Function ExecSort

src/backend/executor/nodeSort.c:48–195

---------------------------------------------------------------- * ExecSort * * Sorts tuples from the outer subtree of the node using tuplesort, * which saves the results in a temporary file or memory. After the * initial call, returns a tuple from the file with each call. * * Conditions: * -- none. * * Initial States: * -- the outer child is prepared to return the first tup

 * ----------------------------------------------------------------
 */
static TupleTableSlot *
ExecSort(PlanState *pstate)
{
	SortState  *node = castNode(SortState, pstate);
	EState	   *estate;
	ScanDirection dir;
	Tuplesortstate *tuplesortstate;
	TupleTableSlot *slot;

	CHECK_FOR_INTERRUPTS();

	/*
	 * get state info from node
	 */
	SO1_printf("ExecSort: %s\n",
			   "entering routine");

	estate = node->ss.ps.state;
	dir = estate->es_direction;
	tuplesortstate = (Tuplesortstate *) node->tuplesortstate;

	/*
	 * In Window node, we might need to call ExecSort again even when
	 * the last tuple in the Sort has been retrieved. Since we might
	 * eager free the tuplestore, the tuplestorestate could be NULL.
	 * We simply return NULL in this case.
	 */
	if (node->sort_Done && tuplesortstate == NULL)
	{
		return NULL;
	}

	/*
	 * If first time through, read all tuples from outer plan and pass them to
	 * tuplesort.c. Subsequent calls just fetch tuples from tuplesort.
	 */

	if (!node->sort_Done)
	{
		Sort	   *plannode = (Sort *) node->ss.ps.plan;
		PlanState  *outerNode;
		TupleDesc	tupDesc;

		SO1_printf("ExecSort: %s\n",
				   "sorting subplan");

		/*
		 * Want to scan subplan in the forward direction while creating the
		 * sorted data.
		 */
		estate->es_direction = ForwardScanDirection;

		/*
		 * Initialize tuplesort module.
		 */
		SO1_printf("ExecSort: %s\n",
				   "calling tuplesort_begin");