Description

retrieves rows using a previously-created parallel retrieve cursor. You retrieve the rows in individual retrieve sessions, separate direct connections to individual segment endpoints that will serve the results for each individual segment. When you initiate a retrieve session, you must specify on the connection request. Because a retrieve session is independent of the parallel retrieve cursors or their corresponding endpoints, you can RETRIEVE from multiple endpoints in the same retrieve session.

A parallel retrieve cursor has an associated position, which is used by RETRIEVE. The cursor position can be before the first row of the query result, on any particular row of the result, or after the last row of the result.

When it is created, a parallel retrieve cursor is positioned before the first row. After retrieving some rows, the cursor is positioned on the row most recently retrieved.

If RETRIEVE runs off the end of the available rows then the cursor is left positioned after the last row.

RETRIEVE ALL always leaves the parallel retrieve cursor positioned after the last row.

Outputs

count

Retrieve the next count number of rows. count must be a positive number.

ALL

Retrieve all remaining rows.

endpoint_name

The name of the endpoint from which to retrieve the rows.

Notes

Use DECLARE ... PARALLEL RETRIEVE CURSOR to define a parallel retrieve cursor.

Parallel retrieve cursors do not support FETCH or MOVE operations.

– Create a parallel retrieve cursor:

– List the cursor endpoints:

  1. SELECT * FROM gp_endpoints WHERE cursorname='mycursor';

– Note the hostname, port, auth_token, and name associated with each endpoint.

– In another terminal window, initiate a retrieve session using a hostname, port, and auth_token returned from the previous query. For example:

– Fetch all rows from an endpoint (for example, the endpoint named prc10000001100000005):

    – Exit the retrieve session

    – Back in the original session, close the cursor and end the transaction:

    Compatibility

    RETRIEVE is a Greenplum Database extension. The SQL standard makes no provisions for parallel retrieve cursors.

    Parent topic: