createplan.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

							  otherclauses,
							  outer_plan,
							  inner_plan,
							  best_path->jointype);

	copy_path_costsize(&join_plan->join.plan, &best_path->path);

	return join_plan;
}

static MergeJoin *
create_mergejoin_plan(PlannerInfo *root,
					  MergePath *best_path,
					  Plan *outer_plan,
					  Plan *inner_plan)
{
	List	   *tlist = build_relation_tlist(best_path->jpath.path.parent);
	List	   *joinclauses;
	List	   *otherclauses;
	List	   *mergeclauses;
	MergeJoin  *join_plan;

	/* Get the join qual clauses (in plain expression form) */
	if (IS_OUTER_JOIN(best_path->jpath.jointype))
	{
		get_actual_join_clauses(best_path->jpath.joinrestrictinfo,
								&joinclauses, &otherclauses);
	}
	else
	{
		/* We can treat all clauses alike for an inner join */
		joinclauses = get_actual_clauses(best_path->jpath.joinrestrictinfo);
		otherclauses = NIL;
	}

	/*
	 * Remove the mergeclauses from the list of join qual clauses, leaving the
	 * list of quals that must be checked as qpquals.
	 */
	mergeclauses = get_actual_clauses(best_path->path_mergeclauses);
	joinclauses = list_difference(joinclauses, mergeclauses);

	/*
	 * Rearrange mergeclauses, if needed, so that the outer variable is always
	 * on the left.
	 */
	mergeclauses = get_switched_clauses(best_path->path_mergeclauses,
							 best_path->jpath.outerjoinpath->parent->relids);

	/* Sort clauses into best execution order */
	/* NB: do NOT reorder the mergeclauses */
	joinclauses = order_qual_clauses(root, joinclauses);
	otherclauses = order_qual_clauses(root, otherclauses);

	/*
	 * Create explicit sort nodes for the outer and inner join paths if
	 * necessary.  The sort cost was already accounted for in the path. Make
	 * sure there are no excess columns in the inputs if sorting.
	 */
	if (best_path->outersortkeys)
	{
		disuse_physical_tlist(outer_plan, best_path->jpath.outerjoinpath);
		outer_plan = (Plan *)
			make_sort_from_pathkeys(root,
									outer_plan,
									best_path->outersortkeys);
	}

	if (best_path->innersortkeys)
	{
		disuse_physical_tlist(inner_plan, best_path->jpath.innerjoinpath);
		inner_plan = (Plan *)
			make_sort_from_pathkeys(root,
									inner_plan,
									best_path->innersortkeys);
	}

	/*
	 * Now we can build the mergejoin node.
	 */
	join_plan = make_mergejoin(tlist,
							   joinclauses,
							   otherclauses,
							   mergeclauses,
							   outer_plan,
							   inner_plan,
							   best_path->jpath.jointype);

	copy_path_costsize(&join_plan->join.plan, &best_path->jpath.path);

	return join_plan;
}

static HashJoin *
create_hashjoin_plan(PlannerInfo *root,
					 HashPath *best_path,
					 Plan *outer_plan,
					 Plan *inner_plan)
{
	List	   *tlist = build_relation_tlist(best_path->jpath.path.parent);
	List	   *joinclauses;
	List	   *otherclauses;
	List	   *hashclauses;
	HashJoin   *join_plan;
	Hash	   *hash_plan;

	/* Get the join qual clauses (in plain expression form) */
	if (IS_OUTER_JOIN(best_path->jpath.jointype))
	{
		get_actual_join_clauses(best_path->jpath.joinrestrictinfo,
								&joinclauses, &otherclauses);
	}
	else
	{
		/* We can treat all clauses alike for an inner join */
		joinclauses = get_actual_clauses(best_path->jpath.joinrestrictinfo);
		otherclauses = NIL;
	}

	/*
	 * Remove the hashclauses from the list of join qual clauses, leaving the
	 * list of quals that must be checked as qpquals.
	 */
	hashclauses = get_actual_clauses(best_path->path_hashclauses);
	joinclauses = list_difference(joinclauses, hashclauses);

	/*
	 * Rearrange hashclauses, if needed, so that the outer variable is always
	 * on the left.
	 */
	hashclauses = get_switched_clauses(best_path->path_hashclauses,
							 best_path->jpath.outerjoinpath->parent->relids);

	/* Sort clauses into best execution order */
	joinclauses = order_qual_clauses(root, joinclauses);
	otherclauses = order_qual_clauses(root, otherclauses);
	hashclauses = order_qual_clauses(root, hashclauses);

