rewritemanip.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

/*-------------------------------------------------------------------------
 *
 * rewriteManip.c
 *
 * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/rewrite/rewriteManip.c,v 1.92.2.3 2006/01/06 20:11:18 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "catalog/pg_type.h"
#include "nodes/makefuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/tlist.h"
#include "parser/parsetree.h"
#include "parser/parse_coerce.h"
#include "parser/parse_relation.h"
#include "rewrite/rewriteManip.h"
#include "utils/lsyscache.h"


typedef struct
{
	int			sublevels_up;
} checkExprHasAggs_context;

static bool checkExprHasAggs_walker(Node *node,
						checkExprHasAggs_context *context);
static bool checkExprHasSubLink_walker(Node *node, void *context);
static Relids offset_relid_set(Relids relids, int offset);
static Relids adjust_relid_set(Relids relids, int oldrelid, int newrelid);


/*
 * checkExprHasAggs -
 *	Check if an expression contains an aggregate function call.
 *
 * The objective of this routine is to detect whether there are aggregates
 * belonging to the initial query level.  Aggregates belonging to subqueries
 * or outer queries do NOT cause a true result.  We must recurse into
 * subqueries to detect outer-reference aggregates that logically belong to
 * the initial query level.
 */
bool
checkExprHasAggs(Node *node)
{
	checkExprHasAggs_context context;

	context.sublevels_up = 0;

	/*
	 * Must be prepared to start with a Query or a bare expression tree; if
	 * it's a Query, we don't want to increment sublevels_up.
	 */
	return query_or_expression_tree_walker(node,
										   checkExprHasAggs_walker,
										   (void *) &context,
										   0);
}

static bool
checkExprHasAggs_walker(Node *node, checkExprHasAggs_context *context)
{
	if (node == NULL)
		return false;
	if (IsA(node, Aggref))
	{
		if (((Aggref *) node)->agglevelsup == context->sublevels_up)
			return true;		/* abort the tree traversal and return true */
		/* else fall through to examine argument */
	}
	if (IsA(node, Query))
	{
		/* Recurse into subselects */
		bool		result;

		context->sublevels_up++;
		result = query_tree_walker((Query *) node,
								   checkExprHasAggs_walker,
								   (void *) context, 0);
		context->sublevels_up--;
		return result;
	}
	return expression_tree_walker(node, checkExprHasAggs_walker,
								  (void *) context);
}

/*
 * checkExprHasSubLink -
 *	Check if an expression contains a SubLink.
 */
bool
checkExprHasSubLink(Node *node)
{
	/*
	 * If a Query is passed, examine it --- but we need not recurse into
	 * sub-Queries.
	 */
	return query_or_expression_tree_walker(node,
										   checkExprHasSubLink_walker,
										   NULL,
										   QTW_IGNORE_RT_SUBQUERIES);
}

static bool
checkExprHasSubLink_walker(Node *node, void *context)
{
	if (node == NULL)
		return false;
	if (IsA(node, SubLink))
		return true;			/* abort the tree traversal and return true */
	return expression_tree_walker(node, checkExprHasSubLink_walker, context);
}


/*
 * OffsetVarNodes - adjust Vars when appending one query's RT to another
 *
 * Find all Var nodes in the given tree with varlevelsup == sublevels_up,
 * and increment their varno fields (rangetable indexes) by 'offset'.
 * The varnoold fields are adjusted similarly.	Also, adjust other nodes
 * that contain rangetable indexes, such as RangeTblRef and JoinExpr.
 *
 * NOTE: although this has the form of a walker, we cheat and modify the
 * nodes in-place.	The given expression tree should have been copied
 * earlier to ensure that no unwanted side-effects occur!
 */

typedef struct
{
	int			offset;
	int			sublevels_up;
} OffsetVarNodes_context;

static bool
OffsetVarNodes_walker(Node *node, OffsetVarNodes_context *context)
{
	if (node == NULL)
		return false;
	if (IsA(node, Var))
	{
		Var		   *var = (Var *) node;

		if (var->varlevelsup == context->sublevels_up)
		{
			var->varno += context->offset;
			var->varnoold += context->offset;
		}
		return false;
	}
	if (IsA(node, RangeTblRef))
	{
		RangeTblRef *rtr = (RangeTblRef *) node;

		if (context->sublevels_up == 0)
			rtr->rtindex += context->offset;
		/* the subquery itself is visited separately */
		return false;
	}
	if (IsA(node, JoinExpr))
	{
		JoinExpr   *j = (JoinExpr *) node;

		if (context->sublevels_up == 0)
			j->rtindex += context->offset;
		/* fall through to examine children */
	}
	if (IsA(node, InClauseInfo))
	{
		InClauseInfo *ininfo = (InClauseInfo *) node;

