createplan.c

PostgreSQL7.4.6 for Linux

 *		in at runtime.
 *
 * Ideally the order should be driven by a combination of execution cost and
 * selectivity, but unfortunately we have so little information about
 * execution cost of operators that it's really hard to do anything smart.
 * For now, we just move any quals that contain SubPlan references (but not
 * InitPlan references) to the end of the list.
 */
static List *
order_qual_clauses(Query *root, List *clauses)
{
	FastList	nosubplans;
	FastList	withsubplans;
	List	   *l;

	/* No need to work hard if the query is subselect-free */
	if (!root->hasSubLinks)
		return clauses;

	FastListInit(&nosubplans);
	FastListInit(&withsubplans);
	foreach(l, clauses)
	{
		Node	   *clause = lfirst(l);

		if (contain_subplans(clause))
			FastAppend(&withsubplans, clause);
		else
			FastAppend(&nosubplans, clause);
	}

	FastConcFast(&nosubplans, &withsubplans);
	return FastListValue(&nosubplans);
}

/*
 * Copy cost and size info from a Path node to the Plan node created from it.
 * The executor won't use this info, but it's needed by EXPLAIN.
 */
static void
copy_path_costsize(Plan *dest, Path *src)
{
	if (src)
	{
		dest->startup_cost = src->startup_cost;
		dest->total_cost = src->total_cost;
		dest->plan_rows = src->parent->rows;
		dest->plan_width = src->parent->width;
	}
	else
	{
		dest->startup_cost = 0;
		dest->total_cost = 0;
		dest->plan_rows = 0;
		dest->plan_width = 0;
	}
}

/*
 * Copy cost and size info from a lower plan node to an inserted node.
 * This is not critical, since the decisions have already been made,
 * but it helps produce more reasonable-looking EXPLAIN output.
 * (Some callers alter the info after copying it.)
 */
static void
copy_plan_costsize(Plan *dest, Plan *src)
{
	if (src)
	{
		dest->startup_cost = src->startup_cost;
		dest->total_cost = src->total_cost;
		dest->plan_rows = src->plan_rows;
		dest->plan_width = src->plan_width;
	}
	else
	{
		dest->startup_cost = 0;
		dest->total_cost = 0;
		dest->plan_rows = 0;
		dest->plan_width = 0;
	}
}


/*****************************************************************************
 *
 *	PLAN NODE BUILDING ROUTINES
 *
 * Some of these are exported because they are called to build plan nodes
 * in contexts where we're not deriving the plan node from a path node.
 *
 *****************************************************************************/

static SeqScan *
make_seqscan(List *qptlist,
			 List *qpqual,
			 Index scanrelid)
{
	SeqScan    *node = makeNode(SeqScan);
	Plan	   *plan = &node->plan;

	/* cost should be inserted by caller */
	plan->targetlist = qptlist;
	plan->qual = qpqual;
	plan->lefttree = NULL;
	plan->righttree = NULL;
	node->scanrelid = scanrelid;

	return node;
}

static IndexScan *
make_indexscan(List *qptlist,
			   List *qpqual,
			   Index scanrelid,
			   List *indxid,
			   List *indxqual,
			   List *indxqualorig,
			   ScanDirection indexscandir)
{
	IndexScan  *node = makeNode(IndexScan);
	Plan	   *plan = &node->scan.plan;

	/* cost should be inserted by caller */
	plan->targetlist = qptlist;
	plan->qual = qpqual;
	plan->lefttree = NULL;
	plan->righttree = NULL;
	node->scan.scanrelid = scanrelid;
	node->indxid = indxid;
	node->indxqual = indxqual;
	node->indxqualorig = indxqualorig;
	node->indxorderdir = indexscandir;

	return node;
}

static TidScan *
make_tidscan(List *qptlist,
			 List *qpqual,
			 Index scanrelid,
			 List *tideval)
{
	TidScan    *node = makeNode(TidScan);
	Plan	   *plan = &node->scan.plan;

	/* cost should be inserted by caller */
	plan->targetlist = qptlist;
	plan->qual = qpqual;
	plan->lefttree = NULL;
	plan->righttree = NULL;
	node->scan.scanrelid = scanrelid;
	node->tideval = tideval;

	return node;
}

SubqueryScan *
make_subqueryscan(List *qptlist,
				  List *qpqual,
				  Index scanrelid,
				  Plan *subplan)
{
	SubqueryScan *node = makeNode(SubqueryScan);
	Plan	   *plan = &node->scan.plan;