	/* We don't want any excess columns in the hashed tuples */
	disuse_physical_tlist(inner_plan, best_path->jpath.innerjoinpath);

	/*
	 * Build the hash node and hash join node.
	 */
	hash_plan = make_hash(inner_plan);
	join_plan = make_hashjoin(tlist,
							  joinclauses,
							  otherclauses,
							  hashclauses,
							  outer_plan,
							  (Plan *) hash_plan,
							  best_path->jpath.jointype);

	copy_path_costsize(&join_plan->join.plan, &best_path->jpath.path);

	return join_plan;
}


/*****************************************************************************
 *
 *	SUPPORTING ROUTINES
 *
 *****************************************************************************/

/*
 * fix_indexqual_references
 *	  Adjust indexqual clauses to the form the executor's indexqual
 *	  machinery needs, and check for recheckable (lossy) index conditions.
 *
 * We have five tasks here:
 *	* Remove RestrictInfo nodes from the input clauses.
 *	* Index keys must be represented by Var nodes with varattno set to the
 *	  index's attribute number, not the attribute number in the original rel.
 *	* If the index key is on the right, commute the clause to put it on the
 *	  left.
 *	* We must construct lists of operator strategy numbers and subtypes
 *	  for the top-level operators of each index clause.
 *	* We must detect any lossy index operators.  The API is that we return
 *	  a list of the input clauses whose operators are NOT lossy.
 *
 * fixed_indexquals receives a modified copy of the indexquals list --- the
 * original is not changed.  Note also that the copy shares no substructure
 * with the original; this is needed in case there is a subplan in it (we need
 * two separate copies of the subplan tree, or things will go awry).
 *
 * nonlossy_indexquals receives a list of the original input clauses (with
 * RestrictInfos) that contain non-lossy operators.
 *
 * indexstrategy receives an integer list of strategy numbers.
 * indexsubtype receives an OID list of strategy subtypes.
 */
static void
fix_indexqual_references(List *indexquals, IndexPath *index_path,
						 List **fixed_indexquals,
						 List **nonlossy_indexquals,
						 List **indexstrategy,
						 List **indexsubtype)
{
	IndexOptInfo *index = index_path->indexinfo;
	ListCell   *l;

	*fixed_indexquals = NIL;
	*nonlossy_indexquals = NIL;
	*indexstrategy = NIL;
	*indexsubtype = NIL;

	/*
	 * For each qual clause, commute if needed to put the indexkey operand on
	 * the left, and then fix its varattno.  (We do not need to change the
	 * other side of the clause.)  Then determine the operator's strategy
	 * number and subtype number, and check for lossy index behavior.
	 */
	foreach(l, indexquals)
	{
		RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
		OpExpr	   *clause;
		OpExpr	   *newclause;
		Oid			opclass;
		int			stratno;
		Oid			stratsubtype;
		bool		recheck;

		Assert(IsA(rinfo, RestrictInfo));
		clause = (OpExpr *) rinfo->clause;
		if (!IsA(clause, OpExpr) ||
			list_length(clause->args) != 2)
			elog(ERROR, "indexqual clause is not binary opclause");

		/*
		 * Make a copy that will become the fixed clause.
		 *
		 * We used to try to do a shallow copy here, but that fails if there
		 * is a subplan in the arguments of the opclause.  So just do a full
		 * copy.
		 */
		newclause = (OpExpr *) copyObject((Node *) clause);

		/*
		 * Check to see if the indexkey is on the right; if so, commute the
		 * clause.	The indexkey should be the side that refers to (only) the
		 * base relation.
		 */
		if (!bms_equal(rinfo->left_relids, index->rel->relids))
			CommuteClause(newclause);

		/*
		 * Now, determine which index attribute this is, change the indexkey
		 * operand as needed, and get the index opclass.
		 */
		linitial(newclause->args) =
			fix_indexqual_operand(linitial(newclause->args),
								  index,
								  &opclass);

		*fixed_indexquals = lappend(*fixed_indexquals, newclause);

		/*
		 * Look up the (possibly commuted) operator in the operator class to
		 * get its strategy numbers and the recheck indicator.	This also
		 * double-checks that we found an operator matching the index.
		 */
		get_op_opclass_properties(newclause->opno, opclass,
								  &stratno, &stratsubtype, &recheck);

		*indexstrategy = lappend_int(*indexstrategy, stratno);
		*indexsubtype = lappend_oid(*indexsubtype, stratsubtype);

