setrefs.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

								  rtable,
								  outer_itlist);
	}
	else if (IsA(inner_plan, BitmapAnd))
	{
		/* All we need do here is recurse */
		BitmapAnd  *innerscan = (BitmapAnd *) inner_plan;
		ListCell   *l;

		foreach(l, innerscan->bitmapplans)
		{
			set_inner_join_references((Plan *) lfirst(l),
									  rtable,
									  outer_itlist);
		}
	}
	else if (IsA(inner_plan, BitmapOr))
	{
		/* All we need do here is recurse */
		BitmapOr   *innerscan = (BitmapOr *) inner_plan;
		ListCell   *l;

		foreach(l, innerscan->bitmapplans)
		{
			set_inner_join_references((Plan *) lfirst(l),
									  rtable,
									  outer_itlist);
		}
	}
	else if (IsA(inner_plan, TidScan))
	{
		TidScan    *innerscan = (TidScan *) inner_plan;
		Index		innerrel = innerscan->scan.scanrelid;

		innerscan->tideval = join_references(innerscan->tideval,
											 rtable,
											 outer_itlist,
											 NULL,
											 innerrel);
	}
}

/*
 * set_uppernode_references
 *	  Update the targetlist and quals of an upper-level plan node
 *	  to refer to the tuples returned by its lefttree subplan.
 *
 * This is used for single-input plan types like Agg, Group, Result.
 *
 * In most cases, we have to match up individual Vars in the tlist and
 * qual expressions with elements of the subplan's tlist (which was
 * generated by flatten_tlist() from these selfsame expressions, so it
 * should have all the required variables).  There is an important exception,
 * however: GROUP BY and ORDER BY expressions will have been pushed into the
 * subplan tlist unflattened.  If these values are also needed in the output
 * then we want to reference the subplan tlist element rather than recomputing
 * the expression.
 */
static void
set_uppernode_references(Plan *plan, Index subvarno)
{
	Plan	   *subplan = plan->lefttree;
	indexed_tlist *subplan_itlist;
	List	   *output_targetlist;
	ListCell   *l;

	if (subplan != NULL)
		subplan_itlist = build_tlist_index(subplan->targetlist);
	else
		subplan_itlist = build_tlist_index(NIL);

	output_targetlist = NIL;
	foreach(l, plan->targetlist)
	{
		TargetEntry *tle = (TargetEntry *) lfirst(l);
		Node	   *newexpr;

		newexpr = replace_vars_with_subplan_refs((Node *) tle->expr,
												 subplan_itlist,
												 subvarno);
		tle = flatCopyTargetEntry(tle);
		tle->expr = (Expr *) newexpr;
		output_targetlist = lappend(output_targetlist, tle);
	}
	plan->targetlist = output_targetlist;

	plan->qual = (List *)
		replace_vars_with_subplan_refs((Node *) plan->qual,
									   subplan_itlist,
									   subvarno);

	pfree(subplan_itlist);
}

/*
 * build_tlist_index --- build an index data structure for a child tlist
 *
 * In most cases, subplan tlists will be "flat" tlists with only Vars,
 * so we try to optimize that case by extracting information about Vars
 * in advance.	Matching a parent tlist to a child is still an O(N^2)
 * operation, but at least with a much smaller constant factor than plain
 * tlist_member() searches.
 *
 * The result of this function is an indexed_tlist struct to pass to
 * search_indexed_tlist_for_var() or search_indexed_tlist_for_non_var().
 * When done, the indexed_tlist may be freed with a single pfree().
 */
static indexed_tlist *
build_tlist_index(List *tlist)
{
	indexed_tlist *itlist;
	tlist_vinfo *vinfo;
	ListCell   *l;

	/* Create data structure with enough slots for all tlist entries */
	itlist = (indexed_tlist *)
		palloc(offsetof(indexed_tlist, vars) +
			   list_length(tlist) * sizeof(tlist_vinfo));

	itlist->tlist = tlist;
	itlist->has_non_vars = false;

