setrefs.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

/*-------------------------------------------------------------------------
 *
 * setrefs.c
 *	  Post-processing of a completed plan tree: fix references to subplan
 *	  vars, and compute regproc values for operators
 *
 * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/setrefs.c,v 1.117.2.1 2005/11/22 18:23:11 momjian 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/parse_expr.h"
#include "parser/parsetree.h"
#include "utils/lsyscache.h"


typedef struct
{
	Index		varno;			/* RT index of Var */
	AttrNumber	varattno;		/* attr number of Var */
	AttrNumber	resno;			/* TLE position of Var */
} tlist_vinfo;

typedef struct
{
	List	   *tlist;			/* underlying target list */
	int			num_vars;		/* number of plain Var tlist entries */
	bool		has_non_vars;	/* are there non-plain-Var entries? */
	/* array of num_vars entries: */
	tlist_vinfo vars[1];		/* VARIABLE LENGTH ARRAY */
} indexed_tlist;				/* VARIABLE LENGTH STRUCT */

typedef struct
{
	List	   *rtable;
	indexed_tlist *outer_itlist;
	indexed_tlist *inner_itlist;
	Index		acceptable_rel;
} join_references_context;

typedef struct
{
	indexed_tlist *subplan_itlist;
	Index		subvarno;
} replace_vars_with_subplan_refs_context;

static Plan *set_subqueryscan_references(SubqueryScan *plan, List *rtable);
static bool trivial_subqueryscan(SubqueryScan *plan);
static void adjust_plan_varnos(Plan *plan, int rtoffset);
static void adjust_expr_varnos(Node *node, int rtoffset);
static bool adjust_expr_varnos_walker(Node *node, int *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_inner_join_references(Plan *inner_plan,
						  List *rtable,
						  indexed_tlist *outer_itlist);
static void set_uppernode_references(Plan *plan, Index subvarno);
static indexed_tlist *build_tlist_index(List *tlist);
static Var *search_indexed_tlist_for_var(Var *var,
							 indexed_tlist *itlist,
							 Index newvarno);
static Var *search_indexed_tlist_for_non_var(Node *node,
								 indexed_tlist *itlist,
								 Index newvarno);
static List *join_references(List *clauses,
				List *rtable,
				indexed_tlist *outer_itlist,
				indexed_tlist *inner_itlist,
				Index acceptable_rel);
static Node *join_references_mutator(Node *node,
						join_references_context *context);
static Node *replace_vars_with_subplan_refs(Node *node,
							   indexed_tlist *subplan_itlist,
							   Index subvarno);
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).
 *
 * We also perform one final optimization step, which is to delete
 * SubqueryScan plan nodes that aren't doing anything useful (ie, have
 * no qual and a no-op targetlist).  The reason for doing this last is that
 * it can't readily be done before set_plan_references, because it would
 * break set_uppernode_references: the Vars in the subquery's top tlist
 * won't match up with the Vars in the outer plan tree.  The SubqueryScan
 * serves a necessary function as a buffer between outer query and subquery
 * variable numbering ... but the executor doesn't care about that, only the
 * planner.
 *
 * set_plan_references recursively traverses the whole plan tree.
 *
 * The return value is normally the same Plan node passed in, but can be
 * different when the passed-in Plan is a SubqueryScan we decide isn't needed.
 *
 * Note: to delete a SubqueryScan, we have to renumber Vars in its child nodes
 * and append the modified subquery rangetable to the outer rangetable.
 * Therefore "rtable" is an in/out argument and really should be declared
 * "List **".  But in the interest of notational simplicity we don't do that.
 * (Since rtable can't be NIL if there's a SubqueryScan, the list header
 * address won't change when we append a subquery rangetable.)
 */
Plan *
set_plan_references(Plan *plan, List *rtable)
{
	ListCell   *l;

	if (plan == NULL)
		return NULL;

	/*
	 * 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)->indexqual);
			fix_expr_references(plan,
								(Node *) ((IndexScan *) plan)->indexqualorig);
			break;
		case T_BitmapIndexScan:
			/* no need to fix targetlist and qual */
			Assert(plan->targetlist == NIL);
			Assert(plan->qual == NIL);
			fix_expr_references(plan,
							 (Node *) ((BitmapIndexScan *) plan)->indexqual);
			fix_expr_references(plan,
						 (Node *) ((BitmapIndexScan *) plan)->indexqualorig);
			break;
		case T_BitmapHeapScan:
			fix_expr_references(plan, (Node *) plan->targetlist);
			fix_expr_references(plan, (Node *) plan->qual);
			fix_expr_references(plan,
						 (Node *) ((BitmapHeapScan *) plan)->bitmapqualorig);
			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:
			/* Needs special treatment, see comments below */
			return set_subqueryscan_references((SubqueryScan *) plan, rtable);
		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:
		case T_Material:
		case T_Sort:
		case T_Unique:
		case T_SetOp:

