createplan.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

	 * parent-rel Vars it'll be asked to emit.
	 */
	if (best_path->subpaths == NIL)
	{
		/* Generate a Result plan with constant-FALSE gating qual */
		return (Plan *) make_result(tlist,
									(Node *) list_make1(makeBoolConst(false,
																	  false)),
									NULL);
	}

	/* Normal case with multiple subpaths */
	foreach(subpaths, best_path->subpaths)
	{
		Path	   *subpath = (Path *) lfirst(subpaths);

		subplans = lappend(subplans, create_plan(root, subpath));
	}

	plan = make_append(subplans, false, tlist);

	return (Plan *) plan;
}

/*
 * create_result_plan
 *	  Create a Result plan for 'best_path' and (recursively) plans
 *	  for its subpaths.
 *
 *	  Returns a Plan node.
 */
static Result *
create_result_plan(PlannerInfo *root, ResultPath *best_path)
{
	Result	   *plan;
	List	   *tlist;
	List	   *constclauses;
	Plan	   *subplan;

	if (best_path->path.parent)
		tlist = build_relation_tlist(best_path->path.parent);
	else
		tlist = NIL;			/* will be filled in later */

	if (best_path->subpath)
		subplan = create_plan(root, best_path->subpath);
	else
		subplan = NULL;

	constclauses = order_qual_clauses(root, best_path->constantqual);

	plan = make_result(tlist, (Node *) constclauses, subplan);

	return plan;
}

/*
 * create_material_plan
 *	  Create a Material plan for 'best_path' and (recursively) plans
 *	  for its subpaths.
 *
 *	  Returns a Plan node.
 */
static Material *
create_material_plan(PlannerInfo *root, MaterialPath *best_path)
{
	Material   *plan;
	Plan	   *subplan;

	subplan = create_plan(root, best_path->subpath);

	/* We don't want any excess columns in the materialized tuples */
	disuse_physical_tlist(subplan, best_path->subpath);

	plan = make_material(subplan);

	copy_path_costsize(&plan->plan, (Path *) best_path);

	return plan;
}

/*
 * create_unique_plan
 *	  Create a Unique plan for 'best_path' and (recursively) plans
 *	  for its subpaths.
 *
 *	  Returns a Plan node.
 */
static Plan *
create_unique_plan(PlannerInfo *root, UniquePath *best_path)
{
	Plan	   *plan;
	Plan	   *subplan;
	List	   *uniq_exprs;
	List	   *newtlist;
	int			nextresno;
	bool		newitems;
	int			numGroupCols;
	AttrNumber *groupColIdx;
	int			groupColPos;
	ListCell   *l;

	subplan = create_plan(root, best_path->subpath);

	/* Done if we don't need to do any actual unique-ifying */
	if (best_path->umethod == UNIQUE_PATH_NOOP)
		return subplan;

	/*----------
	 * As constructed, the subplan has a "flat" tlist containing just the
	 * Vars needed here and at upper levels.  The values we are supposed
	 * to unique-ify may be expressions in these variables.  We have to
	 * add any such expressions to the subplan's tlist.
	 *
	 * The subplan may have a "physical" tlist if it is a simple scan plan.
	 * This should be left as-is if we don't need to add any expressions;
	 * but if we do have to add expressions, then a projection step will be
	 * needed at runtime anyway, and so we may as well remove unneeded items.
	 * Therefore newtlist starts from build_relation_tlist() not just a
	 * copy of the subplan's tlist; and we don't install it into the subplan
	 * unless stuff has to be added.
	 *
	 * To find the correct list of values to unique-ify, we look in the
	 * information saved for IN expressions.  If this code is ever used in
	 * other scenarios, some other way of finding what to unique-ify will
	 * be needed.
	 *----------
	 */
	uniq_exprs = NIL;			/* just to keep compiler quiet */
	foreach(l, root->in_info_list)
	{
		InClauseInfo *ininfo = (InClauseInfo *) lfirst(l);

		if (bms_equal(ininfo->righthand, best_path->path.parent->relids))
		{
			uniq_exprs = ininfo->sub_targetlist;
			break;
		}
	}
	if (l == NULL)				/* fell out of loop? */
		elog(ERROR, "could not find UniquePath in in_info_list");

	/* initialize modified subplan tlist as just the "required" vars */
	newtlist = build_relation_tlist(best_path->path.parent);
	nextresno = list_length(newtlist) + 1;
	newitems = false;

	foreach(l, uniq_exprs)
	{
		Node	   *uniqexpr = lfirst(l);
		TargetEntry *tle;

		tle = tlist_member(uniqexpr, newtlist);
		if (!tle)
		{
			tle = makeTargetEntry((Expr *) uniqexpr,
								  nextresno,
								  NULL,
								  false);
			newtlist = lappend(newtlist, tle);
			nextresno++;
			newitems = true;
		}
	}

	if (newitems)
	{
		/*
		 * If the top plan node can't do projections, we need to add a Result
		 * node to help it along.
		 */
		if (!is_projection_capable_plan(subplan))
			subplan = (Plan *) make_result(newtlist, NULL, subplan);
		else
			subplan->targetlist = newtlist;
	}