	/* Find the Vars and fill in the index array */
	vinfo = itlist->vars;
	foreach(l, tlist)
	{
		TargetEntry *tle = (TargetEntry *) lfirst(l);

		if (tle->expr && IsA(tle->expr, Var))
		{
			Var		   *var = (Var *) tle->expr;

			vinfo->varno = var->varno;
			vinfo->varattno = var->varattno;
			vinfo->resno = tle->resno;
			vinfo++;
		}
		else
			itlist->has_non_vars = true;
	}

	itlist->num_vars = (vinfo - itlist->vars);

	return itlist;
}

/*
 * search_indexed_tlist_for_var --- find a Var in an indexed tlist
 *
 * If a match is found, return a copy of the given Var with suitably
 * modified varno/varattno (to wit, newvarno and the resno of the TLE entry).
 * If no match, return NULL.
 */
static Var *
search_indexed_tlist_for_var(Var *var, indexed_tlist *itlist, Index newvarno)
{
	Index		varno = var->varno;
	AttrNumber	varattno = var->varattno;
	tlist_vinfo *vinfo;
	int			i;

	vinfo = itlist->vars;
	i = itlist->num_vars;
	while (i-- > 0)
	{
		if (vinfo->varno == varno && vinfo->varattno == varattno)
		{
			/* Found a match */
			Var		   *newvar = (Var *) copyObject(var);

			newvar->varno = newvarno;
			newvar->varattno = vinfo->resno;
			return newvar;
		}
		vinfo++;
	}
	return NULL;				/* no match */
}

/*
 * search_indexed_tlist_for_non_var --- find a non-Var in an indexed tlist
 *
 * If a match is found, return a Var constructed to reference the tlist item.
 * If no match, return NULL.
 *
 * NOTE: it is a waste of time to call this if !itlist->has_non_vars
 */
static Var *
search_indexed_tlist_for_non_var(Node *node,
								 indexed_tlist *itlist, Index newvarno)
{
	TargetEntry *tle;

	tle = tlist_member(node, itlist->tlist);
	if (tle)
	{
		/* Found a matching subplan output expression */
		Var		   *newvar;

		newvar = makeVar(newvarno,
						 tle->resno,
						 exprType((Node *) tle->expr),
						 exprTypmod((Node *) tle->expr),
						 0);
		newvar->varnoold = 0;	/* wasn't ever a plain Var */
		newvar->varoattno = 0;
		return newvar;
	}
	return NULL;				/* no match */
}

/*
 * join_references
 *	   Creates a new set of targetlist entries or join qual clauses by
 *	   changing the varno/varattno values of variables in the clauses
 *	   to reference target list values from the outer and inner join
 *	   relation target lists.
 *
 * This is used in two different scenarios: a normal join clause, where
 * all the Vars in the clause *must* be replaced by OUTER or INNER references;
 * and an indexscan being used on the inner side of a nestloop join.
 * In the latter case we want to replace the outer-relation Vars by OUTER
 * references, but not touch the Vars of the inner relation.
 *
 * For a normal join, acceptable_rel should be zero so that any failure to
 * match a Var will be reported as an error.  For the indexscan case,
 * pass inner_itlist = NULL and acceptable_rel = the ID of the inner relation.
 *
 * 'clauses' is the targetlist or list of join clauses
 * 'rtable' is the current range table
 * 'outer_itlist' is the indexed target list of the outer join relation
 * 'inner_itlist' is the indexed target list of the inner join relation,
 *		or NULL
 * 'acceptable_rel' is either zero or the rangetable index of a relation
 *		whose Vars may appear in the clause without provoking an error.
 *
 * Returns the new expression tree.  The original clause structure is
 * not modified.
 */
static List *
join_references(List *clauses,
				List *rtable,
				indexed_tlist *outer_itlist,
				indexed_tlist *inner_itlist,
				Index acceptable_rel)
{
	join_references_context context;

	context.rtable = rtable;
	context.outer_itlist = outer_itlist;
	context.inner_itlist = inner_itlist;
	context.acceptable_rel = acceptable_rel;
	return (List *) join_references_mutator((Node *) clauses, &context);
}

static Node *
join_references_mutator(Node *node,
						join_references_context *context)
{
	Var		   *newvar;

	if (node == NULL)
		return NULL;
	if (IsA(node, Var))
	{
		Var		   *var = (Var *) node;

		/* First look for the var in the input tlists */
		newvar = search_indexed_tlist_for_var(var,
											  context->outer_itlist,
											  OUTER);
		if (newvar)
			return (Node *) newvar;
		if (context->inner_itlist)
		{
			newvar = search_indexed_tlist_for_var(var,
												  context->inner_itlist,
												  INNER);
			if (newvar)
				return (Node *) newvar;
		}

		/* Return the Var unmodified, if it's for acceptable_rel */
		if (var->varno == context->acceptable_rel)
			return (Node *) copyObject(var);

		/* No referent found for Var */
		elog(ERROR, "variable not found in subplan target lists");
	}
	/* Try matching more complex expressions too, if tlists have any */
	if (context->outer_itlist->has_non_vars)
	{
		newvar = search_indexed_tlist_for_non_var(node,
												  context->outer_itlist,
												  OUTER);
		if (newvar)
			return (Node *) newvar;
	}
	if (context->inner_itlist && context->inner_itlist->has_non_vars)
	{
		newvar = search_indexed_tlist_for_non_var(node,
												  context->inner_itlist,
												  INNER);
		if (newvar)
			return (Node *) newvar;
	}
	return expression_tree_mutator(node,
								   join_references_mutator,
								   (void *) context);
}

