greenplumn tablesample 源码
greenplumn tablesample 代码
文件路径：/src/backend/access/tablesample/tablesample.c
/*-------------------------------------------------------------------------
*
* tablesample.c
* Support functions for TABLESAMPLE feature
*
* Portions Copyright (c) 1996-2019, 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;
}
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