CREATE XML INDEX (Transact-SQL)

Syntax

Create XML Index 
CREATE [ PRIMARY ] XML INDEX index_name 
    ON <object> (xml_column_name )
    [ USING XML INDEX xml_index_name 
        [ FOR { VALUE | PATH | PROPERTY } ] ]
    [ WITH ( <xml_index_option> [ ,...n ] ) ]
[ ; ]

<object> ::=
{
    [ database_name. [ schema_name ] . | schema_name. ] 
    table_name
}

<xml_index_option> ::=
{ 
    PAD_INDEX  = { ON | OFF }
  | FILLFACTOR = fillfactor
  | SORT_IN_TEMPDB = { ON | OFF }
  | IGNORE_DUP_KEY =OFF
  | DROP_EXISTING = { ON | OFF }
  | ONLINE =OFF
  | ALLOW_ROW_LOCKS = { ON | OFF }
  | ALLOW_PAGE_LOCKS = { ON | OFF }
  | MAXDOP =max_degree_of_parallelism
}

Arguments

• [PRIMARY] XML
  Creates an XML index on the specified xml column. When PRIMARY is specified, a clustered index is created with the clustered key formed from the clustering key of the user table and an XML node identifier. Each table can have up to 249 XML indexes. Note the following when you create an XML index:

  • A clustered index must exist on the primary key of the user table.

  • The clustering key of the user table is limited to 15 columns.

  • Each xml column in a table can have one primary XML index and multiple secondary XML indexes.

  • A primary XML index on an xml column must exist before a secondary XML index can be created on the column.

  • An XML index can only be created on a single xml column. You cannot create an XML index on a non-xml column, nor can you create a relational index on an xml column.

  • You cannot create an XML index, either primary or secondary, on an xml column in a view, on a table-valued variable with xml columns, or xml type variables.

  • You cannot create a primary XML index on a computed xml column.

  • The SET option settings must be the same as those required for indexed views and computed column indexes. Specifically, the option ARITHABORT must be set to ON when an XML index is created and when inserting, deleting, or updating values in the xml column. For more information, see SET Options That Affect Results.

  For more information, see Indexes on XML Data Type Columns.

• index_name
  Is the name of the index. Index names must be unique within a table but do not have to be unique within a database. Index names must follow the rules of identifiers.

  Primary XML index names cannot start with the following characters: #, ##, @, or @@.

• xml_column_name
  Is the xml column on which the index is based. Only one xml column can be specified in a single XML index definition; however, multiple secondary XML indexes can be created on an xml column.

• USING XML INDEX xml_index_name
  Specifies the primary XML index to use in creating a secondary XML index.

• FOR { VALUE | PATH | PROPERTY }
  Specifies the type of secondary XML index.

  • VALUE
    Creates a secondary XML index on columns where key columns are (node value and path) of the primary XML index.

  • PATH
    Creates a secondary XML index on columns built on path values and node values in the primary XML index. In the PATH secondary index, the path and node values are key columns that allow efficient seeks when searching for paths.

  • PROPERTY
    Creates a secondary XML index on columns (PK, path and node value) of the primary XML index where PK is the primary key of the base table.

<object>::=

Is the fully qualified or nonfully qualified object to be indexed.

• database_name
  Is the name of the database.

• schema_name
  Is the name of the schema to which the table belongs.

• table_name
  Is the name of the table to be indexed.

<xml_index_option> ::=

Specifies the options to use when you create the index.

• PAD_INDEX = { ON | OFF }
  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 is not specified
    The intermediate-level pages are filled to near capacity, leaving sufficient space for at least one row of the maximum size the index can have, considering the set of keys on the intermediate pages.

  The PAD_INDEX option is useful only when FILLFACTOR is specified, because PAD_INDEX uses the percentage specified by FILLFACTOR. If the percentage specified for FILLFACTOR is not large enough to allow for one row, the Database Engine internally overrides the percentage to allow for the minimum. The number of rows on an intermediate index page is never less than two, regardless of how low the value of fillfactor.  

• FILLFACTOR **=**fillfactor
  Specifies a percentage that indicates how full the Database Engine should make the leaf level of each index page during index creation or rebuild. fillfactor must be an integer value from 1 to 100. The default is 0. If fillfactor is 100 or 0, the Database Engine creates indexes with leaf pages filled to capacity.

