ALTER TABLE index_option (Transact-SQL)

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance SQL database in Microsoft Fabric

Specifies a set of options that can be applied to an index that is part of a constraint definition that is created by using ALTER TABLE.

For a complete description of index options, see CREATE INDEX.

Transact-SQL syntax conventions

Syntax

{
    PAD_INDEX = { ON | OFF }
  | FILLFACTOR = fillfactor
  | IGNORE_DUP_KEY = { ON | OFF }
  | STATISTICS_NORECOMPUTE = { ON | OFF }
  | ALLOW_ROW_LOCKS = { ON | OFF }
  | ALLOW_PAGE_LOCKS = { ON | OFF }
  | OPTIMIZE_FOR_SEQUENTIAL_KEY = { ON | OFF }
  | SORT_IN_TEMPDB = { ON | OFF }
  | MAXDOP = max_degree_of_parallelism
  | DATA_COMPRESSION = { NONE | ROW | PAGE | COLUMNSTORE | COLUMNSTORE_ARCHIVE }
      [ ON PARTITIONS ( { <partition_number_expression> | <range> }
      [ , ...n ] ) ]
  | XML_COMPRESSION = { ON | OFF }
      [ ON PARTITIONS ( { <partition_number_expression> | <range> }
      [ , ...n ] ) ]
  | ONLINE = { ON | OFF }
  | RESUMABLE = { ON | OFF }
  | MAX_DURATION = <time> [ MINUTES ]
}

<range> ::=
<partition_number_expression> TO <partition_number_expression>

<single_partition_rebuild__option> ::=
{
    SORT_IN_TEMPDB = { ON | OFF }
  | MAXDOP = max_degree_of_parallelism
  | DATA_COMPRESSION = { NONE | ROW | PAGE | COLUMNSTORE | COLUMNSTORE_ARCHIVE } }
  | ONLINE = { ON [ ( <low_priority_lock_wait> ) ] | OFF }
}

<low_priority_lock_wait>::=
{
    WAIT_AT_LOW_PRIORITY ( MAX_DURATION = <time> [ MINUTES ] ,
                           ABORT_AFTER_WAIT = { NONE | SELF | BLOCKERS } )
}

Arguments

PAD_INDEX = { ON | OFF }

Applies to: SQL Server 2008 (10.0.x) and later versions

Specifies index padding. The default is OFF.

• ON

  The percentage of free space that is specified by FILLFACTOR is applied to the intermediate-level pages of the index.

• OFF or fillfactor isn't specified

  The intermediate-level pages are filled to near capacity, leaving enough space for at least one row of the maximum size the index can have, given the set of keys on the intermediate pages.

FILLFACTOR = fillfactor

Applies to: SQL Server 2008 (10.0.x) and later versions

Specifies a percentage that indicates how full the Database Engine should make the leaf level of each index page during index creation or alteration. The value specified must be an integer value from 1 to 100. The default is 0.

Note

Fill factor values 0 and 100 are identical in all respects.

IGNORE_DUP_KEY = { ON | OFF }

Specifies the response type when an insert operation attempts to insert duplicate key values into a unique index. The IGNORE_DUP_KEY option applies only to insert operations after the index is created or rebuilt. The option has no effect when executing CREATE INDEX, ALTER INDEX, or UPDATE. The default is OFF.

• ON

  A warning message occurs when duplicate key values are inserted into a unique index. Only the rows violating the uniqueness constraint fail.

• OFF

  An error message occurs when duplicate key values are inserted into a unique index. The entire INSERT operation is rolled back.

IGNORE_DUP_KEY can't be set to ON for indexes created on a view, nonunique indexes, XML indexes, spatial indexes, and filtered indexes.

To view IGNORE_DUP_KEY, use sys.indexes.

In backward compatible syntax, WITH IGNORE_DUP_KEY is equivalent to WITH IGNORE_DUP_KEY = ON.

STATISTICS_NORECOMPUTE = { ON | OFF }

Disable or enable the automatic statistics update option, AUTO_STATISTICS_UPDATE, for the statistics related to the specified indexes. The default is OFF.

• ON

  Automatic statistics updates are disabled after the index is rebuilt.

• OFF

  Automatic statistics updates are enabled after the index is rebuilt.

To restore automatic statistics updating, set the STATISTICS_NORECOMPUTE to OFF, or execute UPDATE STATISTICS without the NORECOMPUTE clause.

Warning

If you disable automatic updating of statistics, it might prevent the Query Optimizer from picking optimal execution plans for queries that involve the table. You should use this option sparingly, and only by a qualified database administrator.

This setting doesn't prevent an automatic update with fullscan of the index-related statistics, during the rebuild operation.

ALLOW_ROW_LOCKS = { ON | OFF }

Applies to: SQL Server 2008 (10.0.x) and later versions

Specifies whether row locks are allowed. The default is ON.

• ON

  Row locks are allowed when accessing the index. The Database Engine determines when row locks are used.

