createplan.c

PostgreSQL7.4.6 for Linux

	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(Query *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->targetlist, 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(Query *root, UniquePath *best_path)
{
	Plan	   *plan;
	Plan	   *subplan;
	List	   *uniq_exprs;
	int			numGroupCols;
	AttrNumber *groupColIdx;
	int			groupColPos;
	List	   *newtlist;
	int			nextresno;
	bool		newitems;
	List	   *my_tlist;
	List	   *l;

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

	/*
	 * 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.  We then build
	 * control information showing which subplan output columns are to be
	 * examined by the grouping step.  (Since we do not remove any
	 * existing subplan outputs, not all the output columns may be used
	 * for grouping.)
	 *
	 * Note: the reason we don't remove any subplan outputs is that there are
	 * scenarios where a Var is needed at higher levels even though it is
	 * not one of the nominal outputs of an IN clause.	Consider WHERE x
	 * IN (SELECT y FROM t1,t2 WHERE y = z) Implied equality deduction
	 * will generate an "x = z" clause, which may get used instead of "x =
	 * y" in the upper join step.  Therefore the sub-select had better
	 * deliver both y and z in its targetlist.	It is sufficient to
	 * unique-ify on y, however.
	 *
	 * 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 == NIL)				/* fell out of loop? */
		elog(ERROR, "could not find UniquePath in in_info_list");

	/* set up to record positions of unique columns */
	numGroupCols = length(uniq_exprs);
	groupColIdx = (AttrNumber *) palloc(numGroupCols * sizeof(AttrNumber));
	groupColPos = 0;
	/* not sure if tlist might be shared with other nodes, so copy */
	newtlist = copyObject(subplan->targetlist);
	nextresno = length(newtlist) + 1;
	newitems = false;

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

		tle = tlistentry_member(uniqexpr, newtlist);
		if (!tle)
		{
			tle = makeTargetEntry(makeResdom(nextresno,
											 exprType(uniqexpr),
											 exprTypmod(uniqexpr),
											 NULL,
											 false),
								  (Expr *) uniqexpr);
			newtlist = lappend(newtlist, tle);
			nextresno++;
			newitems = true;
		}
		groupColIdx[groupColPos++] = tle->resdom->resno;
	}

	if (newitems)
	{
		/*
		 * If the top plan node can't do projections, we need to add a
		 * Result node to help it along.
		 *
		 * Currently, the only non-projection-capable plan type we can see
		 * here is Append.
		 */
		if (IsA(subplan, Append))
			subplan = (Plan *) make_result(newtlist, NULL, subplan);
		else
			subplan->targetlist = newtlist;
	}

	/* Copy tlist again to make one we can put sorting labels on */
	my_tlist = copyObject(subplan->targetlist);

	if (best_path->use_hash)
	{
		long		numGroups;

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

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

	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(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);

	scan_plan = make_seqscan(tlist,
							 scan_clauses,
							 scan_relid);

	copy_path_costsize(&scan_plan->plan, best_path);

	return scan_plan;
}

/*
 * create_indexscan_plan
 *	  Returns a indexscan plan for the base relation scanned by 'best_path'
 *	  with restriction clauses 'scan_clauses' and targetlist 'tlist'.
 *
 * The indexqual of the path contains a sublist of implicitly-ANDed qual
 * conditions for each scan of the index(es); if there is more than one
 * scan then the retrieved tuple sets are ORed together.  The indexqual
 * and indexinfo lists must have the same length, ie, the number of scans
 * that will occur.  Note it is possible for a qual condition sublist
 * to be empty --- then no index restrictions will be applied during that
 * scan.
 */
static IndexScan *
create_indexscan_plan(Query *root,
					  IndexPath *best_path,
					  List *tlist,
					  List *scan_clauses)
{
	List	   *indxqual = best_path->indexqual;
	Index		baserelid = best_path->path.parent->relid;
	List	   *qpqual;
	Expr	   *indxqual_or_expr = NULL;
	List	   *fixed_indxqual;
	List	   *recheck_indxqual;
	FastList	indexids;
	List	   *ixinfo;
	IndexScan  *scan_plan;

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

	/*
	 * Build list of index OIDs.
	 */
	FastListInit(&indexids);
	foreach(ixinfo, best_path->indexinfo)
	{
		IndexOptInfo *index = (IndexOptInfo *) lfirst(ixinfo);

		FastAppendo(&indexids, index->indexoid);
	}

	/*
	 * The qpqual list must contain all restrictions not automatically
	 * handled by the index.  Normally the predicates in the indxqual are
	 * checked fully by the index, but if the index is "lossy" for a
	 * particular operator (as signaled by the amopreqcheck flag in
	 * pg_amop), then we need to double-check that predicate in qpqual,
	 * because the index may return more tuples than match the predicate.
	 *
	 * Since the indexquals were generated from the restriction clauses given
	 * by scan_clauses, there will normally be some duplications between
	 * the lists.  We get rid of the duplicates, then add back if lossy.
	 */
	if (length(indxqual) > 1)
	{
		/*
		 * Build an expression representation of the indexqual, expanding
		 * the implicit OR and AND semantics of the first- and
		 * second-level lists.
		 */
		FastList	orclauses;
		List	   *orclause;

