain garbage in that column's former position, and new records are written with NULL values, empty strings, or dummy values.

This non-canonical storage format has the potential to incur some performance or storage overhead for all subsequent DML operations. If you notice some issues like this and you want to normalize a table's storage format to avoid this problem, then you can do so by forcing a table rebuild by executing ALTER TABLE ... FORCE with ALGORITHM set to INPLACE:

SET SESSION alter_algorithm='INPLACE';
ALTER TABLE tab FORCE;
Query OK, 0 rows affected (0.008 sec)

However, keep in mind that there are certain scenarios where you may not be able to rebuild the table with ALGORITHM set to INPLACE. See InnoDB Online DDL Operations with ALGORITHM=INPLACE: Limitations for more information on those cases. If you hit one of those scenarios, but you still want to rebuild the table, then you would have to do so with ALGORITHM set to COPY.

Known Bugs

There are some known bugs that could lead to issues when an InnoDB DDL operation is performed using the INSTANT algorithm. This algorithm will usually be chosen by default if the operation supports the algorithm.

The effect of many of these bugs is that the table seems to forget that its tablespace file is in the non-canonical storage format.

If you are concerned that a table may be affected by one of these bugs, then your best option would be to normalize the table structure. This can be done by rebuilding the table:

SET SESSION alter_algorithm='INPLACE';
ALTER TABLE tab FORCE;
Query OK, 0 rows affected (0.008 sec)

If you are concerned about these bugs, and you want to perform an operation that supports the INSTANT algorithm, but you want to avoid using that algorithm, then you can set the algorithm to INPLACE and add the FORCE keyword to the ALTER TABLE statement:

SET SESSION alter_algorithm='INPLACE';
ALTER TABLE tab ADD COLUMN c VARCHAR(50), FORCE;

Closed Bugs

• MDEV-20066: This bug could cause a table to become corrupt if a column was added instantly. It is fixed in MariaDB 10.3.18 and MariaDB 10.4.8.

• MDEV-20117: This bug could cause a table to become corrupt if a column was dropped instantly. It is fixed in MariaDB 10.4.9.

• MDEV-19743: This bug could cause a table to become corrupt during page reorganization if a column was added instantly. It is fixed in MariaDB 10.3.17 and MariaDB 10.4.7.

• MDEV-19783: This bug could cause a table to become corrupt if a column was added instantly. It is fixed in MariaDB 10.3.17 and MariaDB 10.4.7

• MDEV-20090: This bug could cause a table to become corrupt if columns were added, dropped, or reordered instantly. It is fixed in MariaDB 10.4.9.

• MDEV-18519: This bug could cause a table to become corrupt if a column was added instantly. It is fixed in MariaDB 10.6.9, MariaDB 10.7.5, MariaDB 10.8.4 and MariaDB 10.9.2.

• MDEV-18519: This bug could cause a table to become corrupt if a column was added instantly. This isn't and won't be fixed in versions less than MariaDB 10.6.

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