		if (context->sublevels_up == 0)
		{
			ininfo->lefthand = offset_relid_set(ininfo->lefthand,
												context->offset);
			ininfo->righthand = offset_relid_set(ininfo->righthand,
												 context->offset);
		}
		/* fall through to examine children */
	}
	if (IsA(node, Query))
	{
		/* Recurse into subselects */
		bool		result;

		context->sublevels_up++;
		result = query_tree_walker((Query *) node, OffsetVarNodes_walker,
								   (void *) context, 0);
		context->sublevels_up--;
		return result;
	}
	return expression_tree_walker(node, OffsetVarNodes_walker,
								  (void *) context);
}

void
OffsetVarNodes(Node *node, int offset, int sublevels_up)
{
	OffsetVarNodes_context context;

	context.offset = offset;
	context.sublevels_up = sublevels_up;

	/*
	 * Must be prepared to start with a Query or a bare expression tree; if
	 * it's a Query, go straight to query_tree_walker to make sure that
	 * sublevels_up doesn't get incremented prematurely.
	 */
	if (node && IsA(node, Query))
	{
		Query	   *qry = (Query *) node;

		/*
		 * If we are starting at a Query, and sublevels_up is zero, then we
		 * must also fix rangetable indexes in the Query itself --- namely
		 * resultRelation and rowMarks entries.  sublevels_up cannot be zero
		 * when recursing into a subquery, so there's no need to have the same
		 * logic inside OffsetVarNodes_walker.
		 */
		if (sublevels_up == 0)
		{
			ListCell   *l;

			if (qry->resultRelation)
				qry->resultRelation += offset;
			foreach(l, qry->rowMarks)
				lfirst_int(l) += offset;
		}
		query_tree_walker(qry, OffsetVarNodes_walker,
						  (void *) &context, 0);
	}
	else
		OffsetVarNodes_walker(node, &context);
}

static Relids
offset_relid_set(Relids relids, int offset)
{
	Relids		result = NULL;
	Relids		tmprelids;
	int			rtindex;

	tmprelids = bms_copy(relids);
	while ((rtindex = bms_first_member(tmprelids)) >= 0)
		result = bms_add_member(result, rtindex + offset);
	bms_free(tmprelids);
	return result;
}

/*
 * ChangeVarNodes - adjust Var nodes for a specific change of RT index
 *
 * Find all Var nodes in the given tree belonging to a specific relation
 * (identified by sublevels_up and rt_index), and change their varno fields
 * to 'new_index'.	The varnoold fields are changed too.  Also, adjust other
 * nodes that contain rangetable indexes, such as RangeTblRef and JoinExpr.
 *
 * NOTE: although this has the form of a walker, we cheat and modify the
 * nodes in-place.	The given expression tree should have been copied
 * earlier to ensure that no unwanted side-effects occur!
 */

typedef struct
{
	int			rt_index;
	int			new_index;
	int			sublevels_up;
} ChangeVarNodes_context;

static bool
ChangeVarNodes_walker(Node *node, ChangeVarNodes_context *context)
{
	if (node == NULL)
		return false;
	if (IsA(node, Var))
	{
		Var		   *var = (Var *) node;

		if (var->varlevelsup == context->sublevels_up &&
			var->varno == context->rt_index)
		{
			var->varno = context->new_index;
			var->varnoold = context->new_index;
		}
		return false;
	}
	if (IsA(node, RangeTblRef))
	{
		RangeTblRef *rtr = (RangeTblRef *) node;

		if (context->sublevels_up == 0 &&
			rtr->rtindex == context->rt_index)
			rtr->rtindex = context->new_index;
		/* the subquery itself is visited separately */
		return false;
	}
	if (IsA(node, JoinExpr))
	{
		JoinExpr   *j = (JoinExpr *) node;

		if (context->sublevels_up == 0 &&
			j->rtindex == context->rt_index)
			j->rtindex = context->new_index;
		/* fall through to examine children */
	}
	if (IsA(node, InClauseInfo))
	{
		InClauseInfo *ininfo = (InClauseInfo *) node;

		if (context->sublevels_up == 0)
		{
			ininfo->lefthand = adjust_relid_set(ininfo->lefthand,
												context->rt_index,
												context->new_index);
			ininfo->righthand = adjust_relid_set(ininfo->righthand,
												 context->rt_index,
												 context->new_index);
		}
		/* fall through to examine children */
	}
	if (IsA(node, Query))
	{
		/* Recurse into subselects */
		bool		result;

		context->sublevels_up++;
		result = query_tree_walker((Query *) node, ChangeVarNodes_walker,
								   (void *) context, 0);
		context->sublevels_up--;
		return result;
	}
	return expression_tree_walker(node, ChangeVarNodes_walker,
								  (void *) context);
}

void
ChangeVarNodes(Node *node, int rt_index, int new_index, int sublevels_up)
{
	ChangeVarNodes_context context;

	context.rt_index = rt_index;
	context.new_index = new_index;
	context.sublevels_up = sublevels_up;

