subselect.c

来自「PostgreSQL7.4.6 for Linux」· C语言 代码 · 共 1,118 行 · 第 1/3 页

	 * ininfo->sub_targetlist is filled with a list of Vars
	 * representing the subselect outputs.
	 */
	exprs = convert_sublink_opers(sublink->lefthand,
								  sublink->operOids,
								  subselect->targetList,
								  rtindex,
								  &ininfo->sub_targetlist);
	return (Node *) make_ands_explicit(exprs);
}

/*
 * Replace correlation vars (uplevel vars) with Params.
 *
 * Uplevel aggregates are replaced, too.
 *
 * Note: it is critical that this runs immediately after SS_process_sublinks.
 * Since we do not recurse into the arguments of uplevel aggregates, they will
 * get copied to the appropriate subplan args list in the parent query with
 * uplevel vars not replaced by Params, but only adjusted in level (see
 * replace_outer_agg).	That's exactly what we want for the vars of the parent
 * level --- but if an aggregate's argument contains any further-up variables,
 * they have to be replaced with Params in their turn.	That will happen when
 * the parent level runs SS_replace_correlation_vars.  Therefore it must do
 * so after expanding its sublinks to subplans.  And we don't want any steps
 * in between, else those steps would never get applied to the aggregate
 * argument expressions, either in the parent or the child level.
 */
Node *
SS_replace_correlation_vars(Node *expr)
{
	/* No setup needed for tree walk, so away we go */
	return replace_correlation_vars_mutator(expr, NULL);
}

static Node *
replace_correlation_vars_mutator(Node *node, void *context)
{
	if (node == NULL)
		return NULL;
	if (IsA(node, Var))
	{
		if (((Var *) node)->varlevelsup > 0)
			return (Node *) replace_outer_var((Var *) node);
	}
	if (IsA(node, Aggref))
	{
		if (((Aggref *) node)->agglevelsup > 0)
			return (Node *) replace_outer_agg((Aggref *) node);
	}
	return expression_tree_mutator(node,
								   replace_correlation_vars_mutator,
								   context);
}

/*
 * Expand SubLinks to SubPlans in the given expression.
 *
 * The isQual argument tells whether or not this expression is a WHERE/HAVING
 * qualifier expression.  If it is, any sublinks appearing at top level need
 * not distinguish FALSE from UNKNOWN return values.
 */
Node *
SS_process_sublinks(Node *expr, bool isQual)
{
	/* The only context needed is the initial are-we-in-a-qual flag */
	return process_sublinks_mutator(expr, &isQual);
}

static Node *
process_sublinks_mutator(Node *node, bool *isTopQual)
{
	bool		locTopQual;

	if (node == NULL)
		return NULL;
	if (IsA(node, SubLink))
	{
		SubLink    *sublink = (SubLink *) node;
		List	   *lefthand;

		/*
		 * First, recursively process the lefthand-side expressions, if
		 * any.
		 */
		locTopQual = false;
		lefthand = (List *)
			process_sublinks_mutator((Node *) sublink->lefthand, &locTopQual);

		/*
		 * Now build the SubPlan node and make the expr to return.
		 */
		return make_subplan(sublink, lefthand, *isTopQual);
	}

	/*
	 * We should never see a SubPlan expression in the input (since this
	 * is the very routine that creates 'em to begin with).  We shouldn't
	 * find ourselves invoked directly on a Query, either.
	 */
	Assert(!is_subplan(node));
	Assert(!IsA(node, Query));

	/*
	 * If we recurse down through anything other than a List node, we are
	 * definitely not at top qual level anymore.
	 */
	if (IsA(node, List))
		locTopQual = *isTopQual;
	else
		locTopQual = false;

	return expression_tree_mutator(node,
								   process_sublinks_mutator,
								   (void *) &locTopQual);
}

/*
 * SS_finalize_plan - do final sublink processing for a completed Plan.
 *
 * This recursively computes the extParam and allParam sets
 * for every Plan node in the given plan tree.
 */
void
SS_finalize_plan(Plan *plan, List *rtable)
{
	Bitmapset  *outer_params = NULL;
	Bitmapset  *valid_params = NULL;
	int			paramid;
	List	   *lst;

	/*
	 * First, scan the param list to discover the sets of params that are
	 * available from outer query levels and my own query level. We do
	 * this once to save time in the per-plan recursion steps.
	 */
	paramid = 0;
	foreach(lst, PlannerParamList)
	{
		PlannerParamItem *pitem = (PlannerParamItem *) lfirst(lst);

		if (pitem->abslevel < PlannerQueryLevel)
		{
			/* valid outer-level parameter */
			outer_params = bms_add_member(outer_params, paramid);
			valid_params = bms_add_member(valid_params, paramid);
		}
		else if (pitem->abslevel == PlannerQueryLevel &&
				 IsA(pitem->item, Param))
		{
			/* valid local parameter (i.e., a setParam of my child) */
			valid_params = bms_add_member(valid_params, paramid);
		}

		paramid++;
	}

	/*
	 * Now recurse through plan tree.
	 */
	(void) finalize_plan(plan, rtable, outer_params, valid_params);

	bms_free(outer_params);
	bms_free(valid_params);
}

/*
 * Recursive processing of all nodes in the plan tree
 *
 * The return value is the computed allParam set for the given Plan node.
 * This is just an internal notational convenience.
 */
static Bitmapset *
finalize_plan(Plan *plan, List *rtable,
			  Bitmapset *outer_params, Bitmapset *valid_params)
{
	finalize_primnode_context context;
	List	   *lst;

	if (plan == NULL)
		return NULL;

	context.paramids = NULL;	/* initialize set to empty */
	context.outer_params = outer_params;

