• Tom Lane's avatar
    Further work on making use of new statistics in planner. Adjust APIs · 7c579fa1
    Tom Lane authored
    of costsize.c routines to pass Query root, so that costsize can figure
    more things out by itself and not be so dependent on its callers to tell
    it everything it needs to know.  Use selectivity of hash or merge clause
    to estimate number of tuples processed internally in these joins
    (this is more useful than it would've been before, since eqjoinsel is
    somewhat more accurate than before).
    7c579fa1
tidpath.c 6.2 KB
/*-------------------------------------------------------------------------
 *
 * tidpath.c
 *	  Routines to determine which tids are usable for scanning a
 *	  given relation, and create TidPaths accordingly.
 *
 * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $Header: /cvsroot/pgsql/src/backend/optimizer/path/tidpath.c,v 1.9 2001/06/05 05:26:04 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
#include <math.h>

#include "postgres.h"

#include "catalog/pg_operator.h"
#include "optimizer/clauses.h"
#include "optimizer/cost.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "parser/parse_coerce.h"
#include "utils/lsyscache.h"

static void create_tidscan_joinpaths(Query *root, RelOptInfo *rel);
static List *TidqualFromRestrictinfo(List *relids, List *restrictinfo);
static bool isEvaluable(int varno, Node *node);
static Node *TidequalClause(int varno, Expr *node);
static List *TidqualFromExpr(int varno, Expr *expr);

static
bool
isEvaluable(int varno, Node *node)
{
	List	   *lst;
	Expr	   *expr;

	if (IsA(node, Const))
		return true;
	if (IsA(node, Param))
		return true;
	if (IsA(node, Var))
	{
		Var		   *var = (Var *) node;

		if (var->varno == varno)
			return false;
		return true;
	}
	if (!is_funcclause(node))
		return false;
	expr = (Expr *) node;
	foreach(lst, expr->args)
	{
		if (!isEvaluable(varno, lfirst(lst)))
			return false;
	}

	return true;
}

/*
 *	The 2nd parameter should be an opclause
 *	Extract the right node if the opclause is CTID= ....
 *	  or	the left  node if the opclause is ....=CTID
 */
static
Node *
TidequalClause(int varno, Expr *node)
{
	Node	   *rnode = 0,
			   *arg1,
			   *arg2,
			   *arg;
	Oper	   *oper;
	Var		   *var;
	Const	   *aconst;
	Param	   *param;
	Expr	   *expr;

	if (!node->oper)
		return rnode;
	if (!node->args)
		return rnode;
	if (length(node->args) != 2)
		return rnode;
	oper = (Oper *) node->oper;
	if (oper->opno != TIDEqualOperator)
		return rnode;
	arg1 = lfirst(node->args);
	arg2 = lsecond(node->args);

	arg = (Node *) 0;
	if (IsA(arg1, Var))
	{
		var = (Var *) arg1;
		if (var->varno == varno &&
			var->varattno == SelfItemPointerAttributeNumber &&
			var->vartype == TIDOID)
			arg = arg2;
		else if (var->varnoold == varno &&
				 var->varoattno == SelfItemPointerAttributeNumber &&
				 var->vartype == TIDOID)
			arg = arg2;
	}
	if ((!arg) && IsA(arg2, Var))
	{
		var = (Var *) arg2;
		if (var->varno == varno &&
			var->varattno == SelfItemPointerAttributeNumber &&
			var->vartype == TIDOID)
			arg = arg1;
	}
	if (!arg)
		return rnode;
	switch (nodeTag(arg))
	{
		case T_Const:
			aconst = (Const *) arg;
			if (aconst->consttype != TIDOID)
				return rnode;
			if (aconst->constbyval)
				return rnode;
			rnode = arg;
			break;
		case T_Param:
			param = (Param *) arg;
			if (param->paramtype != TIDOID)
				return rnode;
			rnode = arg;
			break;
		case T_Var:
			var = (Var *) arg;
			if (var->varno == varno ||
				var->vartype != TIDOID)
				return rnode;
			rnode = arg;
			break;
		case T_Expr:
			expr = (Expr *) arg;
			if (expr->typeOid != TIDOID)
				return rnode;
			if (expr->opType != FUNC_EXPR)
				return rnode;
			if (isEvaluable(varno, (Node *) expr))
				rnode = arg;
			break;
		default:
			break;
	}
	return rnode;
}

