Note: The following description applies both to Postgres-XC and PostgreSQL if not described explicitly. You can read PostgreSQL as Postgres-XC except for version number, which is specific to each product.
Indexes are a common way to enhance database performance. An index allows the database server to find and retrieve specific rows much faster than it could do without an index. But indexes also add overhead to the database system as a whole, so they should be used sensibly.
Note: XCONLY: The following description applies only to Postgres-XC.
Each index is maintained locally in Coordinator and Datanode in Postgres-XC. Cross validation of index entries among Coordinators and Datanodes is not performed in the current implementation.