Function ExecInitAppend

src/backend/executor/nodeAppend.c:109–292

---------------------------------------------------------------- * ExecInitAppend * * Begin all of the subscans of the append node. * * (This is potentially wasteful, since the entire result of the * append node may not be scanned, but this way all of the * structures get allocated in the executor's top level memory * block instead of that of the call to ExecAppend.) * -----------

 * ----------------------------------------------------------------
 */
AppendState *
ExecInitAppend(Append *node, EState *estate, int eflags)
{
	AppendState *appendstate = makeNode(AppendState);
	PlanState **appendplanstates;
	Bitmapset  *validsubplans;
	Bitmapset  *asyncplans;
	int			nplans;
	int			nasyncplans;
	int			firstvalid;
	int			i,
				j;

	/* check for unsupported flags */
	Assert(!(eflags & EXEC_FLAG_MARK));

	/*
	 * create new AppendState for our append node
	 */
	appendstate->ps.plan = (Plan *) node;
	appendstate->ps.state = estate;
	appendstate->ps.ExecProcNode = ExecAppend;

	/* Let choose_next_subplan_* function handle setting the first subplan */
	appendstate->as_whichplan = INVALID_SUBPLAN_INDEX;
	appendstate->as_syncdone = false;
	appendstate->as_begun = false;

	/* If run-time partition pruning is enabled, then set that up now */
	if (node->part_prune_info != NULL)
	{
		PartitionPruneState *prunestate;

		/* We may need an expression context to evaluate partition exprs */
		ExecAssignExprContext(estate, &appendstate->ps);

		/* Create the working data structure for pruning. */
		prunestate = ExecCreatePartitionPruneState(&appendstate->ps,
												   node->part_prune_info);
		appendstate->as_prune_state = prunestate;

		/* Perform an initial partition prune, if required. */
		if (prunestate->do_initial_prune)
		{
			/* Determine which subplans survive initial pruning */
			validsubplans = ExecFindInitialMatchingSubPlans(prunestate,
															list_length(node->appendplans));

			nplans = bms_num_members(validsubplans);
		}
		else
		{
			/* We'll need to initialize all subplans */
			nplans = list_length(node->appendplans);
			Assert(nplans > 0);
			validsubplans = bms_add_range(NULL, 0, nplans - 1);
		}