subselect.c

关系型数据库 Postgresql 6.5.2

	{
		SubPlan	   *subplan = (SubPlan *) ((Expr *) node)->oper;
		List	   *lst;

		/* Add subplan to subplans list */
		results->subplans = lappend(results->subplans, subplan);
		/* Check extParam list for params to add to paramids */
		foreach(lst, subplan->plan->extParam)
		{
			int			paramid = lfirsti(lst);
			Var		   *var = nth(paramid, PlannerParamVar);

			/* note varlevelsup is absolute level number */
			if (var->varlevelsup < PlannerQueryLevel &&
				! intMember(paramid, results->paramids))
				results->paramids = lconsi(paramid, results->paramids);
		}
		/* XXX We do NOT allow expression_tree_walker to examine the args
		 * passed to the subplan.  Is that correct???  It's what the
		 * old code did, but it seems mighty bogus...  tgl 7/14/99
		 */
		return false;			/* don't recurse into subplan args */
	}
	return expression_tree_walker(node, finalize_primnode_walker,
								  (void *) results);
}

/* Replace correlation vars (uplevel vars) with Params. */

/* XXX should replace this with use of a generalized tree rebuilder,
 * designed along the same lines as expression_tree_walker.
 * Not done yet.
 */
Node *
SS_replace_correlation_vars(Node *expr)
{
	if (expr == NULL)
		return NULL;
	if (IsA(expr, Var))
	{
		if (((Var *) expr)->varlevelsup > 0)
			expr = (Node *) _replace_var((Var *) expr);
	}
	else if (single_node(expr))
		return expr;
	else if (IsA(expr, List))
	{
		List	   *le;

		foreach(le, (List *) expr)
			lfirst(le) = SS_replace_correlation_vars((Node *) lfirst(le));
	}
	else if (IsA(expr, Expr))
	{
		/* XXX do we need to do anything special with subplans? */
		((Expr *) expr)->args = (List *)
			SS_replace_correlation_vars((Node *) ((Expr *) expr)->args);
	}
	else if (IsA(expr, Aggref))
		((Aggref *) expr)->target = SS_replace_correlation_vars(((Aggref *) expr)->target);
	else if (IsA(expr, Iter))
		((Iter *) expr)->iterexpr = SS_replace_correlation_vars(((Iter *) expr)->iterexpr);
	else if (IsA(expr, ArrayRef))
	{
		((ArrayRef *) expr)->refupperindexpr = (List *)
			SS_replace_correlation_vars((Node *) ((ArrayRef *) expr)->refupperindexpr);
		((ArrayRef *) expr)->reflowerindexpr = (List *)
			SS_replace_correlation_vars((Node *) ((ArrayRef *) expr)->reflowerindexpr);
		((ArrayRef *) expr)->refexpr = SS_replace_correlation_vars(((ArrayRef *) expr)->refexpr);
		((ArrayRef *) expr)->refassgnexpr = SS_replace_correlation_vars(((ArrayRef *) expr)->refassgnexpr);
	}
	else if (IsA(expr, CaseExpr))
	{
		CaseExpr   *caseexpr = (CaseExpr *) expr;
		List	   *le;

		foreach(le, caseexpr->args)
		{
			CaseWhen   *when = (CaseWhen *) lfirst(le);
			Assert(IsA(when, CaseWhen));
			when->expr = SS_replace_correlation_vars(when->expr);
			when->result = SS_replace_correlation_vars(when->result);
		}
		/* caseexpr->arg should be null, but we'll check it anyway */
		caseexpr->arg = SS_replace_correlation_vars(caseexpr->arg);
		caseexpr->defresult = SS_replace_correlation_vars(caseexpr->defresult);
	}
	else if (IsA(expr, TargetEntry))
		((TargetEntry *) expr)->expr = SS_replace_correlation_vars(((TargetEntry *) expr)->expr);
	else if (IsA(expr, SubLink))
	{
		List	   *le;

		foreach(le, ((SubLink *) expr)->oper)	/* left sides only */
		{
			List	   *oparg = ((Expr *) lfirst(le))->args;

			lfirst(oparg) = (List *)
				SS_replace_correlation_vars((Node *) lfirst(oparg));
		}
		((SubLink *) expr)->lefthand = (List *)
			SS_replace_correlation_vars((Node *) ((SubLink *) expr)->lefthand);
	}
	else
		elog(ERROR, "SS_replace_correlation_vars: can't handle node %d",
			 nodeTag(expr));

	return expr;
}

/* Replace sublinks by subplans in the given expression */

/* XXX should replace this with use of a generalized tree rebuilder,
 * designed along the same lines as expression_tree_walker.
 * Not done yet.
 */
Node *
SS_process_sublinks(Node *expr)
{
	if (expr == NULL)
		return NULL;
	if (IsA(expr, SubLink))
	{
		expr = _make_subplan((SubLink *) expr);
	}
	else if (single_node(expr))
		return expr;
	else if (IsA(expr, List))
	{
		List	   *le;

