setrefs.c

PostgreSQL7.4.6 for Linux

/*-------------------------------------------------------------------------
 *
 * setrefs.c
 *	  Post-processing of a completed plan tree: fix references to subplan
 *	  vars, and compute regproc values for operators
 *
 * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $Header: /cvsroot/pgsql/src/backend/optimizer/plan/setrefs.c,v 1.97.4.1 2004/05/11 13:15:23 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "nodes/makefuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/planmain.h"
#include "optimizer/tlist.h"
#include "optimizer/var.h"
#include "parser/parsetree.h"
#include "utils/lsyscache.h"


typedef struct
{
	List	   *rtable;
	List	   *outer_tlist;
	List	   *inner_tlist;
	Index		acceptable_rel;
	bool		tlists_have_non_vars;
} join_references_context;

typedef struct
{
	Index		subvarno;
	List	   *subplan_targetlist;
	bool		tlist_has_non_vars;
} replace_vars_with_subplan_refs_context;

static void fix_expr_references(Plan *plan, Node *node);
static bool fix_expr_references_walker(Node *node, void *context);
static void set_join_references(Join *join, List *rtable);
static void set_uppernode_references(Plan *plan, Index subvarno);
static bool targetlist_has_non_vars(List *tlist);
static List *join_references(List *clauses,
				List *rtable,
				List *outer_tlist,
				List *inner_tlist,
				Index acceptable_rel,
				bool tlists_have_non_vars);
static Node *join_references_mutator(Node *node,
						join_references_context *context);
static Node *replace_vars_with_subplan_refs(Node *node,
							   Index subvarno,
							   List *subplan_targetlist,
							   bool tlist_has_non_vars);
static Node *replace_vars_with_subplan_refs_mutator(Node *node,
						replace_vars_with_subplan_refs_context *context);
static bool fix_opfuncids_walker(Node *node, void *context);
static void set_sa_opfuncid(ScalarArrayOpExpr *opexpr);


/*****************************************************************************
 *
 *		SUBPLAN REFERENCES
 *
 *****************************************************************************/

/*
 * set_plan_references
 *	  This is the final processing pass of the planner/optimizer.  The plan
 *	  tree is complete; we just have to adjust some representational details
 *	  for the convenience of the executor.	We update Vars in upper plan nodes
 *	  to refer to the outputs of their subplans, and we compute regproc OIDs
 *	  for operators (ie, we look up the function that implements each op).
 *
 *	  set_plan_references recursively traverses the whole plan tree.
 *
 * Returns nothing of interest, but modifies internal fields of nodes.
 */
void
set_plan_references(Plan *plan, List *rtable)
{
	List	   *pl;

	if (plan == NULL)
		return;

	/*
	 * Plan-type-specific fixes
	 */
	switch (nodeTag(plan))
	{
		case T_SeqScan:
			fix_expr_references(plan, (Node *) plan->targetlist);
			fix_expr_references(plan, (Node *) plan->qual);
			break;
		case T_IndexScan:
			fix_expr_references(plan, (Node *) plan->targetlist);
			fix_expr_references(plan, (Node *) plan->qual);
			fix_expr_references(plan,
								(Node *) ((IndexScan *) plan)->indxqual);
			fix_expr_references(plan,
							(Node *) ((IndexScan *) plan)->indxqualorig);
			break;
		case T_TidScan:
			fix_expr_references(plan, (Node *) plan->targetlist);
			fix_expr_references(plan, (Node *) plan->qual);
			fix_expr_references(plan,
								(Node *) ((TidScan *) plan)->tideval);
			break;
		case T_SubqueryScan:
			{
				RangeTblEntry *rte;

				/*
				 * We do not do set_uppernode_references() here, because a
				 * SubqueryScan will always have been created with correct
				 * references to its subplan's outputs to begin with.
				 */
				fix_expr_references(plan, (Node *) plan->targetlist);
				fix_expr_references(plan, (Node *) plan->qual);