	/*
	 * Build control information showing which subplan output columns are to
	 * be examined by the grouping step.  Unfortunately we can't merge this
	 * with the previous loop, since we didn't then know which version of the
	 * subplan tlist we'd end up using.
	 */
	newtlist = subplan->targetlist;
	numGroupCols = list_length(uniq_exprs);
	groupColIdx = (AttrNumber *) palloc(numGroupCols * sizeof(AttrNumber));
	groupColPos = 0;

	foreach(l, uniq_exprs)
	{
		Node	   *uniqexpr = lfirst(l);
		TargetEntry *tle;

		tle = tlist_member(uniqexpr, newtlist);
		if (!tle)				/* shouldn't happen */
			elog(ERROR, "failed to find unique expression in subplan tlist");
		groupColIdx[groupColPos++] = tle->resno;
	}

	if (best_path->umethod == UNIQUE_PATH_HASH)
	{
		long		numGroups;

		numGroups = (long) Min(best_path->rows, (double) LONG_MAX);

		/*
		 * Since the Agg node is going to project anyway, we can give it the
		 * minimum output tlist, without any stuff we might have added to the
		 * subplan tlist.
		 */
		plan = (Plan *) make_agg(root,
								 build_relation_tlist(best_path->path.parent),
								 NIL,
								 AGG_HASHED,
								 numGroupCols,
								 groupColIdx,
								 numGroups,
								 0,
								 subplan);
	}
	else
	{
		List	   *sortList = NIL;

		for (groupColPos = 0; groupColPos < numGroupCols; groupColPos++)
		{
			TargetEntry *tle;

			tle = get_tle_by_resno(subplan->targetlist,
								   groupColIdx[groupColPos]);
			Assert(tle != NULL);
			sortList = addTargetToSortList(NULL, tle,
										   sortList, subplan->targetlist,
										   SORTBY_ASC, NIL, false);
		}
		plan = (Plan *) make_sort_from_sortclauses(root, sortList, subplan);
		plan = (Plan *) make_unique(plan, sortList);
	}

	/* Adjust output size estimate (other fields should be OK already) */
	plan->plan_rows = best_path->rows;

	return plan;
}


/*****************************************************************************
 *
 *	BASE-RELATION SCAN METHODS
 *
 *****************************************************************************/


/*
 * create_seqscan_plan
 *	 Returns a seqscan plan for the base relation scanned by 'best_path'
 *	 with restriction clauses 'scan_clauses' and targetlist 'tlist'.
 */
static SeqScan *
create_seqscan_plan(PlannerInfo *root, Path *best_path,
					List *tlist, List *scan_clauses)
{
	SeqScan    *scan_plan;
	Index		scan_relid = best_path->parent->relid;

	/* it should be a base rel... */
	Assert(scan_relid > 0);
	Assert(best_path->parent->rtekind == RTE_RELATION);

	/* Reduce RestrictInfo list to bare expressions */
	scan_clauses = get_actual_clauses(scan_clauses);

	/* Sort clauses into best execution order */
	scan_clauses = order_qual_clauses(root, scan_clauses);

	scan_plan = make_seqscan(tlist,
							 scan_clauses,
							 scan_relid);

	copy_path_costsize(&scan_plan->plan, best_path);

	return scan_plan;
}

/*
 * create_indexscan_plan
 *	  Returns an indexscan plan for the base relation scanned by 'best_path'
 *	  with restriction clauses 'scan_clauses' and targetlist 'tlist'.
 *
 * The indexquals list of the path contains implicitly-ANDed qual conditions.
 * The list can be empty --- then no index restrictions will be applied during
 * the scan.
 *
 * If nonlossy_clauses isn't NULL, *nonlossy_clauses receives a list of the
 * nonlossy indexquals.
 */
static IndexScan *
create_indexscan_plan(PlannerInfo *root,
					  IndexPath *best_path,
					  List *tlist,
					  List *scan_clauses,
					  List **nonlossy_clauses)
{
	List	   *indexquals = best_path->indexquals;
	Index		baserelid = best_path->path.parent->relid;
	Oid			indexoid = best_path->indexinfo->indexoid;
	List	   *qpqual;
	List	   *stripped_indexquals;
	List	   *fixed_indexquals;
	List	   *nonlossy_indexquals;
	List	   *indexstrategy;
	List	   *indexsubtype;
	ListCell   *l;
	IndexScan  *scan_plan;

	/* it should be a base rel... */
	Assert(baserelid > 0);
	Assert(best_path->path.parent->rtekind == RTE_RELATION);