	/*
	 * Must be prepared to start with a Query or a bare expression tree; if
	 * it's a Query, go straight to query_tree_walker to make sure that
	 * sublevels_up doesn't get incremented prematurely.
	 */
	if (node && IsA(node, Query))
	{
		Query	   *qry = (Query *) node;

		/*
		 * If we are starting at a Query, and sublevels_up is zero, then we
		 * must also fix rangetable indexes in the Query itself --- namely
		 * resultRelation and rowMarks entries.  sublevels_up cannot be zero
		 * when recursing into a subquery, so there's no need to have the same
		 * logic inside ChangeVarNodes_walker.
		 */
		if (sublevels_up == 0)
		{
			ListCell   *l;

			if (qry->resultRelation == rt_index)
				qry->resultRelation = new_index;
			foreach(l, qry->rowMarks)
			{
				if (lfirst_int(l) == rt_index)
					lfirst_int(l) = new_index;
			}
		}
		query_tree_walker(qry, ChangeVarNodes_walker,
						  (void *) &context, 0);
	}
	else
		ChangeVarNodes_walker(node, &context);
}

/*
 * Substitute newrelid for oldrelid in a Relid set
 */
static Relids
adjust_relid_set(Relids relids, int oldrelid, int newrelid)
{
	if (bms_is_member(oldrelid, relids))
	{
		/* Ensure we have a modifiable copy */
		relids = bms_copy(relids);
		/* Remove old, add new */
		relids = bms_del_member(relids, oldrelid);
		relids = bms_add_member(relids, newrelid);
	}
	return relids;
}

/*
 * IncrementVarSublevelsUp - adjust Var nodes when pushing them down in tree
 *
 * Find all Var nodes in the given tree having varlevelsup >= min_sublevels_up,
 * and add delta_sublevels_up to their varlevelsup value.  This is needed when
 * an expression that's correct for some nesting level is inserted into a
 * subquery.  Ordinarily the initial call has min_sublevels_up == 0 so that
 * all Vars are affected.  The point of min_sublevels_up is that we can
 * increment it when we recurse into a sublink, so that local variables in
 * that sublink are not affected, only outer references to vars that belong
 * to the expression's original query level or parents thereof.
 *
 * Aggref nodes are adjusted similarly.
 *
 * NOTE: although this has the form of a walker, we cheat and modify the
 * Var nodes in-place.	The given expression tree should have been copied
 * earlier to ensure that no unwanted side-effects occur!
 */

typedef struct
{
	int			delta_sublevels_up;
	int			min_sublevels_up;
} IncrementVarSublevelsUp_context;

static bool
IncrementVarSublevelsUp_walker(Node *node,
							   IncrementVarSublevelsUp_context *context)
{
	if (node == NULL)
		return false;
	if (IsA(node, Var))
	{
		Var		   *var = (Var *) node;

		if (var->varlevelsup >= context->min_sublevels_up)
			var->varlevelsup += context->delta_sublevels_up;
		return false;			/* done here */
	}
	if (IsA(node, Aggref))
	{
		Aggref	   *agg = (Aggref *) node;

		if (agg->agglevelsup >= context->min_sublevels_up)
			agg->agglevelsup += context->delta_sublevels_up;
		/* fall through to recurse into argument */
	}
	if (IsA(node, Query))
	{
		/* Recurse into subselects */
		bool		result;

		context->min_sublevels_up++;
		result = query_tree_walker((Query *) node,
								   IncrementVarSublevelsUp_walker,
								   (void *) context, 0);
		context->min_sublevels_up--;
		return result;
	}
	return expression_tree_walker(node, IncrementVarSublevelsUp_walker,
								  (void *) context);
}

void
IncrementVarSublevelsUp(Node *node, int delta_sublevels_up,
						int min_sublevels_up)
{
	IncrementVarSublevelsUp_context context;

	context.delta_sublevels_up = delta_sublevels_up;
	context.min_sublevels_up = min_sublevels_up;

	/*
	 * Must be prepared to start with a Query or a bare expression tree; if
	 * it's a Query, we don't want to increment sublevels_up.
	 */
	query_or_expression_tree_walker(node,
									IncrementVarSublevelsUp_walker,
									(void *) &context,
									0);
}


/*
 * rangeTableEntry_used - detect whether an RTE is referenced somewhere
 *	in var nodes or join or setOp trees of a query or expression.