Function FormPartitionKeyDatum

src/backend/executor/execPartition.c:1257–1312

---------------- * FormPartitionKeyDatum * Construct values[] and isnull[] arrays for the partition key * of a tuple. * * pd Partition dispatch object of the partitioned table * slot Heap tuple from which to extract partition key * estate executor state for evaluating any partition key * expressions (must be non-NULL) * values Array of partition key Datums (output area)

 * ----------------
 */
static void
FormPartitionKeyDatum(PartitionDispatch pd,
					  TupleTableSlot *slot,
					  EState *estate,
					  Datum *values,
					  bool *isnull,
					  AttrMap *attno_map)
{
	ListCell   *partexpr_item;
	int			i;

	if (pd->key->partexprs != NIL && pd->keystate == NIL)
	{
		/* Check caller has set up context correctly */
		Assert(estate != NULL &&
			   GetPerTupleExprContext(estate)->ecxt_scantuple == slot);

		/* First time through, set up expression evaluation state */
		pd->keystate = ExecPrepareExprList(pd->key->partexprs, estate);
	}

	partexpr_item = list_head(pd->keystate);
	for (i = 0; i < pd->key->partnatts; i++)
	{
		AttrNumber	keycol = pd->key->partattrs[i];
		/* Use passed in map to extract part key, as slot's attrs may not match the Relation's attrs */
		if (attno_map) {
			Assert(pd->key->partattrs[i] - 1 < attno_map->maplen);
			keycol = attno_map->attnums[pd->key->partattrs[i] - 1];
		}

		Datum		datum;
		bool		isNull;

		if (keycol != 0)
		{
			/* Plain column; get the value directly from the heap tuple */
			datum = slot_getattr(slot, keycol, &isNull);
		}
		else
		{
			/* Expression; need to evaluate it */
			if (partexpr_item == NULL)
				elog(ERROR, "wrong number of partition key expressions");
			datum = ExecEvalExprSwitchContext((ExprState *) lfirst(partexpr_item),
											  GetPerTupleExprContext(estate),
											  &isNull);
			partexpr_item = lnext(pd->keystate, partexpr_item);
		}
		values[i] = datum;
		isnull[i] = isNull;
	}

	if (partexpr_item != NULL)
		elog(ERROR, "wrong number of partition key expressions");
}

/*