	/*
	 * When we call finalize_primnode, context.paramids sets are
	 * automatically merged together.  But when recursing to self, we have
	 * to do it the hard way.  We want the paramids set to include params
	 * in subplans as well as at this level.
	 */

	/* Find params in targetlist and qual */
	finalize_primnode((Node *) plan->targetlist, &context);
	finalize_primnode((Node *) plan->qual, &context);

	/* Check additional node-type-specific fields */
	switch (nodeTag(plan))
	{
		case T_Result:
			finalize_primnode(((Result *) plan)->resconstantqual,
							  &context);
			break;

		case T_IndexScan:
			finalize_primnode((Node *) ((IndexScan *) plan)->indxqual,
							  &context);

			/*
			 * we need not look at indxqualorig, since it will have the
			 * same param references as indxqual.
			 */
			break;

		case T_TidScan:
			finalize_primnode((Node *) ((TidScan *) plan)->tideval,
							  &context);
			break;

		case T_SubqueryScan:

			/*
			 * In a SubqueryScan, SS_finalize_plan has already been run on
			 * the subplan by the inner invocation of subquery_planner, so
			 * there's no need to do it again.  Instead, just pull out the
			 * subplan's extParams list, which represents the params it
			 * needs from my level and higher levels.
			 */
			context.paramids = bms_add_members(context.paramids,
							 ((SubqueryScan *) plan)->subplan->extParam);
			break;

		case T_FunctionScan:
			{
				RangeTblEntry *rte;

				rte = rt_fetch(((FunctionScan *) plan)->scan.scanrelid,
							   rtable);
				Assert(rte->rtekind == RTE_FUNCTION);
				finalize_primnode(rte->funcexpr, &context);
			}
			break;

		case T_Append:
			foreach(lst, ((Append *) plan)->appendplans)
			{
				context.paramids =
					bms_add_members(context.paramids,
									finalize_plan((Plan *) lfirst(lst),
												  rtable,
												  outer_params,
												  valid_params));
			}
			break;

		case T_NestLoop:
			finalize_primnode((Node *) ((Join *) plan)->joinqual,
							  &context);
			break;

		case T_MergeJoin:
			finalize_primnode((Node *) ((Join *) plan)->joinqual,
							  &context);
			finalize_primnode((Node *) ((MergeJoin *) plan)->mergeclauses,
							  &context);
			break;

		case T_HashJoin:
			finalize_primnode((Node *) ((Join *) plan)->joinqual,
							  &context);
			finalize_primnode((Node *) ((HashJoin *) plan)->hashclauses,
							  &context);
			break;

		case T_Limit:
			finalize_primnode(((Limit *) plan)->limitOffset,
							  &context);
			finalize_primnode(((Limit *) plan)->limitCount,
							  &context);
			break;

		case T_Hash:
			finalize_primnode((Node *) ((Hash *) plan)->hashkeys,
							  &context);
			break;

		case T_Agg:
		case T_SeqScan:
		case T_Material:
		case T_Sort:
		case T_Unique:
		case T_SetOp:
		case T_Group:
			break;

		default:
			elog(ERROR, "unrecognized node type: %d",
				 (int) nodeTag(plan));
	}

	/* Process left and right child plans, if any */
	context.paramids = bms_add_members(context.paramids,
									   finalize_plan(plan->lefttree,
													 rtable,
													 outer_params,
													 valid_params));

	context.paramids = bms_add_members(context.paramids,
									   finalize_plan(plan->righttree,
													 rtable,
													 outer_params,
													 valid_params));

	/* Now we have all the paramids */

	if (!bms_is_subset(context.paramids, valid_params))
		elog(ERROR, "plan should not reference subplan's variable");

	plan->extParam = bms_intersect(context.paramids, outer_params);
	plan->allParam = context.paramids;

	/*
	 * For speed at execution time, make sure extParam/allParam are
	 * actually NULL if they are empty sets.
	 */
	if (bms_is_empty(plan->extParam))
	{
		bms_free(plan->extParam);
		plan->extParam = NULL;
	}
	if (bms_is_empty(plan->allParam))
	{
		bms_free(plan->allParam);
		plan->allParam = NULL;
	}

	return plan->allParam;
}

/*
 * finalize_primnode: add IDs of all PARAM_EXEC params appearing in the given
 * expression tree to the result set.
 */
static bool
finalize_primnode(Node *node, finalize_primnode_context *context)
{
	if (node == NULL)
		return false;
	if (IsA(node, Param))
	{
		if (((Param *) node)->paramkind == PARAM_EXEC)
		{
			int			paramid = (int) ((Param *) node)->paramid;

			context->paramids = bms_add_member(context->paramids, paramid);
		}
		return false;			/* no more to do here */
	}
	if (is_subplan(node))
	{
		SubPlan    *subplan = (SubPlan *) node;

		/* Add outer-level params needed by the subplan to paramids */
		context->paramids = bms_join(context->paramids,
								   bms_intersect(subplan->plan->extParam,
												 context->outer_params));
		/* fall through to recurse into subplan args */
	}
	return expression_tree_walker(node, finalize_primnode,
								  (void *) context);
}