	/*
	 * Cost is figured here for the convenience of prepunion.c.  Note this
	 * is only correct for the case where qpqual is empty; otherwise
	 * caller should overwrite cost with a better estimate.
	 */
	copy_plan_costsize(plan, subplan);
	plan->total_cost += cpu_tuple_cost * subplan->plan_rows;

	plan->targetlist = qptlist;
	plan->qual = qpqual;
	plan->lefttree = NULL;
	plan->righttree = NULL;
	node->scan.scanrelid = scanrelid;
	node->subplan = subplan;

	return node;
}

static FunctionScan *
make_functionscan(List *qptlist,
				  List *qpqual,
				  Index scanrelid)
{
	FunctionScan *node = makeNode(FunctionScan);
	Plan	   *plan = &node->scan.plan;

	/* cost should be inserted by caller */
	plan->targetlist = qptlist;
	plan->qual = qpqual;
	plan->lefttree = NULL;
	plan->righttree = NULL;
	node->scan.scanrelid = scanrelid;

	return node;
}

Append *
make_append(List *appendplans, bool isTarget, List *tlist)
{
	Append	   *node = makeNode(Append);
	Plan	   *plan = &node->plan;
	List	   *subnode;

	/*
	 * Compute cost as sum of subplan costs.  We charge nothing extra for
	 * the Append itself, which perhaps is too optimistic, but since it
	 * doesn't do any selection or projection, it is a pretty cheap node.
	 */
	plan->startup_cost = 0;
	plan->total_cost = 0;
	plan->plan_rows = 0;
	plan->plan_width = 0;
	foreach(subnode, appendplans)
	{
		Plan	   *subplan = (Plan *) lfirst(subnode);

		if (subnode == appendplans)		/* first node? */
			plan->startup_cost = subplan->startup_cost;
		plan->total_cost += subplan->total_cost;
		plan->plan_rows += subplan->plan_rows;
		if (plan->plan_width < subplan->plan_width)
			plan->plan_width = subplan->plan_width;
	}

	plan->targetlist = tlist;
	plan->qual = NIL;
	plan->lefttree = NULL;
	plan->righttree = NULL;
	node->appendplans = appendplans;
	node->isTarget = isTarget;

	return node;
}

static NestLoop *
make_nestloop(List *tlist,
			  List *joinclauses,
			  List *otherclauses,
			  Plan *lefttree,
			  Plan *righttree,
			  JoinType jointype)
{
	NestLoop   *node = makeNode(NestLoop);
	Plan	   *plan = &node->join.plan;

	/* cost should be inserted by caller */
	plan->targetlist = tlist;
	plan->qual = otherclauses;
	plan->lefttree = lefttree;
	plan->righttree = righttree;
	node->join.jointype = jointype;
	node->join.joinqual = joinclauses;

	return node;
}

static HashJoin *
make_hashjoin(List *tlist,
			  List *joinclauses,
			  List *otherclauses,
			  List *hashclauses,
			  Plan *lefttree,
			  Plan *righttree,
			  JoinType jointype)
{
	HashJoin   *node = makeNode(HashJoin);
	Plan	   *plan = &node->join.plan;

	/* cost should be inserted by caller */
	plan->targetlist = tlist;
	plan->qual = otherclauses;
	plan->lefttree = lefttree;
	plan->righttree = righttree;
	node->hashclauses = hashclauses;
	node->join.jointype = jointype;
	node->join.joinqual = joinclauses;

	return node;
}

static Hash *
make_hash(List *tlist, List *hashkeys, Plan *lefttree)
{
	Hash	   *node = makeNode(Hash);
	Plan	   *plan = &node->plan;

	copy_plan_costsize(plan, lefttree);

	/*
	 * For plausibility, make startup & total costs equal total cost of
	 * input plan; this only affects EXPLAIN display not decisions.
	 */
	plan->startup_cost = plan->total_cost;
	plan->targetlist = tlist;
	plan->qual = NIL;
	plan->lefttree = lefttree;
	plan->righttree = NULL;
	node->hashkeys = hashkeys;

	return node;
}

static MergeJoin *
make_mergejoin(List *tlist,
			   List *joinclauses,
			   List *otherclauses,
			   List *mergeclauses,
			   Plan *lefttree,
			   Plan *righttree,
			   JoinType jointype)
{
	MergeJoin  *node = makeNode(MergeJoin);
	Plan	   *plan = &node->join.plan;

