createplan.c

PostgreSQL7.4.6 for Linux

		}
	}

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

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

	join_plan = make_nestloop(tlist,
							  joinclauses,
							  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(Query *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 = set_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(Query *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;
	List	   *innerhashkeys;
	List	   *hcl;

	/* 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 = set_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);

	/*
	 * Extract the inner hash keys (right-hand operands of the hashclauses)
	 * to put in the Hash node.  Must do a deep copy in case there are
	 * subplans in the hash keys.
	 */
	innerhashkeys = NIL;
	foreach(hcl, hashclauses)
		innerhashkeys = lappend(innerhashkeys,
								copyObject(get_rightop(lfirst(hcl))));

	/* 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->targetlist,
						  innerhashkeys,
						  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_indxqual_references
 *	  Adjust indexqual clauses to the form the executor's indexqual
 *	  machinery needs, and check for recheckable (lossy) index conditions.
 *
 * We have three tasks here:
 *	* 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.  (Someday the executor might not need this, but for now it does.)
 *	* If the indexable operator is marked 'amopreqcheck' in pg_amop, then
 *	  the index is "lossy" for this operator: it may return more tuples than
 *	  actually satisfy the operator condition.	For each such operator, we
 *	  must add (the original form of) the indexqual clause to the "qpquals"
 *	  of the indexscan node, where the operator will be re-evaluated to
 *	  ensure it passes.
 *
 * This code used to be entirely bogus for multi-index scans.  Now it keeps
 * track of which index applies to each subgroup of index qual clauses...
 *
 * Both the input list and the output lists have the form of lists of sublists
 * of qual clauses --- the top-level list has one entry for each indexscan
 * to be performed.  The semantics are OR-of-ANDs.
 *
 * fixed_indexquals receives a modified copy of the indexqual 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).
 *
 * recheck_indexquals similarly receives a full copy of whichever clauses
 * need rechecking.
 */
static void
fix_indxqual_references(List *indexquals, IndexPath *index_path,
					  List **fixed_indexquals, List **recheck_indexquals)
{
	FastList	fixed_quals;
	FastList	recheck_quals;
	Relids		baserelids = index_path->path.parent->relids;
	int			baserelid = index_path->path.parent->relid;
	List	   *ixinfo = index_path->indexinfo;
	List	   *i;

	FastListInit(&fixed_quals);
	FastListInit(&recheck_quals);
	foreach(i, indexquals)
	{
		List	   *indexqual = lfirst(i);
		IndexOptInfo *index = (IndexOptInfo *) lfirst(ixinfo);
		List	   *fixed_qual;
		List	   *recheck_qual;

		fix_indxqual_sublist(indexqual, baserelids, baserelid, index,
							 &fixed_qual, &recheck_qual);
		FastAppend(&fixed_quals, fixed_qual);
		if (recheck_qual != NIL)
			FastAppend(&recheck_quals, recheck_qual);

		ixinfo = lnext(ixinfo);
	}

	*fixed_indexquals = FastListValue(&fixed_quals);
	*recheck_indexquals = FastListValue(&recheck_quals);
}

/*
 * Fix the sublist of indexquals to be used in a particular scan.
 *
 * 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.)	Also change the operator if necessary, and check for
 * lossy index behavior.
 *
 * Returns two lists: the list of fixed indexquals, and the list (usually
 * empty) of original clauses that must be rechecked as qpquals because
 * the index is lossy for this operator type.
 */
static void
fix_indxqual_sublist(List *indexqual,
					 Relids baserelids, int baserelid,
					 IndexOptInfo *index,
					 List **fixed_quals, List **recheck_quals)
{
	FastList	fixed_qual;
	FastList	recheck_qual;
	List	   *i;

	FastListInit(&fixed_qual);
	FastListInit(&recheck_qual);
	foreach(i, indexqual)
	{
		OpExpr	   *clause = (OpExpr *) lfirst(i);
		OpExpr	   *newclause;
		Relids		leftvarnos;
		Oid			opclass;

		if (!IsA(clause, OpExpr) ||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.
		 */
		leftvarnos = pull_varnos((Node *) lfirst(newclause->args));
		if (!bms_equal(leftvarnos, baserelids))
			CommuteClause(newclause);
		bms_free(leftvarnos);

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

		FastAppend(&fixed_qual, newclause);

		/*
		 * Finally, check to see if index is lossy for this operator. If
		 * so, add (a copy of) original form of clause to recheck list.
		 */
		if (op_requires_recheck(newclause->opno, opclass))
			FastAppend(&recheck_qual, copyObject((Node *) clause));
	}

	*fixed_quals = FastListValue(&fixed_qual);
	*recheck_quals = FastListValue(&recheck_qual);
}

static Node *
fix_indxqual_operand(Node *node, int baserelid, 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;
	List	   *indexprs;

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

	if (IsA(node, Var) &&
		((Var *) node)->varno == baserelid)
	{
		/* 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 */
	indexprs = index->indexprs;
	for (pos = 0; pos < index->ncolumns; pos++)
	{
		if (index->indexkeys[pos] == 0)
		{
			Node	   *indexkey;

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

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

/*
 * 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;
	List	   *i;

	foreach(i, clauses)
	{
		RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(i);
		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 = listCopy(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