• OFF

  Row locks aren't used.

ALLOW_PAGE_LOCKS = { ON | OFF }

Applies to: SQL Server 2008 (10.0.x) and later versions

Specifies whether page locks are allowed. The default is ON.

• ON

  Page locks are allowed when accessing the index. The Database Engine determines when page locks are used.

• OFF

  Page locks aren't used.

OPTIMIZE_FOR_SEQUENTIAL_KEY = { ON | OFF }

Applies to: SQL Server 2019 (15.x) and later versions

Specifies whether or not to optimize for last-page insert contention. The default is OFF. For more information, see the Sequential keys section of the CREATE INDEX article.

SORT_IN_TEMPDB = { ON | OFF }

Applies to: SQL Server 2008 (10.0.x) and later versions

Specifies whether to store sort results in tempdb. The default is OFF.

• ON

  The intermediate sort results that are used to build the index are stored in tempdb. This might reduce the time required to create an index if tempdb is on a different set of disks than the user database. However, this increases the amount of disk space that is used during the index build.

• OFF

  The intermediate sort results are stored in the same database as the index.

ONLINE = { ON | OFF }

Applies to: SQL Server 2008 (10.0.x) and later versions

Specifies whether underlying tables and associated indexes are available for queries and data modification during the index operation. The default is OFF. REBUILD can be performed as an ONLINE operation.

Note

Unique nonclustered indexes can't be created online. This includes indexes that are created due to a UNIQUE or PRIMARY KEY constraint.

• ON

  Long-term table locks aren't held during the index operation. During the main phase of the index operation, only an Intent Share (IS) lock is held on the source table. This enables queries or updates to the underlying table and indexes to proceed. At the start of the operation, a Shared (S) lock is held on the source object for a short period of time. At the end of the operation, for a short period of time, an S (Shared) lock is acquired on the source if a nonclustered index is being created; or a Sch-M (Schema Modification) lock is acquired when a clustered index is created or dropped online and when a clustered or nonclustered index is being rebuilt. Although the online index locks are short metadata locks, especially the Sch-M lock must wait for all blocking transactions to be completed on this table. During the wait time, the Sch-M lock blocks all other transactions that wait behind this lock when accessing the same table. ONLINE can't be set to ON when an index is being created on a local temporary table.

  Note

  Online index rebuild can set the low_priority_lock_wait options described later in this section. low_priority_lock_wait manages S and Sch-M lock priority during online index rebuild.

• OFF

  Table locks are applied during the index operation. This prevents all user access to the underlying table during the operation. An offline index operation that creates, rebuilds, or drops a clustered index, or rebuilds or drops a nonclustered index, acquires a Schema modification (Sch-M) lock on the table. This prevents all user access to the underlying table during the operation. An offline index operation that creates a nonclustered index acquires a Shared (S) lock on the table. This prevents updates to the underlying table but allows read operations, such as SELECT statements.

For more information, see How Online Index Operations Work.

Note

Online index operations aren't available in every edition of Microsoft SQL Server. For a list of features that are supported by the editions of SQL Server, see Editions and supported features of SQL Server 2022.

RESUMABLE = { ON | OFF}

Applies to: SQL Server 2022 (16.x) and later versions

Specifies whether an ALTER TABLE ADD CONSTRAINT operation is resumable. Add table constraint operation is resumable when ON. Add table constraint operation isn't resumable when OFF. Default is OFF. When the RESUMABLE option is set to ON, the option ONLINE = ON is required.

MAX_DURATION when used with RESUMABLE = ON (requires ONLINE = ON) indicates time (an integer value specified in minutes) that a resumable online add constraint operation is executed before being paused. If not specified, the operation continues until completion. MAXDOP is supported with RESUMABLE = ON as well.

For more information on enabling and using resumable ALTER TABLE ADD CONSTRAINT operations, see Resumable add table constraints.

MAXDOP = max_degree_of_parallelism

Applies to: SQL Server 2008 (10.0.x) and later versions

Overrides the max degree of parallelism configuration option during the index operation. For more information, see Configure the max degree of parallelism (server configuration option). Use MAXDOP to limit the number of processors used in a parallel plan execution. The maximum is 64 processors.

max_degree_of_parallelism can be:

• 1: Suppresses parallel plan generation.
• >1: Restricts the maximum number of processors used in a parallel index operation to the specified number.
• 0 (default): Uses the actual number of processors or fewer based on the current system workload.

For more information, see Configure Parallel Index Operations.

Note

Parallel index operations aren't available in every edition of Microsoft SQL Server. For a list of features that are supported by the editions of SQL Server, see Editions and supported features of SQL Server 2022.

DATA_COMPRESSION

Applies to: SQL Server 2008 (10.0.x) and later versions

Specifies the data compression option for the specified table, partition number, or range of partitions. The options are as follows:

• NONE

  Table or specified partitions aren't compressed. Applies only to rowstore tables; doesn't apply to columnstore tables.

