planner.c

关系型数据库 Postgresql 6.5.2

	extravars = nconc(extravars, pull_var_clause(parse->havingQual));

	foreach(gl, extravars)
	{
		Var		   *v = (Var *) lfirst(gl);

		if (tlist_member(v, sub_tlist) == NULL)
		{

			/*
			 * Make sure sub_tlist element is a fresh object not shared
			 * with any other structure; not sure if anything will break
			 * if it is shared, but better to be safe...
			 */
			sub_tlist = lappend(sub_tlist,
								create_tl_element((Var *) copyObject(v),
												  next_resno));
			next_resno++;
		}
	}

	return sub_tlist;
}

static Plan *
make_groupplan(List *group_tlist,
			   bool tuplePerGroup,
			   List *groupClause,
			   AttrNumber *grpColIdx,
			   Plan *subplan)
{
	List	   *sort_tlist;
	List	   *sl;
	Sort	   *sortplan;
	Group	   *grpplan;
	int			numCols = length(groupClause);

	/*
	 * Make the targetlist for the Sort node; it always just references
	 * each of the corresponding target items of the subplan.  We need to
	 * ensure that simple Vars in the subplan's target list are
	 * recognizable by replace_vars_with_subplan_refs when it's applied to
	 * the Sort/Group target list, so copy up their varnoold/varoattno.
	 */
	sort_tlist = NIL;
	foreach(sl, subplan->targetlist)
	{
		TargetEntry *te = (TargetEntry *) lfirst(sl);
		Resdom	   *resdom = te->resdom;
		Var		   *newvar;

		if (IsA(te->expr, Var))
		{
			Var		   *subvar = (Var *) te->expr;

			newvar = makeVar(1, resdom->resno,
							 resdom->restype, resdom->restypmod,
							 0, subvar->varnoold, subvar->varoattno);
		}
		else
		{
			newvar = makeVar(1, resdom->resno,
							 resdom->restype, resdom->restypmod,
							 0, -1, resdom->resno);
		}

		sort_tlist = lappend(sort_tlist,
						   makeTargetEntry((Resdom *) copyObject(resdom),
										   (Node *) newvar));
	}

	/*
	 * Make the Sort node
	 */
	sortplan = make_sort(sort_tlist,
						 _NONAME_RELATION_ID_,
						 subplan,
						 numCols);
	sortplan->plan.cost = subplan->cost;		/* XXX assume no cost */

	/*
	 * If the caller gave us a target list, use it after fixing the
	 * variables. If not, we need the same sort of "repeater" tlist as for
	 * the Sort node.
	 */
	if (group_tlist)
	{
		group_tlist = copyObject(group_tlist);	/* necessary?? */
		replace_tlist_with_subplan_refs(group_tlist,
										(Index) 0,
										subplan->targetlist);
	}
	else
		group_tlist = copyObject(sort_tlist);

	/*
	 * Make the Group node
	 */
	grpplan = make_group(group_tlist, tuplePerGroup, numCols,
						 grpColIdx, sortplan);

	return (Plan *) grpplan;
}

/*
 * make_sortplan
 *	  Returns a sortplan which is basically a SORT node attached to the
 *	  top of the plan returned from the planner.  It also adds the
 *	   cost of sorting into the plan.
 *
 * sortkeys: ( resdom1 resdom2 resdom3 ...)
 * sortops:  (sortop1 sortop2 sortop3 ...)
 */
static Plan *
make_sortplan(List *tlist, List *sortcls, Plan *plannode)
{
	Plan	   *sortplan = (Plan *) NULL;
	List	   *temp_tlist = NIL;
	List	   *i = NIL;
	Resdom	   *resnode = (Resdom *) NULL;
	Resdom	   *resdom = (Resdom *) NULL;
	int			keyno = 1;

	/*
	 * First make a copy of the tlist so that we don't corrupt the the
	 * original .
	 */

	temp_tlist = new_unsorted_tlist(tlist);

	foreach(i, sortcls)
	{
		SortClause *sortcl = (SortClause *) lfirst(i);

		resnode = sortcl->resdom;
		resdom = tlist_resdom(temp_tlist, resnode);

		/*
		 * Order the resdom keys and replace the operator OID for each key
		 * with the regproc OID.
		 */
		resdom->reskey = keyno;
		resdom->reskeyop = get_opcode(sortcl->opoid);
		keyno += 1;
	}

	sortplan = (Plan *) make_sort(temp_tlist,
								  _NONAME_RELATION_ID_,
								  (Plan *) plannode,
								  length(sortcls));

