18 SQL Statements for Indexing Spatial Data

ALTER INDEX

Purpose

Alters specific parameters for a spatial index.

Syntax

ALTER INDEX [schema.]index PARAMETERS ('index_params [physical_storage_params]' )

    [{ NOPARALLEL | PARALLEL [ integer ] }] ;

Keywords and Parameters

Prerequisites

• You must have EXECUTE privileges on the index type and its implementation type.

• The spatial index to be altered is not marked in-progress.

Usage Notes

Use this statement to change the parameters of an existing index.

See the Usage Notes for the CREATE INDEX statement for usage information about many of the other available parameters.

Examples

The following example modifies the tablespace for partition IP2 of the spatial index named BGI.

ALTER INDEX bgi MODIFY PARTITION ip2 
   PARAMETERS ('tablespace=TBS_3');

Related Topics

• ALTER INDEX REBUILD

• ALTER INDEX RENAME TO

• CREATE INDEX

• ALTER TABLE (clauses for partition maintenance) in Oracle Database SQL Language Reference

ALTER INDEX REBUILD

Syntax

ALTER INDEX [schema.]index REBUILD

     [PARAMETERS ('rebuild_params [physical_storage_params]' ) ]

     [{ NOPARALLEL | PARALLEL [ integer ] }] ;

or

ALTER INDEX [schema.]index REBUILD ONLINE

     [PARAMETERS ('rebuild_params [physical_storage_params]' ) ]

     [{ NOPARALLEL | PARALLEL [ integer ] }] ;

or

ALTER INDEX [schema.]index REBUILD PARTITION partition

     [PARAMETERS ('rebuild_params [physical_storage_params]' ) ];

Purpose

Rebuilds a spatial index or a specified partition of a partitioned index.

Keywords and Parameters

Prerequisites

• You must have EXECUTE privileges on the index type and its implementation type.

• The spatial index to be altered is not marked in-progress.

Usage Notes

An ALTER INDEX REBUILD 'rebuild_params' statement rebuilds the index using supplied parameters. Spatial index creation involves creating and inserting index data, for each row in the underlying table column being spatially indexed, into a table with a prescribed format. All rows in the underlying table are processed before the insertion of index data is committed, and this requires adequate rollback segment space.

The ONLINE keyword rebuilds the index without blocking the index; that is, queries can use the spatial index while it is being rebuilt. However, after all queries issued during the rebuild operation have completed, you must clean up the old index information (in the MDRT tables) by entering a SQL statement in the following form:

ALTER INDEX [schema.]index REBUILD ONLINE PARAMETERS ('index_status=cleanup');

The following limitations apply to the use of the ONLINE keyword:

• Only query operations are permitted while the index is being rebuilt. Insert, update, and delete operations that would affect the index are blocked while the index is being rebuilt; and an online rebuild is blocked while any insert, update, or delete operations that would affect the index are being performed.

• You cannot use the ONLINE keyword for a rebuild operation if the index was created using the 'sdo_non_leaf_tbl=TRUE' parameter.

• You cannot use the ONLINE keyword for a partitioned spatial index.

The ALTER INDEX REBUILD statement does not use any previous parameters from the index creation. All parameters should be specified for the index you want to rebuild.

For more information about using the layer_gtype keyword to constrain data in a layer to a geometry type, see Section 5.1.1.

With a partitioned spatial index, you must use a separate ALTER INDEX REBUILD statement for each partition to be rebuilt.

See also the Usage Notes for the CREATE INDEX statement for usage information about many of the available parameters and about the use of the PARALLEL keyword.

Examples

The following example rebuilds OLDINDEX and specifies the tablespace in which to create the index data table.

ALTER INDEX oldindex REBUILD PARAMETERS('tablespace=TBS_3');

Related Topics

• CREATE INDEX

• DROP INDEX

• ALTER TABLE and ALTER INDEX (clauses for partition maintenance) in Oracle Database SQL Language Reference

ALTER INDEX RENAME TO

Syntax

ALTER INDEX [schema.]index RENAME TO <new_index_name>;

ALTER INDEX [schema.]index PARTITION partition RENAME TO <new_partition_name>;

Purpose

Changes the name of a spatial index or a partition of a spatial index.

Keywords and Parameters

Prerequisites

• You must have EXECUTE privileges on the index type and its implementation type.

• The spatial index to be altered is not marked in-progress.

Usage Notes

None.

Examples

The following example renames OLDINDEX to NEWINDEX.

ALTER INDEX oldindex RENAME TO newindex;

Related Topics

• CREATE INDEX

• DROP INDEX

CREATE INDEX

Syntax

CREATE INDEX [schema.]index ON [schema.]table (column)

     INDEXTYPE IS MDSYS.SPATIAL_INDEX

     [PARAMETERS ('index_params [physical_storage_params]' )]

     [{ NOPARALLEL | PARALLEL [ integer ] }];

Purpose

Creates a spatial index on a column of type SDO_GEOMETRY.

Keywords and Parameters

Prerequisites

• All current SQL CREATE INDEX prerequisites apply.