• ROW

  Table or specified partitions are compressed by using row compression. Applies only to rowstore tables; doesn't apply to columnstore tables.

• PAGE

  Table or specified partitions are compressed by using page compression. Applies only to rowstore tables; doesn't apply to columnstore tables.

• COLUMNSTORE

  Applies to: SQL Server 2014 (12.x) and later versions

  Applies only to columnstore tables. COLUMNSTORE specifies to decompress a partition that was compressed with the COLUMNSTORE_ARCHIVE option. When the data is restored, the COLUMNSTORE index continues to be compressed with the columnstore compression that is used for all columnstore tables.

• COLUMNSTORE_ARCHIVE

  Applies to: SQL Server 2014 (12.x) and later versions

  Applies only to columnstore tables, which are tables stored with a clustered columnstore index. COLUMNSTORE_ARCHIVE further compresses the specified partition to a smaller size. This can be used for archival, or for other situations that require less storage and can afford more time for storage and retrieval

For more information about compression, see Data compression.

XML_COMPRESSION

Applies to: SQL Server 2022 (16.x) and later versions, Azure SQL Database, and Azure SQL Managed Instance.

Specifies the XML compression option for any xml data type columns in the table. The options are as follows:

• ON

  Columns using the xml data type are compressed.

• OFF

  Columns using the xml data type aren't compressed.

ON PARTITIONS ( { <partition_number_expression> | <range> } [ ,...n ] )

Applies to: SQL Server 2008 (10.0.x) and later versions

Specifies the partitions to which the DATA_COMPRESSION or XML_COMPRESSION settings apply. If the table isn't partitioned, the ON PARTITIONS argument generates an error. If the ON PARTITIONS clause isn't provided, the DATA_COMPRESSION or XML_COMPRESSION option applies to all partitions of a partitioned table.

<partition_number_expression> can be specified in the following ways:

• Provide the number a partition, for example: ON PARTITIONS (2).
• Provide the partition numbers for several individual partitions separated by commas, for example: ON PARTITIONS (1, 5).
• Provide both ranges and individual partitions, for example: ON PARTITIONS (2, 4, 6 TO 8).

<range> can be specified as partition numbers separated by the word TO, for example: ON PARTITIONS (6 TO 8).

To set different types of data compression for different partitions, specify the DATA_COMPRESSION option more than once, for example:

--For rowstore tables
REBUILD WITH
(
  DATA_COMPRESSION = NONE ON PARTITIONS (1),
  DATA_COMPRESSION = ROW ON PARTITIONS (2, 4, 6 TO 8),
  DATA_COMPRESSION = PAGE ON PARTITIONS (3, 5)
)

--For columnstore tables
REBUILD WITH
(
  DATA_COMPRESSION = COLUMNSTORE ON PARTITIONS (1, 3, 5),
  DATA_COMPRESSION = COLUMNSTORE_ARCHIVE ON PARTITIONS (2, 4, 6 TO 8)
)

<single_partition_rebuild__option>

In most cases, rebuilding an index also rebuilds all partitions of a partitioned index. The following options, when applied to a single partition, don't rebuild all partitions.

• SORT_IN_TEMPDB
• MAXDOP
• DATA_COMPRESSION
• XML_COMPRESSION

low_priority_lock_wait

Applies to: SQL Server 2014 (12.x) and later versions

A SWITCH or online index rebuild completes as soon as there are no blocking operations for this table. WAIT_AT_LOW_PRIORITY indicates that if the SWITCH or online index rebuild operation can't be completed immediately, it waits. The operation holds low priority locks, allowing other operations that hold locks conflicting with the DDL statement to proceed. Omitting the WAIT AT LOW PRIORITY option is equivalent to WAIT_AT_LOW_PRIORITY ( MAX_DURATION = 0 minutes, ABORT_AFTER_WAIT = NONE).

MAX_DURATION = time [ MINUTES ]

The wait time (an integer value specified in minutes) that the SWITCH or online index rebuild lock that must be acquired, waits when executing the DDL command. The SWITCH or online index rebuild operation attempts to complete immediately. If the operation is blocked for the MAX_DURATION time, one of the ABORT_AFTER_WAIT actions is executed. MAX_DURATION time is always in minutes, and the word MINUTES can be omitted.

ABORT_AFTER_WAIT = { NONE | SELF | BLOCKERS }

• NONE

  Continues the SWITCH or online index rebuild operation without changing the lock priority (using regular priority).

• SELF

  Exits the SWITCH or online index rebuild DDL operation currently being executed without taking any action.

• BLOCKERS

  Kills all user transactions that block currently the SWITCH or online index rebuild DDL operation so that the operation can continue.

  BLOCKERS requires the ALTER ANY CONNECTION permission.

Related content

• ALTER TABLE (Transact-SQL)
• ALTER TABLE column_constraint (Transact-SQL)
• ALTER TABLE computed_column_definition (Transact-SQL)
• ALTER TABLE table_constraint (Transact-SQL)