/*
 * replace_vars_with_subplan_refs
 *		This routine modifies an expression tree so that all Var nodes
 *		reference target nodes of a subplan.  It is used to fix up
 *		target and qual expressions of non-join upper-level plan nodes.
 *
 * An error is raised if no matching var can be found in the subplan tlist
 * --- so this routine should only be applied to nodes whose subplans'
 * targetlists were generated via flatten_tlist() or some such method.
 *
 * If itlist->has_non_vars is true, then we try to match whole subexpressions
 * against elements of the subplan tlist, so that we can avoid recomputing
 * expressions that were already computed by the subplan.  (This is relatively
 * expensive, so we don't want to try it in the common case where the
 * subplan tlist is just a flattened list of Vars.)
 *
 * 'node': the tree to be fixed (a target item or qual)
 * 'subplan_itlist': indexed target list for subplan
 * 'subvarno': varno to be assigned to all Vars
 *
 * The resulting tree is a copy of the original in which all Var nodes have
 * varno = subvarno, varattno = resno of corresponding subplan target.
 * The original tree is not modified.
 */
static Node *
replace_vars_with_subplan_refs(Node *node,
							   indexed_tlist *subplan_itlist,
							   Index subvarno)
{
	replace_vars_with_subplan_refs_context context;

	context.subplan_itlist = subplan_itlist;
	context.subvarno = subvarno;
	return replace_vars_with_subplan_refs_mutator(node, &context);
}

static Node *
replace_vars_with_subplan_refs_mutator(Node *node,
							 replace_vars_with_subplan_refs_context *context)
{
	Var		   *newvar;

	if (node == NULL)
		return NULL;
	if (IsA(node, Var))
	{
		Var		   *var = (Var *) node;

		newvar = search_indexed_tlist_for_var(var,
											  context->subplan_itlist,
											  context->subvarno);
		if (!newvar)
			elog(ERROR, "variable not found in subplan target list");
		return (Node *) newvar;
	}
	/* Try matching more complex expressions too, if tlist has any */
	if (context->subplan_itlist->has_non_vars)
	{
		newvar = search_indexed_tlist_for_non_var(node,
												  context->subplan_itlist,
												  context->subvarno);
		if (newvar)
			return (Node *) newvar;
	}
	return expression_tree_mutator(node,
								   replace_vars_with_subplan_refs_mutator,
								   (void *) context);
}

/*****************************************************************************
 *					OPERATOR REGPROC LOOKUP
 *****************************************************************************/

/*
 * fix_opfuncids
 *	  Calculate opfuncid field from opno for each OpExpr node in given tree.
 *	  The given tree can be anything expression_tree_walker handles.
 *
 * The argument is modified in-place.  (This is OK since we'd want the
 * same change for any node, even if it gets visited more than once due to
 * shared structure.)
 */
void
fix_opfuncids(Node *node)
{
	/* This tree walk requires no special setup, so away we go... */
	fix_opfuncids_walker(node, NULL);
}

static bool
fix_opfuncids_walker(Node *node, void *context)
{
	if (node == NULL)
		return false;
	if (IsA(node, OpExpr))
		set_opfuncid((OpExpr *) node);
	else if (IsA(node, DistinctExpr))
		set_opfuncid((OpExpr *) node);	/* rely on struct equivalence */
	else if (IsA(node, ScalarArrayOpExpr))
		set_sa_opfuncid((ScalarArrayOpExpr *) node);
	else if (IsA(node, NullIfExpr))
		set_opfuncid((OpExpr *) node);	/* rely on struct equivalence */
	return expression_tree_walker(node, fix_opfuncids_walker, context);
}

/*
 * set_opfuncid
 *		Set the opfuncid (procedure OID) in an OpExpr node,
 *		if it hasn't been set already.
 *
 * Because of struct equivalence, this can also be used for
 * DistinctExpr and NullIfExpr nodes.
 */
void
set_opfuncid(OpExpr *opexpr)
{
	if (opexpr->opfuncid == InvalidOid)
		opexpr->opfuncid = get_opcode(opexpr->opno);
}

/*
 * set_sa_opfuncid
 *		As above, for ScalarArrayOpExpr nodes.
 */
static void
set_sa_opfuncid(ScalarArrayOpExpr *opexpr)
{
	if (opexpr->opfuncid == InvalidOid)
		opexpr->opfuncid = get_opcode(opexpr->opno);
}