• You must have EXECUTE privilege on the index type and its implementation type.

• The USER_SDO_GEOM_METADATA view must contain an entry with the dimensions and coordinate boundary information for the table column to be spatially indexed.

Usage Notes

For information about spatial indexes, see Section 1.7.

Before you create a spatial index, be sure that the rollback segment size and the SORT_AREA_SIZE parameter value are adequate, as described in Section 5.1.

If an R-tree index is used on linear referencing system (LRS) data and if the LRS data has four dimensions (three plus the M dimension), the sdo_indx_dims parameter must be used and must specify 3 (the number of dimensions minus one), to avoid the default sdo_indx_dims value of 2, which would index only the X and Y dimensions. For example, if the dimensions are X, Y, Z, and M, specify sdo_indx_dims=3 to index the X, Y, and Z dimensions, but not the measure (M) dimension. (The LRS data model, including the measure dimension, is explained in Section 7.2.)

A partitioned spatial index can be created on a partitioned table. See Section 5.1.3 for more information about partitioned spatial indexes, including benefits and restrictions.

A spatial index cannot be created on an index-organized table.

You can specify the PARALLEL keyword to cause the index creation to be parallelized. For example:

CREATE INDEX cola_spatial_idx ON cola_markets(shape)
   INDEXTYPE IS MDSYS.SPATIAL_INDEX PARALLEL;

For information about using the PARALLEL keyword, see the description of the parallel_clause in the section on the CREATE INDEX statement in Oracle Database SQL Language Reference. In addition, the following notes apply to the use of the PARALLEL keyword for creating or rebuilding (using the ALTER INDEX REBUILD statement) spatial indexes:

• The performance cost and benefits from parallel execution for creating or rebuilding an index depend on system resources and load. If the CPUs or disk controllers are already heavily loaded, you should not specify the PARALLEL keyword.

• Specifying PARALLEL for creating or rebuilding an index on tables with simple geometries, such as point data, usually results in less performance improvement than on tables with complex geometries.

Other options available for regular indexes (such as ASC and DESC) are not applicable for spatial indexes.

Spatial index creation involves creating and inserting index data, for each row in the underlying table column being spatially indexed, into a table with a prescribed format. All rows in the underlying table are processed before the insertion of index data is committed, and this requires adequate rollback segment space.

If a tablespace name is provided in the parameters clause, the user (underlying table owner) must have appropriate privileges for that tablespace.

For more information about using the layer_gtype keyword to constrain data in a layer to a geometry type, see Section 5.1.1.

The sdo_dml_batch_size parameter can improve application performance, because Spatial can preallocate system resources to perform multiple index updates more efficiently than successive single index updates; however, to gain the performance benefit, you must not perform commit operations after each insert operation or at intervals less than or equal to the sdo_dml_batch_size value. You should not specify a value greater than 10000 (ten thousand), because the cost of the additional memory and other resources required will probably outweigh any marginal performance increase resulting from such a value.

Specifying 'sdo_non_leaf_tbl=TRUE' can help query performance with large data sets if the entire R-tree table may not fit in the KEEP buffer pool. In this case, you must also cause Oracle to buffer the MDNT_...$ table in the KEEP buffer pool, for example, by using ALTER TABLE and specifying STORAGE (BUFFER_POOL KEEP). For partitioned indexes, the same sdo_non_leaf_tbl value must be used for all partitions. Any physical storage parameters, except for tablespace, are applied only to the MDRT_...$ table. The MDNT_...$ table uses only the tablespace parameter, if specified, and default values for all other physical storage parameters.

If you are creating a function-based spatial index, the number of parameters must not exceed 32. For information about using function-based spatial indexes, see Section 9.2.

To determine if a CREATE INDEX statement for a spatial index has failed, check to see if the DOMIDX_OPSTATUS column in the USER_INDEXES view is set to FAILED. This is different from the case of regular indexes, where you check to see if the STATUS column in the USER_INDEXES view is set to FAILED.

If the CREATE INDEX statement fails because of an invalid geometry, the ROWID of the failed geometry is returned in an error message along with the reason for the failure.

If the CREATE INDEX statement fails for any reason, then the DROP INDEX statement must be used to clean up the partially built index and associated metadata. If DROP INDEX does not work, add the FORCE parameter and try again.

Examples

The following example creates a spatial R-tree index named COLA_SPATIAL_IDX.

CREATE INDEX cola_spatial_idx ON cola_markets(shape)
   INDEXTYPE IS MDSYS.SPATIAL_INDEX;

Related Topics

• ALTER INDEX

• DROP INDEX

DROP INDEX

Syntax

DROP INDEX [schema.]index [FORCE];

Purpose

Deletes a spatial index.

Keywords and Parameters

Prerequisites

You must have EXECUTE privileges on the index type and its implementation type.

Usage Notes

Use DROP INDEX indexname FORCE to clean up after a failure in the CREATE INDEX statement.

Examples

The following example deletes a spatial index named OLDINDEX and forces the deletion to be performed even if the index is marked in-process or an error occurs.

DROP INDEX oldindex FORCE;

Related Topics

• CREATE INDEX