	/*
	 * XXX Assuming that an internal sort has no. cost. This is wrong, but
	 * given that at this point, we don't know the no. of tuples returned,
	 * etc, we can't do better than to add a constant cost. This will be
	 * fixed once we move the sort further into the planner, but for now
	 * ... functionality....
	 */

	sortplan->cost = plannode->cost;

	return sortplan;
}

/*
 * pg_checkretval() -- check return value of a list of sql parse
 *						trees.
 *
 * The return value of a sql function is the value returned by
 * the final query in the function.  We do some ad-hoc define-time
 * type checking here to be sure that the user is returning the
 * type he claims.
 *
 * XXX Why is this function in this module?
 */
void
pg_checkretval(Oid rettype, List *queryTreeList)
{
	Query	   *parse;
	List	   *tlist;
	List	   *rt;
	int			cmd;
	Type		typ;
	Resdom	   *resnode;
	Relation	reln;
	Oid			relid;
	Oid			tletype;
	int			relnatts;
	int			i;

	/* find the final query */
	parse = (Query *) nth(length(queryTreeList) - 1, queryTreeList);

	/*
	 * test 1:	if the last query is a utility invocation, then there had
	 * better not be a return value declared.
	 */
	if (parse->commandType == CMD_UTILITY)
	{
		if (rettype == InvalidOid)
			return;
		else
			elog(ERROR, "return type mismatch in function decl: final query is a catalog utility");
	}

	/* okay, it's an ordinary query */
	tlist = parse->targetList;
	rt = parse->rtable;
	cmd = parse->commandType;

	/*
	 * test 2:	if the function is declared to return no value, then the
	 * final query had better not be a retrieve.
	 */
	if (rettype == InvalidOid)
	{
		if (cmd == CMD_SELECT)
			elog(ERROR,
				 "function declared with no return type, but final query is a retrieve");
		else
			return;
	}

	/* by here, the function is declared to return some type */
	if ((typ = typeidType(rettype)) == NULL)
		elog(ERROR, "can't find return type %u for function\n", rettype);

	/*
	 * test 3:	if the function is declared to return a value, then the
	 * final query had better be a retrieve.
	 */
	if (cmd != CMD_SELECT)
		elog(ERROR, "function declared to return type %s, but final query is not a retrieve", typeTypeName(typ));

	/*
	 * test 4:	for base type returns, the target list should have exactly
	 * one entry, and its type should agree with what the user declared.
	 */

	if (typeTypeRelid(typ) == InvalidOid)
	{
		if (ExecTargetListLength(tlist) > 1)
			elog(ERROR, "function declared to return %s returns multiple values in final retrieve", typeTypeName(typ));

		resnode = (Resdom *) ((TargetEntry *) lfirst(tlist))->resdom;
		if (resnode->restype != rettype)
			elog(ERROR, "return type mismatch in function: declared to return %s, returns %s", typeTypeName(typ), typeidTypeName(resnode->restype));

		/* by here, base return types match */
		return;
	}

	/*
	 * If the target list is of length 1, and the type of the varnode in
	 * the target list is the same as the declared return type, this is
	 * okay.  This can happen, for example, where the body of the function
	 * is 'retrieve (x = func2())', where func2 has the same return type
	 * as the function that's calling it.
	 */
	if (ExecTargetListLength(tlist) == 1)
	{
		resnode = (Resdom *) ((TargetEntry *) lfirst(tlist))->resdom;
		if (resnode->restype == rettype)
			return;
	}

	/*
	 * By here, the procedure returns a (set of) tuples.  This part of the
	 * typechecking is a hack.	We look up the relation that is the
	 * declared return type, and be sure that attributes 1 .. n in the
	 * target list match the declared types.
	 */
	reln = heap_open(typeTypeRelid(typ));

	if (!RelationIsValid(reln))
		elog(ERROR, "cannot open relation relid %u", typeTypeRelid(typ));

	relid = reln->rd_id;
	relnatts = reln->rd_rel->relnatts;

	if (ExecTargetListLength(tlist) != relnatts)
		elog(ERROR, "function declared to return type %s does not retrieve (%s.*)", typeTypeName(typ), typeTypeName(typ));

	/* expect attributes 1 .. n in order */
	for (i = 1; i <= relnatts; i++)
	{
		TargetEntry *tle = lfirst(tlist);
		Node	   *thenode = tle->expr;

		tlist = lnext(tlist);
		tletype = exprType(thenode);