	/*
	 * Build "stripped" indexquals structure (no RestrictInfos) to pass to
	 * executor as indexqualorig
	 */
	stripped_indexquals = get_actual_clauses(indexquals);

	/*
	 * The executor needs a copy with the indexkey on the left of each clause
	 * and with index attr numbers substituted for table ones. This pass also
	 * gets strategy info and looks for "lossy" operators.
	 */
	fix_indexqual_references(indexquals, best_path,
							 &fixed_indexquals,
							 &nonlossy_indexquals,
							 &indexstrategy,
							 &indexsubtype);

	/* pass back nonlossy quals if caller wants 'em */
	if (nonlossy_clauses)
		*nonlossy_clauses = nonlossy_indexquals;

	/*
	 * If this is an innerjoin scan, the indexclauses will contain join
	 * clauses that are not present in scan_clauses (since the passed-in value
	 * is just the rel's baserestrictinfo list).  We must add these clauses to
	 * scan_clauses to ensure they get checked.  In most cases we will remove
	 * the join clauses again below, but if a join clause contains a special
	 * operator, we need to make sure it gets into the scan_clauses.
	 *
	 * Note: pointer comparison should be enough to determine RestrictInfo
	 * matches.
	 */
	if (best_path->isjoininner)
		scan_clauses = list_union_ptr(scan_clauses, best_path->indexclauses);

	/*
	 * The qpqual list must contain all restrictions not automatically handled
	 * by the index.  All the predicates in the indexquals will be checked
	 * (either by the index itself, or by nodeIndexscan.c), but if there are
	 * any "special" operators involved then they must be included in qpqual.
	 * Also, any lossy index operators must be rechecked in the qpqual.  The
	 * upshot is that qpqual must contain scan_clauses minus whatever appears
	 * in nonlossy_indexquals.
	 *
	 * In normal cases simple pointer equality checks will be enough to spot
	 * duplicate RestrictInfos, so we try that first.  In some situations
	 * (particularly with OR'd index conditions) we may have scan_clauses that
	 * are not equal to, but are logically implied by, the index quals; so we
	 * also try a predicate_implied_by() check to see if we can discard quals
	 * that way.  (predicate_implied_by assumes its first input contains only
	 * immutable functions, so we have to check that.)
	 *
	 * We can also discard quals that are implied by a partial index's
	 * predicate, but only in a plain SELECT; when scanning a target relation
	 * of UPDATE/DELETE/SELECT FOR UPDATE, we must leave such quals in the
	 * plan so that they'll be properly rechecked by EvalPlanQual testing.
	 *
	 * While at it, we strip off the RestrictInfos to produce a list of plain
	 * expressions.
	 */
	qpqual = NIL;
	foreach(l, scan_clauses)
	{
		RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);

		Assert(IsA(rinfo, RestrictInfo));
		if (list_member_ptr(nonlossy_indexquals, rinfo))
			continue;
		if (!contain_mutable_functions((Node *) rinfo->clause))
		{
			List	   *clausel = list_make1(rinfo->clause);

			if (predicate_implied_by(clausel, nonlossy_indexquals))
				continue;
			if (best_path->indexinfo->indpred)
			{
				if (baserelid != root->parse->resultRelation &&
					!list_member_int(root->parse->rowMarks, baserelid))
					if (predicate_implied_by(clausel,
											 best_path->indexinfo->indpred))
						continue;
			}
		}
		qpqual = lappend(qpqual, rinfo->clause);
	}

	/* Sort clauses into best execution order */
	qpqual = order_qual_clauses(root, qpqual);

	/* Finally ready to build the plan node */
	scan_plan = make_indexscan(tlist,
							   qpqual,
							   baserelid,
							   indexoid,
							   fixed_indexquals,
							   stripped_indexquals,
							   indexstrategy,
							   indexsubtype,
							   best_path->indexscandir);

	copy_path_costsize(&scan_plan->scan.plan, &best_path->path);
	/* use the indexscan-specific rows estimate, not the parent rel's */
	scan_plan->scan.plan.plan_rows = best_path->rows;

	return scan_plan;
}

/*
 * create_bitmap_scan_plan
 *	  Returns a bitmap scan plan for the base relation scanned by 'best_path'
 *	  with restriction clauses 'scan_clauses' and targetlist 'tlist'.
 */
static BitmapHeapScan *
create_bitmap_scan_plan(PlannerInfo *root,
						BitmapHeapPath *best_path,
						List *tlist,
						List *scan_clauses)
{
	Index		baserelid = best_path->path.parent->relid;
	Plan	   *bitmapqualplan;
	List	   *bitmapqualorig;
	List	   *indexquals;
	List	   *qpqual;
	ListCell   *l;
	BitmapHeapScan *scan_plan;

	/* it should be a base rel... */
	Assert(baserelid > 0);
	Assert(best_path->path.parent->rtekind == RTE_RELATION);