  Note

  Fill factor values 0 and 100 are the same in all respects.

  The FILLFACTOR setting applies only when the index is created or rebuilt. The Database Engine does not dynamically keep the specified percentage of empty space in the pages. To view the fill factor setting, use the sys.indexes catalog view.

  Important

  Creating a clustered index with a FILLFACTOR less than 100 affects the amount of storage space the data occupies because the Database Engine redistributes the data when it creates the clustered index.

  For more information, see Fill Factor.

• SORT_IN_TEMPDB = { ON | OFF }
  Specifies whether to store temporary 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 may 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.

  In addition to the space required in the user database to create the index, tempdb must have about the same amount of additional space to hold the intermediate sort results. For more information, see tempdb and Index Creation.

• IGNORE_DUP_KEY **=**OFF
  Has no effect for XML indexes because the index type is never unique. Do not set this option to ON, or else an error is raised.

• DROP_EXISTING = { ON | OFF }
  Specifies that the named, preexisting XML index is dropped and rebuilt. The default is OFF.

  • ON
    The existing index is dropped and rebuilt. The index name specified must be the same as a currently existing index; however, the index definition can be modified. For example, you can specify different columns, sort order, partition scheme, or index options.

  • OFF
    An error is displayed if the specified index name already exists.

  The index type cannot be changed by using DROP_EXISTING. Also, a primary XML index cannot be redefined as a secondary XML index, or vice versa.

• ONLINE **=**OFF
  Specifies that underlying tables and associated indexes are not available for queries and data modification during the index operation. In this version of SQL Server, online index builds are not supported for XML indexes. If this option is set to ON for a XML index, an error is raised. Either omit the ONLINE option or set ONLINE to OFF.

  An offline index operation that creates, rebuilds, or drops a XML index, acquires a Schema modification (Sch-M) lock on the table. This prevents all user access to the underlying table for the duration of the operation.

  Note

  Online index operations are available only in SQL Server Enterprise, Developer, and Evaluation editions.

• ALLOW_ROW_LOCKS = { ON | OFF }
  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 are not used.

• ALLOW_PAGE_LOCKS = { ON | OFF }
  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 are not used.

• MAXDOP **=**max_degree_of_parallelism
  Overrides the max degree of parallelism configuration option for the duration of the index operation. Use MAXDOP to limit the number of processors used in a parallel plan execution. The maximum is 64 processors.

  Important

  Although the MAXDOP option is syntactically supported for all XML indexes, for a primary XML index, CREATE XML INDEX uses only a single processor.

  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 or fewer based on the current system workload.

  • 0 (default)
    Uses the actual number of processors or fewer based on the current system workload.

  For more information, see Configuring Parallel Index Operations.

  Note

  Parallel index operations are available only in SQL Server Enterprise, Developer, and Evaluation editions.

Remarks

Computed columns derived from xml data types can be indexed either as a key or included nonkey column as long as the computed column data type is allowable as an index key column or nonkey column. You cannot create a primary XML index on a computed xml column.

To view information about XML indexes, use the sys.xml_indexes catalog view.

For more information about XML indexes, see Indexes on XML Data Type Columns.

Additional Remarks on Index Creation

Examples

A. Creating a primary XML index

USE AdventureWorks;
GO
IF EXISTS (SELECT * FROM sys.indexes
            WHERE name = N'PXML_ProductModel_CatalogDescription')
    DROP INDEX PXML_ProductModel_CatalogDescription 
        ON Production.ProductModel;
GO
CREATE PRIMARY XML INDEX PXML_ProductModel_CatalogDescription
    ON Production.ProductModel (CatalogDescription);
GO

B. Creating a secondary XML index

USE AdventureWorks;
GO
IF EXISTS (SELECT name FROM sys.indexes
            WHERE name = N'IXML_ProductModel_CatalogDescription_Path')
    DROP INDEX IXML_ProductModel_CatalogDescription_Path
        ON Production.ProductModel;
GO
CREATE XML INDEX IXML_ProductModel_CatalogDescription_Path 
    ON Production.ProductModel (CatalogDescription)
    USING XML INDEX PXML_ProductModel_CatalogDescription FOR PATH ;
GO

See Also

Reference

Concepts

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