tablesample.c

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/*-------------------------------------------------------------------------
 *
 * tablesample.c
 *        Support functions for TABLESAMPLE feature
 *
 * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *        src/backend/access/tablesample/tablesample.c
 *
 * -------------------------------------------------------------------------
 */

#include "postgres.h"

#include "access/tsmapi.h"


/*
 * GetTsmRoutine --- get a TsmRoutine struct by invoking the handler.
 *
 * This is a convenience routine that's just meant to check for errors.
 */
TsmRoutine *
GetTsmRoutine(Oid tsmhandler)
{
    Datum       datum;
    TsmRoutine *routine;

    datum = OidFunctionCall1(tsmhandler, PointerGetDatum(NULL));
    routine = (TsmRoutine *) DatumGetPointer(datum);

    if (routine == NULL || !IsA(routine, TsmRoutine))
        elog(ERROR, "tablesample handler function %u did not return a TsmRoutine struct",
             tsmhandler);

    return routine;
}