				/* Recurse into subplan too */
				rte = rt_fetch(((SubqueryScan *) plan)->scan.scanrelid,
							   rtable);
				Assert(rte->rtekind == RTE_SUBQUERY);
				set_plan_references(((SubqueryScan *) plan)->subplan,
									rte->subquery->rtable);
			}
			break;
		case T_FunctionScan:
			{
				RangeTblEntry *rte;

				fix_expr_references(plan, (Node *) plan->targetlist);
				fix_expr_references(plan, (Node *) plan->qual);
				rte = rt_fetch(((FunctionScan *) plan)->scan.scanrelid,
							   rtable);
				Assert(rte->rtekind == RTE_FUNCTION);
				fix_expr_references(plan, rte->funcexpr);
			}
			break;
		case T_NestLoop:
			set_join_references((Join *) plan, rtable);
			fix_expr_references(plan, (Node *) plan->targetlist);
			fix_expr_references(plan, (Node *) plan->qual);
			fix_expr_references(plan, (Node *) ((Join *) plan)->joinqual);
			break;
		case T_MergeJoin:
			set_join_references((Join *) plan, rtable);
			fix_expr_references(plan, (Node *) plan->targetlist);
			fix_expr_references(plan, (Node *) plan->qual);
			fix_expr_references(plan, (Node *) ((Join *) plan)->joinqual);
			fix_expr_references(plan,
							(Node *) ((MergeJoin *) plan)->mergeclauses);
			break;
		case T_HashJoin:
			set_join_references((Join *) plan, rtable);
			fix_expr_references(plan, (Node *) plan->targetlist);
			fix_expr_references(plan, (Node *) plan->qual);
			fix_expr_references(plan, (Node *) ((Join *) plan)->joinqual);
			fix_expr_references(plan,
							  (Node *) ((HashJoin *) plan)->hashclauses);
			break;
		case T_Hash:

			/*
			 * Hash does not evaluate its targetlist or quals, so don't
			 * touch those (see comments below).  But we do need to fix
			 * its hashkeys.  The hashkeys are a little bizarre because
			 * they need to match the hashclauses of the parent HashJoin
			 * node, so we use join_references to fix them.
			 */
			((Hash *) plan)->hashkeys =
				join_references(((Hash *) plan)->hashkeys,
								rtable,
								NIL,
								plan->lefttree->targetlist,
								(Index) 0,
					targetlist_has_non_vars(plan->lefttree->targetlist));
			fix_expr_references(plan,
								(Node *) ((Hash *) plan)->hashkeys);
			break;
		case T_Material:
		case T_Sort:
		case T_Unique:
		case T_SetOp:

			/*
			 * These plan types don't actually bother to evaluate their
			 * targetlists or quals (because they just return their
			 * unmodified input tuples).  The optimizer is lazy about
			 * creating really valid targetlists for them.	Best to just
			 * leave the targetlist alone.	In particular, we do not want
			 * to process subplans for them, since we will likely end up
			 * reprocessing subplans that also appear in lower levels of
			 * the plan tree!
			 */
			break;
		case T_Limit:
			/*
			 * Like the plan types above, Limit doesn't evaluate its
			 * tlist or quals.  It does have live expressions for
			 * limit/offset, however.
			 */
			fix_expr_references(plan, ((Limit *) plan)->limitOffset);
			fix_expr_references(plan, ((Limit *) plan)->limitCount);
			break;
		case T_Agg:
		case T_Group:
			set_uppernode_references(plan, (Index) 0);
			fix_expr_references(plan, (Node *) plan->targetlist);
			fix_expr_references(plan, (Node *) plan->qual);
			break;
		case T_Result:

			/*
			 * Result may or may not have a subplan; no need to fix up
			 * subplan references if it hasn't got one...
			 *
			 * XXX why does Result use a different subvarno from Agg/Group?
			 */
			if (plan->lefttree != NULL)
				set_uppernode_references(plan, (Index) OUTER);
			fix_expr_references(plan, (Node *) plan->targetlist);
			fix_expr_references(plan, (Node *) plan->qual);
			fix_expr_references(plan, ((Result *) plan)->resconstantqual);
			break;
		case T_Append:

			/*
			 * Append, like Sort et al, doesn't actually evaluate its
			 * targetlist or quals, and we haven't bothered to give it its
			 * own tlist copy.	So, don't fix targetlist/qual. But do
			 * recurse into child plans.
			 */
			foreach(pl, ((Append *) plan)->appendplans)
				set_plan_references((Plan *) lfirst(pl), rtable);
			break;
		default:
			elog(ERROR, "unrecognized node type: %d",
				 (int) nodeTag(plan));
			break;
	}

	/*
	 * Now recurse into child plans and initplans, if any
	 *
	 * NOTE: it is essential that we recurse into child plans AFTER we set
	 * subplan references in this plan's tlist and quals.  If we did the
	 * reference-adjustments bottom-up, then we would fail to match this
	 * plan's var nodes against the already-modified nodes of the
	 * children.  Fortunately, that consideration doesn't apply to SubPlan
	 * nodes; else we'd need two passes over the expression trees.
	 */
	set_plan_references(plan->lefttree, rtable);
	set_plan_references(plan->righttree, rtable);

	foreach(pl, plan->initPlan)
	{
		SubPlan    *sp = (SubPlan *) lfirst(pl);