			/*
			 * These plan types don't actually bother to evaluate their
			 * targetlists (because they just return their unmodified input
			 * tuples).  The optimizer is lazy about creating really valid
			 * targetlists for them --- it tends to just put in a pointer to
			 * the child plan node's tlist.  Hence, we leave the tlist alone.
			 * In particular, we do not want to process subplans in the tlist,
			 * since we will likely end up reprocessing subplans that also
			 * appear in lower levels of the plan tree!
			 *
			 * Since these plan types don't check quals either, we should not
			 * find any qual expression attached to them.
			 */
			Assert(plan->qual == NIL);
			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.
			 */
			Assert(plan->qual == NIL);
			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 check 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.
			 */
			Assert(plan->qual == NIL);
			foreach(l, ((Append *) plan)->appendplans)
				lfirst(l) = set_plan_references((Plan *) lfirst(l), rtable);
			break;
		case T_BitmapAnd:
			/* BitmapAnd works like Append, but has no tlist */
			Assert(plan->targetlist == NIL);
			Assert(plan->qual == NIL);
			foreach(l, ((BitmapAnd *) plan)->bitmapplans)
				lfirst(l) = set_plan_references((Plan *) lfirst(l), rtable);
			break;
		case T_BitmapOr:
			/* BitmapOr works like Append, but has no tlist */
			Assert(plan->targetlist == NIL);
			Assert(plan->qual == NIL);
			foreach(l, ((BitmapOr *) plan)->bitmapplans)
				lfirst(l) = set_plan_references((Plan *) lfirst(l), 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.
	 */
	plan->lefttree = set_plan_references(plan->lefttree, rtable);
	plan->righttree = set_plan_references(plan->righttree, rtable);

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

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

	return plan;
}

/*
 * set_subqueryscan_references
 *		Do set_plan_references processing on a SubqueryScan
 *
 * We try to strip out the SubqueryScan entirely; if we can't, we have
 * to do the normal processing on it.
 */
static Plan *
set_subqueryscan_references(SubqueryScan *plan, List *rtable)
{
	Plan	   *result;
	RangeTblEntry *rte;
	ListCell   *l;

	/* First, recursively process the subplan */
	rte = rt_fetch(plan->scan.scanrelid, rtable);
	Assert(rte->rtekind == RTE_SUBQUERY);
	plan->subplan = set_plan_references(plan->subplan,
										rte->subquery->rtable);

	/*
	 * We have to process any initplans too; set_plan_references can't do it
	 * for us because of the possibility of double-processing.
	 */
	foreach(l, plan->scan.plan.initPlan)
	{
		SubPlan    *sp = (SubPlan *) lfirst(l);

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

	if (trivial_subqueryscan(plan))
	{
		/*
		 * We can omit the SubqueryScan node and just pull up the subplan. We
		 * have to merge its rtable into the outer rtable, which means
		 * adjusting varnos throughout the subtree.
		 */
		int			rtoffset = list_length(rtable);
		List	   *sub_rtable;
		ListCell   *lp,
				   *lc;

		sub_rtable = copyObject(rte->subquery->rtable);
		range_table_walker(sub_rtable,
						   adjust_expr_varnos_walker,
						   (void *) &rtoffset,
						   QTW_IGNORE_RT_SUBQUERIES);
		rtable = list_concat(rtable, sub_rtable);

		/*
		 * we have to copy the subplan to make sure there are no duplicately
		 * linked nodes in it, else adjust_plan_varnos might increment some
		 * varnos twice
		 */
		result = copyObject(plan->subplan);

		adjust_plan_varnos(result, rtoffset);

		result->initPlan = list_concat(plan->scan.plan.initPlan,
									   result->initPlan);

		/*
		 * We also have to transfer the SubqueryScan's result-column names
		 * into the subplan, else columns sent to client will be improperly
		 * labeled if this is the topmost plan level.  Copy the "source
		 * column" information too.
		 */
		forboth(lp, plan->scan.plan.targetlist, lc, result->targetlist)
		{
			TargetEntry *ptle = (TargetEntry *) lfirst(lp);
			TargetEntry *ctle = (TargetEntry *) lfirst(lc);

			ctle->resname = ptle->resname;
			ctle->resorigtbl = ptle->resorigtbl;
			ctle->resorigcol = ptle->resorigcol;
		}
	}
	else
	{
		/*
		 * Keep the SubqueryScan node.	We have to do the processing that
		 * set_plan_references would otherwise have done on it.  Notice 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.
		 */
		result = (Plan *) plan;

		fix_expr_references(result, (Node *) result->targetlist);
		fix_expr_references(result, (Node *) result->qual);
	}

	return result;
}

/*
 * trivial_subqueryscan
 *		Detect whether a SubqueryScan can be deleted from the plan tree.
 *
 * We can delete it if it has no qual to check and the targetlist just
 * regurgitates the output of the child plan.
 */
static bool
trivial_subqueryscan(SubqueryScan *plan)
{
	int			attrno;
	ListCell   *lp,
			   *lc;

	if (plan->scan.plan.qual != NIL)
		return false;

	if (list_length(plan->scan.plan.targetlist) !=
		list_length(plan->subplan->targetlist))
		return false;			/* tlists not same length */

	attrno = 1;
	forboth(lp, plan->scan.plan.targetlist, lc, plan->subplan->targetlist)
	{
		TargetEntry *ptle = (TargetEntry *) lfirst(lp);