mergeutils.c 3.23 KB
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/*-------------------------------------------------------------------------
 *
 * mergeutils.c--
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 *	  Utilities for finding applicable merge clauses and pathkeys
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 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
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 *	  $Header: /cvsroot/pgsql/src/backend/optimizer/path/Attic/mergeutils.c,v 1.16 1999/02/10 03:52:41 momjian Exp $
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 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "nodes/pg_list.h"
#include "nodes/relation.h"

#include "optimizer/internal.h"
#include "optimizer/paths.h"
#include "optimizer/clauses.h"
#include "optimizer/ordering.h"

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/*
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 * group-clauses-by-order--
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 *	  If a join clause node in 'restrictinfo-list' is mergejoinable, store
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 *	  it within a mergeinfo node containing other clause nodes with the same
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 *	  mergejoin ordering.
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 *
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 * 'restrictinfo-list' is the list of restrictinfo nodes
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 * 'inner-relid' is the relid of the inner join relation
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 *
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 * Returns the new list of mergeinfo nodes.
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 *
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 */
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List *
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group_clauses_by_order(List *restrictinfo_list,
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					   int inner_relid)
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{
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	List	   *mergeinfo_list = NIL;
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	List	   *xrestrictinfo = NIL;
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	foreach(xrestrictinfo, restrictinfo_list)
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	{
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		RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(xrestrictinfo);
		MergeOrder *merge_ordering = restrictinfo->mergejoinorder;
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		if (merge_ordering)
		{

			/*
			 * Create a new mergeinfo node and add it to 'mergeinfo-list'
			 * if one does not yet exist for this merge ordering.
			 */
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			PathOrder	*path_order;
			MergeInfo	*xmergeinfo;
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			Expr	   *clause = restrictinfo->clause;
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			Var		   *leftop = get_leftop(clause);
			Var		   *rightop = get_rightop(clause);
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			JoinKey    *jmkeys;
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			path_order = makeNode(PathOrder);
			path_order->ordtype = MERGE_ORDER;
			path_order->ord.merge = merge_ordering;
			xmergeinfo = match_order_mergeinfo(path_order, mergeinfo_list);
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			if (inner_relid == leftop->varno)
			{
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				jmkeys = makeNode(JoinKey);
				jmkeys->outer = rightop;
				jmkeys->inner = leftop;
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			}
			else
			{
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				jmkeys = makeNode(JoinKey);
				jmkeys->outer = leftop;
				jmkeys->inner = rightop;
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			}

			if (xmergeinfo == NULL)
			{
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				xmergeinfo = makeNode(MergeInfo);
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				xmergeinfo->m_ordering = merge_ordering;
				mergeinfo_list = lcons(xmergeinfo,
									   mergeinfo_list);
			}

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			((JoinMethod *) xmergeinfo)->clauses = lcons(clause,
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					  ((JoinMethod *) xmergeinfo)->clauses);
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			((JoinMethod *) xmergeinfo)->jmkeys = lcons(jmkeys,
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					  ((JoinMethod *) xmergeinfo)->jmkeys);
		}
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	}
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	return mergeinfo_list;
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}


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/*
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 * match-order-mergeinfo--
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 *	  Searches the list 'mergeinfo-list' for a mergeinfo node whose order
 *	  field equals 'ordering'.
 *
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 * Returns the node if it exists.
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 *
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 */
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MergeInfo *
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match_order_mergeinfo(PathOrder *ordering, List *mergeinfo_list)
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{
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	MergeOrder *xmergeorder;
	List	   *xmergeinfo = NIL;
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	foreach(xmergeinfo, mergeinfo_list)
	{
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		MergeInfo	   *mergeinfo = (MergeInfo *) lfirst(xmergeinfo);
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		xmergeorder = mergeinfo->m_ordering;
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		if ((ordering->ordtype == MERGE_ORDER &&
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		 equal_merge_ordering(ordering->ord.merge, xmergeorder)) ||
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			(ordering->ordtype == SORTOP_ORDER &&
		   equal_path_merge_ordering(ordering->ord.sortop, xmergeorder)))
		{
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			return mergeinfo;
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		}
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	}
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	return (MergeInfo *) NIL;
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}