		/* If it's not lossy, add to nonlossy_indexquals */
		if (!recheck)
			*nonlossy_indexquals = lappend(*nonlossy_indexquals, rinfo);
	}
}

static Node *
fix_indexqual_operand(Node *node, IndexOptInfo *index, Oid *opclass)
{
	/*
	 * We represent index keys by Var nodes having the varno of the base table
	 * but varattno equal to the index's attribute number (index column
	 * position).  This is a bit hokey ... would be cleaner to use a
	 * special-purpose node type that could not be mistaken for a regular Var.
	 * But it will do for now.
	 */
	Var		   *result;
	int			pos;
	ListCell   *indexpr_item;

	/*
	 * Remove any binary-compatible relabeling of the indexkey
	 */
	if (IsA(node, RelabelType))
		node = (Node *) ((RelabelType *) node)->arg;

	if (IsA(node, Var) &&
		((Var *) node)->varno == index->rel->relid)
	{
		/* Try to match against simple index columns */
		int			varatt = ((Var *) node)->varattno;

		if (varatt != 0)
		{
			for (pos = 0; pos < index->ncolumns; pos++)
			{
				if (index->indexkeys[pos] == varatt)
				{
					result = (Var *) copyObject(node);
					result->varattno = pos + 1;
					/* return the correct opclass, too */
					*opclass = index->classlist[pos];
					return (Node *) result;
				}
			}
		}
	}

	/* Try to match against index expressions */
	indexpr_item = list_head(index->indexprs);
	for (pos = 0; pos < index->ncolumns; pos++)
	{
		if (index->indexkeys[pos] == 0)
		{
			Node	   *indexkey;

			if (indexpr_item == NULL)
				elog(ERROR, "too few entries in indexprs list");
			indexkey = (Node *) lfirst(indexpr_item);
			if (indexkey && IsA(indexkey, RelabelType))
				indexkey = (Node *) ((RelabelType *) indexkey)->arg;
			if (equal(node, indexkey))
			{
				/* Found a match */
				result = makeVar(index->rel->relid, pos + 1,
								 exprType(lfirst(indexpr_item)), -1,
								 0);
				/* return the correct opclass, too */
				*opclass = index->classlist[pos];
				return (Node *) result;
			}
			indexpr_item = lnext(indexpr_item);
		}
	}

	/* Ooops... */
	elog(ERROR, "node is not an index attribute");
	*opclass = InvalidOid;		/* keep compiler quiet */
	return NULL;
}

/*
 * get_switched_clauses
 *	  Given a list of merge or hash joinclauses (as RestrictInfo nodes),
 *	  extract the bare clauses, and rearrange the elements within the
 *	  clauses, if needed, so the outer join variable is on the left and
 *	  the inner is on the right.  The original data structure is not touched;
 *	  a modified list is returned.
 */
static List *
get_switched_clauses(List *clauses, Relids outerrelids)
{
	List	   *t_list = NIL;
	ListCell   *l;

	foreach(l, clauses)
	{
		RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(l);
		OpExpr	   *clause = (OpExpr *) restrictinfo->clause;

		Assert(is_opclause(clause));
		if (bms_is_subset(restrictinfo->right_relids, outerrelids))
		{
			/*
			 * Duplicate just enough of the structure to allow commuting the
			 * clause without changing the original list.  Could use
			 * copyObject, but a complete deep copy is overkill.
			 */
			OpExpr	   *temp = makeNode(OpExpr);

			temp->opno = clause->opno;
			temp->opfuncid = InvalidOid;
			temp->opresulttype = clause->opresulttype;
			temp->opretset = clause->opretset;
			temp->args = list_copy(clause->args);
			/* Commute it --- note this modifies the temp node in-place. */
			CommuteClause(temp);
			t_list = lappend(t_list, temp);
		}
		else
			t_list = lappend(t_list, clause);
	}
	return t_list;
}

/*
 * order_qual_clauses
 *		Given a list of qual clauses that will all be evaluated at the same
 *		plan node, sort the list into the order we want to check the quals
 *		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.
 */
List *
order_qual_clauses(PlannerInfo *root, List *clauses)
{
	List	   *nosubplans;
	List	   *withsubplans;
	ListCell   *l;

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

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

		if (contain_subplans(clause))
			withsubplans = lappend(withsubplans, clause);
		else
			nosubplans = lappend(nosubplans, clause);
	}

	return list_concat(nosubplans, withsubplans);
}

/*
 * 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;