		Assert(IsA(sp, SubPlan));
		set_plan_references(sp->plan, sp->rtable);
	}
}

/*
 * fix_expr_references
 *	  Do final cleanup on expressions (targetlists or quals).
 *
 * This consists of looking up operator opcode info for OpExpr nodes
 * and recursively performing set_plan_references on subplans.
 *
 * The Plan argument is currently unused, but might be needed again someday.
 */
static void
fix_expr_references(Plan *plan, Node *node)
{
	/* This tree walk requires no special setup, so away we go... */
	fix_expr_references_walker(node, NULL);
}

static bool
fix_expr_references_walker(Node *node, void *context)
{
	if (node == NULL)
		return false;
	if (IsA(node, OpExpr))
		set_opfuncid((OpExpr *) node);
	else if (IsA(node, DistinctExpr))
		set_opfuncid((OpExpr *) node);	/* rely on struct equivalence */
	else if (IsA(node, ScalarArrayOpExpr))
		set_sa_opfuncid((ScalarArrayOpExpr *) node);
	else if (IsA(node, NullIfExpr))
		set_opfuncid((OpExpr *) node);	/* rely on struct equivalence */
	else if (IsA(node, SubPlan))
	{
		SubPlan    *sp = (SubPlan *) node;

		set_plan_references(sp->plan, sp->rtable);
	}
	return expression_tree_walker(node, fix_expr_references_walker, context);
}

/*
 * set_join_references
 *	  Modifies the target list and quals of a join node to reference its
 *	  subplans, by setting the varnos to OUTER or INNER and setting attno
 *	  values to the result domain number of either the corresponding outer
 *	  or inner join tuple item.
 *
 * In the case of a nestloop with inner indexscan, we will also need to
 * apply the same transformation to any outer vars appearing in the
 * quals of the child indexscan.
 *
 *	'join' is a join plan node
 *	'rtable' is the associated range table
 */
static void
set_join_references(Join *join, List *rtable)
{
	Plan	   *outer_plan = join->plan.lefttree;
	Plan	   *inner_plan = join->plan.righttree;
	List	   *outer_tlist = outer_plan->targetlist;
	List	   *inner_tlist = inner_plan->targetlist;
	bool		tlists_have_non_vars;

	tlists_have_non_vars = targetlist_has_non_vars(outer_tlist) ||
		targetlist_has_non_vars(inner_tlist);

	/* All join plans have tlist, qual, and joinqual */
	join->plan.targetlist = join_references(join->plan.targetlist,
											rtable,
											outer_tlist,
											inner_tlist,
											(Index) 0,
											tlists_have_non_vars);
	join->plan.qual = join_references(join->plan.qual,
									  rtable,
									  outer_tlist,
									  inner_tlist,
									  (Index) 0,
									  tlists_have_non_vars);
	join->joinqual = join_references(join->joinqual,
									 rtable,
									 outer_tlist,
									 inner_tlist,
									 (Index) 0,
									 tlists_have_non_vars);

	/* Now do join-type-specific stuff */
	if (IsA(join, NestLoop))
	{
		if (IsA(inner_plan, IndexScan))
		{
			/*
			 * An index is being used to reduce the number of tuples
			 * scanned in the inner relation.  If there are join clauses
			 * being used with the index, we must update their outer-rel
			 * var nodes to refer to the outer side of the join.
			 */
			IndexScan  *innerscan = (IndexScan *) inner_plan;
			List	   *indxqualorig = innerscan->indxqualorig;

			/* No work needed if indxqual refers only to its own rel... */
			if (NumRelids((Node *) indxqualorig) > 1)
			{
				Index		innerrel = innerscan->scan.scanrelid;

				/* only refs to outer vars get changed in the inner qual */
				innerscan->indxqualorig = join_references(indxqualorig,
														  rtable,
														  outer_tlist,
														  NIL,
														  innerrel,
												   tlists_have_non_vars);
				innerscan->indxqual = join_references(innerscan->indxqual,
													  rtable,
													  outer_tlist,
													  NIL,
													  innerrel,
												   tlists_have_non_vars);

				/*
				 * We must fix the inner qpqual too, if it has join
				 * clauses (this could happen if the index is lossy: some
				 * indxquals may get rechecked as qpquals).
				 */