/*
 *	Extract the list of CTID values from a specified expr node.
 *	When the expr node is an or_clause,we try to extract CTID
 *	values from all member nodes. However we would discard them
 *	all if we couldn't extract CTID values from a member node.
 *	When the expr node is an and_clause,we return the list of
 *	CTID values if we could extract the CTID values from a member
 *	node.
 */
static
List *
TidqualFromExpr(int varno, Expr *expr)
{
	List	   *rlst = NIL,
			   *lst,
			   *frtn;
	Node	   *node = (Node *) expr,
			   *rnode;

	if (is_opclause(node))
	{
		rnode = TidequalClause(varno, expr);
		if (rnode)
			rlst = lcons(rnode, rlst);
	}
	else if (and_clause(node))
	{
		foreach(lst, expr->args)
		{
			node = lfirst(lst);
			if (!IsA(node, Expr))
				continue;
			rlst = TidqualFromExpr(varno, (Expr *) node);
			if (rlst)
				break;
		}
	}
	else if (or_clause(node))
	{
		foreach(lst, expr->args)
		{
			node = lfirst(lst);
			if (IsA(node, Expr) &&
				(frtn = TidqualFromExpr(varno, (Expr *) node)))
				rlst = nconc(rlst, frtn);
			else
			{
				if (rlst)
					freeList(rlst);
				rlst = NIL;
				break;
			}
		}
	}
	return rlst;
}

static List *
TidqualFromRestrictinfo(List *relids, List *restrictinfo)
{
	List	   *lst,
			   *rlst = NIL;
	int			varno;
	Node	   *node;
	Expr	   *expr;

	if (length(relids) != 1)
		return NIL;
	varno = lfirsti(relids);
	foreach(lst, restrictinfo)
	{
		node = lfirst(lst);
		if (!IsA(node, RestrictInfo))
			continue;
		expr = ((RestrictInfo *) node)->clause;
		rlst = TidqualFromExpr(varno, expr);
		if (rlst)
			break;
	}
	return rlst;
}

/*
 * create_tidscan_joinpaths
 *	  Create innerjoin paths if there are suitable joinclauses.
 *
 * XXX does this actually work?
 */
static void
create_tidscan_joinpaths(Query *root, RelOptInfo *rel)
{
	List	   *rlst = NIL,
			   *lst;

	foreach(lst, rel->joininfo)
	{
		JoinInfo   *joininfo = (JoinInfo *) lfirst(lst);
		List	   *restinfo,
				   *tideval;

		restinfo = joininfo->jinfo_restrictinfo;
		tideval = TidqualFromRestrictinfo(rel->relids, restinfo);
		if (length(tideval) == 1)
		{
			TidPath    *pathnode = makeNode(TidPath);

			pathnode->path.pathtype = T_TidScan;
			pathnode->path.parent = rel;
			pathnode->path.pathkeys = NIL;
			pathnode->tideval = tideval;
			pathnode->unjoined_relids = joininfo->unjoined_relids;

			cost_tidscan(&pathnode->path, root, rel, tideval);

			rlst = lappend(rlst, pathnode);
		}
	}
	rel->innerjoin = nconc(rel->innerjoin, rlst);
}

/*
 * create_tidscan_paths
 *	  Creates paths corresponding to tid direct scans of the given rel.
 *	  Candidate paths are added to the rel's pathlist (using add_path).
 */
void
create_tidscan_paths(Query *root, RelOptInfo *rel)
{
	List	   *tideval = TidqualFromRestrictinfo(rel->relids,
												  rel->baserestrictinfo);

	if (tideval)
		add_path(rel, (Path *) create_tidscan_path(root, rel, tideval));
	create_tidscan_joinpaths(root, rel);
}