This topic describes GiST indexing. You can create a GiST index on a column that stores trajectory data.

Syntax

CREATE INDEX [index_name] on table_name USING GIST(traj_col [operator_family]);
  • index_name: the name of the index. This parameter is optional.
  • table_name: the name of the table to which the column belongs.
  • traj_col: the name of the column.
  • operator_family: the operator family that is used to create the index. Default value: trajgist_ops_multi. You can use the ganos.trajectory.index_split_config parameter to specify the operator family. This parameter is optional.
Note You can use the index that you create to accelerate the queries that are run by various operators and the following functions: ST_ndIntersect, ST_ndDWithin, ST_ndContains, and ST_ndWithin.

Supported operator families

The following table describes the operator families that are supported for GiST indexing.

Operator family Description
trajgist_ops_z Creates an index on the z axis. This type of index supports queries that cover only the z axis.
trajgist_ops_t Creates an index on the t axis. This type of index supports queries that cover only the t axis.
trajgist_ops_2d Creates an index on the x and y axes. This type of index supports queries that cover only the x and y axes.
trajgist_ops_2dt Creates an index on the x, y, and t axes. This type of index supports queries that cover only the x and y axes, queries that cover only the t axis, and queries that cover the x, y, and t axes.
trajgist_ops_3d Creates an index on the x, y, and z axes. This type of index supports queries that cover only the x and y axes, queries that cover only the z axis, and queries that cover the x, y, and z axes.
trajgist_ops_3dt Creates an index on the x, y, z, and t axes. This type of index supports all queries that are supported by the preceding five operator families.
trajgist_ops_multi Creates an index on multiple bounding boxes to accelerate queries. However, the system requires more time and storage to create the index.

Examples

  • Create an index on the t axis. 
    CREATE INDEX on table_name USING GIST(traj_col trajgist_ops_t);
  • Create an index on the x and y axes. 
    CREATE INDEX on table_name USING GIST(traj_col trajgist_ops_2d);
  • Create an index on the x, y, and t axes. 
    CREATE INDEX on table_name USING GIST(traj_col trajgist_ops_2dt);