#ifdef NOT_USED					/* fix me */
		/* this is tedious */
		if (IsA(thenode, Var))
			tletype = (Oid) ((Var *) thenode)->vartype;
		else if (IsA(thenode, Const))
			tletype = (Oid) ((Const *) thenode)->consttype;
		else if (IsA(thenode, Param))
			tletype = (Oid) ((Param *) thenode)->paramtype;
		else if (IsA(thenode, Expr))
			tletype = Expr;

		else if (IsA(thenode, LispList))
		{
			thenode = lfirst(thenode);
			if (IsA(thenode, Oper))
				tletype = (Oid) get_opresulttype((Oper *) thenode);
			else if (IsA(thenode, Func))
				tletype = (Oid) get_functype((Func *) thenode);
			else
				elog(ERROR, "function declared to return type %s does not retrieve (%s.all)", typeTypeName(typ), typeTypeName(typ));
		}
		else
			elog(ERROR, "function declared to return type %s does not retrieve (%s.all)", typeTypeName(typ), typeTypeName(typ));
#endif
		/* reach right in there, why don't you? */
		if (tletype != reln->rd_att->attrs[i - 1]->atttypid)
			elog(ERROR, "function declared to return type %s does not retrieve (%s.all)", typeTypeName(typ), typeTypeName(typ));
	}

	heap_close(reln);

	/* success */
	return;
}


/* ----------
 * Support function for need_sortplan
 * ----------
 */
static TargetEntry *
get_matching_tle(Plan *plan, Resdom *resdom)
{
	List	   *i;
	TargetEntry *tle;

	foreach(i, plan->targetlist)
	{
		tle = (TargetEntry *) lfirst(i);
		if (tle->resdom->resno == resdom->resno)
			return tle;
	}
	return NULL;
}


/* ----------
 * Check if a user requested ORDER BY is already satisfied by
 * the choosen index scan.
 *
 * Returns TRUE if sort is required, FALSE if can be omitted.
 * ----------
 */
static bool
need_sortplan(List *sortcls, Plan *plan)
{
	Relation	indexRel;
	IndexScan  *indexScan;
	Oid			indexId;
	List	   *i;
	HeapTuple	htup;
	Form_pg_index index_tup;
	int			key_no = 0;

	/* ----------
	 * Must be an IndexScan
	 * ----------
	 */
	if (nodeTag(plan) != T_IndexScan)
		return TRUE;

	indexScan = (IndexScan *) plan;

	/* ----------
	 * Should not have left- or righttree
	 * ----------
	 */
	if (plan->lefttree != NULL)
		return TRUE;
	if (plan->righttree != NULL)
		return TRUE;

	/* ----------
	 * Must be a single index scan
	 * ----------
	 */
	if (length(indexScan->indxid) != 1)
		return TRUE;

	/* ----------
	 * Indices can only have up to 8 attributes. So an ORDER BY using
	 * more that 8 attributes could never be satisfied by an index.
	 * ----------
	 */
	if (length(sortcls) > 8)
		return TRUE;

	/* ----------
	 * The choosen Index must be a btree
	 * ----------
	 */
	indexId = lfirsti(indexScan->indxid);

	indexRel = index_open(indexId);
	if (strcmp(nameout(&(indexRel->rd_am->amname)), "btree") != 0)
	{
		heap_close(indexRel);
		return TRUE;
	}
	heap_close(indexRel);

	/* ----------
	 * Fetch the index tuple
	 * ----------
	 */
	htup = SearchSysCacheTuple(INDEXRELID,
							   ObjectIdGetDatum(indexId), 0, 0, 0);
	if (!HeapTupleIsValid(htup))
		elog(ERROR, "cache lookup for index %u failed", indexId);
	index_tup = (Form_pg_index) GETSTRUCT(htup);

	/* ----------
	 * Check if all the sort clauses match the attributes in the index
	 * ----------
	 */
	foreach(i, sortcls)
	{
		SortClause *sortcl;
		Resdom	   *resdom;
		TargetEntry *tle;
		Var		   *var;

		sortcl = (SortClause *) lfirst(i);

		resdom = sortcl->resdom;
		tle = get_matching_tle(plan, resdom);
		if (tle == NULL)
		{
			/* ----------
			 * Could this happen?
			 * ----------
			 */
			return TRUE;
		}
		if (nodeTag(tle->expr) != T_Var)
		{
			/* ----------
			 * The target list expression isn't a var, so it
			 * cannot be the indexed attribute
			 * ----------
			 */
			return TRUE;
		}
		var = (Var *) (tle->expr);

		if (var->varno != indexScan->scan.scanrelid)
		{
			/* ----------
			 * This Var isn't from the scan relation. So it isn't
			 * that of the index
			 * ----------
			 */
			return TRUE;
		}

		if (var->varattno != index_tup->indkey[key_no])
		{
			/* ----------
			 * It isn't the indexed attribute.
			 * ----------
			 */
			return TRUE;
		}

		if (oprid(oper("<", resdom->restype, resdom->restype, FALSE)) != sortcl->opoid)
		{
			/* ----------
			 * Sort order isn't in ascending order.
			 * ----------
			 */
			return TRUE;
		}

		key_no++;
	}

	/* ----------
	 * Index matches ORDER BY - sort not required
	 * ----------
	 */
	return FALSE;
}