	/* cost should be inserted by caller */
	plan->targetlist = tlist;
	plan->qual = otherclauses;
	plan->lefttree = lefttree;
	plan->righttree = righttree;
	node->mergeclauses = mergeclauses;
	node->join.jointype = jointype;
	node->join.joinqual = joinclauses;

	return node;
}

/*
 * make_sort --- basic routine to build a Sort plan node
 *
 * Caller must have built the sortColIdx and sortOperators arrays already.
 */
static Sort *
make_sort(Query *root, List *tlist, Plan *lefttree, int numCols,
		  AttrNumber *sortColIdx, Oid *sortOperators)
{
	Sort	   *node = makeNode(Sort);
	Plan	   *plan = &node->plan;
	Path		sort_path;		/* dummy for result of cost_sort */

	copy_plan_costsize(plan, lefttree); /* only care about copying size */
	cost_sort(&sort_path, root, NIL,
			  lefttree->total_cost,
			  lefttree->plan_rows,
			  lefttree->plan_width);
	plan->startup_cost = sort_path.startup_cost;
	plan->total_cost = sort_path.total_cost;
	plan->targetlist = tlist;
	plan->qual = NIL;
	plan->lefttree = lefttree;
	plan->righttree = NULL;
	node->numCols = numCols;
	node->sortColIdx = sortColIdx;
	node->sortOperators = sortOperators;

	return node;
}

/*
 * add_sort_column --- utility subroutine for building sort info arrays
 *
 * We need this routine because the same column might be selected more than
 * once as a sort key column; if so, the extra mentions are redundant.
 *
 * Caller is assumed to have allocated the arrays large enough for the
 * max possible number of columns.	Return value is the new column count.
 */
static int
add_sort_column(AttrNumber colIdx, Oid sortOp,
				int numCols, AttrNumber *sortColIdx, Oid *sortOperators)
{
	int			i;

	for (i = 0; i < numCols; i++)
	{
		if (sortColIdx[i] == colIdx)
		{
			/* Already sorting by this col, so extra sort key is useless */
			return numCols;
		}
	}

	/* Add the column */
	sortColIdx[numCols] = colIdx;
	sortOperators[numCols] = sortOp;
	return numCols + 1;
}

/*
 * make_sort_from_pathkeys
 *	  Create sort plan to sort according to given pathkeys
 *
 *	  'lefttree' is the node which yields input tuples
 *	  'pathkeys' is the list of pathkeys by which the result is to be sorted
 *
 * We must convert the pathkey information into arrays of sort key column
 * numbers and sort operator OIDs.
 *
 * If the pathkeys include expressions that aren't simple Vars, we will
 * usually need to add resjunk items to the input plan's targetlist to
 * compute these expressions (since the Sort node itself won't do it).
 * If the input plan type isn't one that can do projections, this means
 * adding a Result node just to do the projection.
 */
static Sort *
make_sort_from_pathkeys(Query *root, Plan *lefttree, List *pathkeys)
{
	List	   *tlist = lefttree->targetlist;
	List	   *sort_tlist;
	List	   *i;
	int			numsortkeys;
	AttrNumber *sortColIdx;
	Oid		   *sortOperators;

	/* We will need at most length(pathkeys) sort columns; possibly less */
	numsortkeys = length(pathkeys);
	sortColIdx = (AttrNumber *) palloc(numsortkeys * sizeof(AttrNumber));
	sortOperators = (Oid *) palloc(numsortkeys * sizeof(Oid));

	numsortkeys = 0;

	foreach(i, pathkeys)
	{
		List	   *keysublist = (List *) lfirst(i);
		PathKeyItem *pathkey = NULL;
		Resdom	   *resdom = NULL;
		List	   *j;

		/*
		 * We can sort by any one of the sort key items listed in this
		 * sublist.  For now, we take the first one that corresponds to an
		 * available Var in the tlist.	If there isn't any, use the first
		 * one that is an expression in the input's vars.
		 *
		 * XXX if we have a choice, is there any way of figuring out which
		 * might be cheapest to execute?  (For example, int4lt is likely
		 * much cheaper to execute than numericlt, but both might appear
		 * in the same pathkey sublist...)	Not clear that we ever will
		 * have a choice in practice, so it may not matter.
		 */
		foreach(j, keysublist)
		{
			pathkey = lfirst(j);
			Assert(IsA(pathkey, PathKeyItem));
			resdom = tlist_member(pathkey->key, tlist);
			if (resdom)
				break;
		}
		if (!resdom)
		{
			/* No matching Var; look for a computable expression */
			foreach(j, keysublist)
			{
				List   *exprvars;
				List   *k;

				pathkey = lfirst(j);
				exprvars = pull_var_clause(pathkey->key, false);
				foreach(k, exprvars)
				{