Function CatCacheCopyKeys

src/backend/utils/cache/catcache.c:2002–2037

* Helper routine that copies the keys in the srckeys array into the dstkeys * one, guaranteeing that the datums are fully allocated in the current memory * context. */

 * context.
 */
static void
CatCacheCopyKeys(TupleDesc tupdesc, int nkeys, int *attnos,
				 Datum *srckeys, Datum *dstkeys)
{
	int			i;

	/*
	 * XXX: memory and lookup performance could possibly be improved by
	 * storing all keys in one allocation.
	 */

	for (i = 0; i < nkeys; i++)
	{
		int			attnum = attnos[i];
		Form_pg_attribute att = TupleDescAttr(tupdesc, attnum - 1);
		Datum		src = srckeys[i];
		NameData	srcname;

		/*
		 * Must be careful in case the caller passed a C string where a NAME
		 * is wanted: convert the given argument to a correctly padded NAME.
		 * Otherwise the memcpy() done by datumCopy() could fall off the end
		 * of memory.
		 */
		if (att->atttypid == NAMEOID)
		{
			namestrcpy(&srcname, DatumGetCString(src));
			src = NameGetDatum(&srcname);
		}

		dstkeys[i] = datumCopy(src,
							   att->attbyval,
							   att->attlen);
	}

}

/*
 *	PrepareToInvalidateCacheTuple()