		FastListInit(&orclauses);
		foreach(orclause, indxqual)
			FastAppend(&orclauses, make_ands_explicit(lfirst(orclause)));
		indxqual_or_expr = make_orclause(FastListValue(&orclauses));

		qpqual = set_difference(scan_clauses, makeList1(indxqual_or_expr));
	}
	else if (indxqual != NIL)
	{
		/*
		 * Here, we can simply treat the first sublist as an independent
		 * set of qual expressions, since there is no top-level OR
		 * behavior.
		 */
		qpqual = set_difference(scan_clauses, lfirst(indxqual));
	}
	else
		qpqual = scan_clauses;

	/*
	 * 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 looks for "lossy" operators.
	 */
	fix_indxqual_references(indxqual, best_path,
							&fixed_indxqual, &recheck_indxqual);

	/*
	 * If there were any "lossy" operators, need to add back the
	 * appropriate qual clauses to the qpqual.	When there is just one
	 * indexscan being performed (ie, we have simple AND semantics), we
	 * can just add the lossy clauses themselves to qpqual.  If we have
	 * OR-of-ANDs, we'd better add the entire original indexqual to make
	 * sure that the semantics are correct.
	 */
	if (recheck_indxqual != NIL)
	{
		if (indxqual_or_expr)
		{
			/* Better do a deep copy of the original scanclauses */
			qpqual = lappend(qpqual, copyObject(indxqual_or_expr));
		}
		else
		{
			/* Subroutine already copied quals, so just append to list */
			Assert(length(recheck_indxqual) == 1);
			qpqual = nconc(qpqual, (List *) lfirst(recheck_indxqual));
		}
	}

	/* Finally ready to build the plan node */
	scan_plan = make_indexscan(tlist,
							   qpqual,
							   baserelid,
							   FastListValue(&indexids),
							   fixed_indxqual,
							   indxqual,
							   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_tidscan_plan
 *	 Returns a tidscan plan for the base relation scanned by 'best_path'
 *	 with restriction clauses 'scan_clauses' and targetlist 'tlist'.
 */
static TidScan *
create_tidscan_plan(TidPath *best_path, List *tlist, List *scan_clauses)
{
	TidScan    *scan_plan;
	Index		scan_relid = best_path->path.parent->relid;

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

	scan_plan = make_tidscan(tlist,
							 scan_clauses,
							 scan_relid,
							 best_path->tideval);

	copy_path_costsize(&scan_plan->scan.plan, &best_path->path);

	return scan_plan;
}

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

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

	scan_plan = make_subqueryscan(tlist,
								  scan_clauses,
								  scan_relid,
								  best_path->parent->subplan);

	copy_path_costsize(&scan_plan->scan.plan, best_path);

	return scan_plan;
}

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

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

	scan_plan = make_functionscan(tlist, scan_clauses, scan_relid);

	copy_path_costsize(&scan_plan->scan.plan, best_path);

	return scan_plan;
}

/*****************************************************************************
 *
 *	JOIN METHODS
 *
 *****************************************************************************/

static NestLoop *
create_nestloop_plan(Query *root,
					 NestPath *best_path,
					 Plan *outer_plan,
					 Plan *inner_plan)
{
	List	   *tlist = build_relation_tlist(best_path->path.parent);
	List	   *joinrestrictclauses = best_path->joinrestrictinfo;
	List	   *joinclauses;
	List	   *otherclauses;
	NestLoop   *join_plan;

	if (IsA(best_path->innerjoinpath, IndexPath))
	{
		/*
		 * 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 may remove those join clauses from the list
		 * of clauses that have to be checked as qpquals at the join node
		 * --- but only if there's just one indexscan in the inner path
		 * (otherwise, several different sets of clauses are being ORed
		 * together).
		 *
		 * We can also remove any join clauses that are redundant with those
		 * being used in the index scan; prior redundancy checks will not
		 * have caught this case because the join clauses would never have
		 * been put in the same joininfo list.
		 *
		 * This would be a waste of time if the indexpath was an ordinary
		 * indexpath and not a special innerjoin path.	We will skip it in
		 * that case since indexjoinclauses is NIL in an ordinary
		 * indexpath.
		 */
		IndexPath  *innerpath = (IndexPath *) best_path->innerjoinpath;
		List	   *indexjoinclauses = innerpath->indexjoinclauses;

		if (length(indexjoinclauses) == 1)		/* single indexscan? */
		{
			joinrestrictclauses =
				select_nonredundant_join_clauses(root,
												 joinrestrictclauses,
												 lfirst(indexjoinclauses),
												 best_path->jointype);