		foreach(le, (List *) expr)
			lfirst(le) = SS_process_sublinks((Node *) lfirst(le));
	}
	else if (IsA(expr, Expr))
	{
		/* We should never see a subplan node here, since this is the
		 * routine that makes 'em in the first place.  No need to check.
		 */
		((Expr *) expr)->args = (List *)
			SS_process_sublinks((Node *) ((Expr *) expr)->args);
	}
	else if (IsA(expr, Aggref))
		((Aggref *) expr)->target = SS_process_sublinks(((Aggref *) expr)->target);
	else if (IsA(expr, Iter))
		((Iter *) expr)->iterexpr = SS_process_sublinks(((Iter *) expr)->iterexpr);
	else if (IsA(expr, ArrayRef))
	{
		((ArrayRef *) expr)->refupperindexpr = (List *)
			SS_process_sublinks((Node *) ((ArrayRef *) expr)->refupperindexpr);
		((ArrayRef *) expr)->reflowerindexpr = (List *)
			SS_process_sublinks((Node *) ((ArrayRef *) expr)->reflowerindexpr);
		((ArrayRef *) expr)->refexpr = SS_process_sublinks(((ArrayRef *) expr)->refexpr);
		((ArrayRef *) expr)->refassgnexpr = SS_process_sublinks(((ArrayRef *) expr)->refassgnexpr);
	}
	else if (IsA(expr, CaseExpr))
	{
		CaseExpr   *caseexpr = (CaseExpr *) expr;
		List	   *le;

		foreach(le, caseexpr->args)
		{
			CaseWhen   *when = (CaseWhen *) lfirst(le);
			Assert(IsA(when, CaseWhen));
			when->expr = SS_process_sublinks(when->expr);
			when->result = SS_process_sublinks(when->result);
		}
		/* caseexpr->arg should be null, but we'll check it anyway */
		caseexpr->arg = SS_process_sublinks(caseexpr->arg);
		caseexpr->defresult = SS_process_sublinks(caseexpr->defresult);
	}
	else
		elog(ERROR, "SS_process_sublinks: can't handle node %d",
			 nodeTag(expr));

	return expr;
}

List *
SS_finalize_plan(Plan *plan)
{
	List	   *extParam = NIL;
	List	   *locParam = NIL;
	finalize_primnode_results results;
	List	   *lst;

	if (plan == NULL)
		return NULL;

	/* Find params in targetlist, make sure there are no subplans there */
	finalize_primnode((Node *) plan->targetlist, &results);
	Assert(results.subplans == NIL);

	/* From here on, we invoke finalize_primnode_walker not finalize_primnode,
	 * so that results.paramids lists are automatically merged together and
	 * we don't have to do it the hard way.  But when recursing to self,
	 * we do have to merge the lists.  Oh well.
	 */
	switch (nodeTag(plan))
	{
		case T_Result:
			finalize_primnode_walker(((Result *) plan)->resconstantqual,
									 &results);
			/* results.subplans is NOT necessarily empty here ... */
			break;

		case T_Append:
			foreach(lst, ((Append *) plan)->appendplans)
				results.paramids = set_unioni(results.paramids,
								SS_finalize_plan((Plan *) lfirst(lst)));
			break;

		case T_IndexScan:
			finalize_primnode_walker((Node *) ((IndexScan *) plan)->indxqual,
									 &results);
			Assert(results.subplans == NIL);
			break;

		case T_MergeJoin:
			finalize_primnode_walker((Node *) ((MergeJoin *) plan)->mergeclauses,
									 &results);
			Assert(results.subplans == NIL);
			break;

		case T_HashJoin:
			finalize_primnode_walker((Node *) ((HashJoin *) plan)->hashclauses,
									 &results);
			Assert(results.subplans == NIL);
			break;

		case T_Hash:
			finalize_primnode_walker((Node *) ((Hash *) plan)->hashkey,
									 &results);
			Assert(results.subplans == NIL);
			break;

		case T_Agg:
			finalize_primnode_walker((Node *) ((Agg *) plan)->aggs,
									 &results);
			Assert(results.subplans == NIL);
			break;

		case T_SeqScan:
		case T_NestLoop:
		case T_Material:
		case T_Sort:
		case T_Unique:
		case T_Group:
			break;

		default:
			elog(ERROR, "SS_finalize_plan: node %d unsupported",
				 nodeTag(plan));
			return NULL;
	}

	finalize_primnode_walker((Node *) plan->qual, &results);
	/* subplans are OK in the qual... */

	results.paramids = set_unioni(results.paramids,
								  SS_finalize_plan(plan->lefttree));
	results.paramids = set_unioni(results.paramids,
								  SS_finalize_plan(plan->righttree));

	/* Now we have all the paramids and subplans */

	foreach(lst, results.paramids)
	{
		Var		   *var = nth(lfirsti(lst), PlannerParamVar);

		/* note varlevelsup is absolute level number */
		if (var->varlevelsup < PlannerQueryLevel)
			extParam = lappendi(extParam, lfirsti(lst));
		else if (var->varlevelsup > PlannerQueryLevel)
			elog(ERROR, "SS_finalize_plan: plan shouldn't reference subplan's variable");
		else
		{
			Assert(var->varno == 0 && var->varattno == 0);
			locParam = lappendi(locParam, lfirsti(lst));
		}
	}

	plan->extParam = extParam;
	plan->locParam = locParam;
	plan->subPlan = results.subplans;

	return results.paramids;
}

/* Construct a list of all subplans found within the given node tree */

static bool SS_pull_subplan_walker(Node *node, List **listptr);

List *
SS_pull_subplan(Node *expr)
{
	List	   *result = NIL;

	SS_pull_subplan_walker(expr, &result);
	return result;
}

static bool
SS_pull_subplan_walker(Node *node, List **listptr)
{
	if (node == NULL)
		return false;
	if (is_subplan(node))
	{
		*listptr = lappend(*listptr, ((Expr *) node)->oper);
		/* XXX original code did not examine args to subplan, is this right? */
		return false;
	}
	return expression_tree_walker(node, SS_pull_subplan_walker,
								  (void *) listptr);
}