Function GetFdwRoutineForRelation

src/backend/foreign/foreign.c:695–726

* GetFdwRoutineForRelation - look up the handler of the foreign-data wrapper * for the given foreign table, and retrieve its FdwRoutine struct. * * This function is preferred over GetFdwRoutineByRelId because it caches * the data in the relcache entry, saving a number of catalog lookups. * * If makecopy is true then the returned data is freshly palloc'd in the * caller's memory context. Ot

 * which will be lost in any relcache reset --- so don't rely on it long.
 */
FdwRoutine *
GetFdwRoutineForRelation(Relation relation, bool makecopy)
{
	FdwRoutine *fdwroutine;
	FdwRoutine *cfdwroutine;

	if (relation->rd_fdwroutine == NULL)
	{
		/* Get the info by consulting the catalogs and the FDW code */
		fdwroutine = GetFdwRoutineByRelId(RelationGetRelid(relation));

		/* Save the data for later reuse in CacheMemoryContext */
		cfdwroutine = (FdwRoutine *) MemoryContextAlloc(CacheMemoryContext,
														sizeof(FdwRoutine));
		memcpy(cfdwroutine, fdwroutine, sizeof(FdwRoutine));
		relation->rd_fdwroutine = cfdwroutine;

		/* Give back the locally palloc'd copy regardless of makecopy */
		return fdwroutine;
	}

	/* We have valid cached data --- does the caller want a copy? */
	if (makecopy)
	{
		fdwroutine = (FdwRoutine *) palloc(sizeof(FdwRoutine));
		memcpy(fdwroutine, relation->rd_fdwroutine, sizeof(FdwRoutine));
		return fdwroutine;
	}

	/* Only a short-lived reference is needed, so just hand back cached copy */
	return relation->rd_fdwroutine;
}


/*