postgresql/src/backend/optimizer/util/pathnode.c

/*-------------------------------------------------------------------------
 *
 * pathnode.c--
 *    Routines to manipulate pathlists and create path nodes
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    $Header: /cvsroot/pgsql/src/backend/optimizer/util/pathnode.c,v 1.3 1997/09/05 18:10:36 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#include <math.h>

#include "postgres.h"

#include "nodes/relation.h"
#include "utils/elog.h"

#include "optimizer/internal.h"
#include "optimizer/pathnode.h"
#include "optimizer/clauseinfo.h"
#include "optimizer/plancat.h"
#include "optimizer/cost.h"
#include "optimizer/keys.h"
#include "optimizer/xfunc.h"
#include "optimizer/ordering.h"

#include "parser/parsetree.h"		/* for getrelid() */

static Path *better_path(Path *new_path, List *unique_paths, bool *noOther);


/*****************************************************************************
 *    	MISC. PATH UTILITIES
 *****************************************************************************/

/*    
 * path-is-cheaper--
 *    Returns t iff 'path1' is cheaper than 'path2'.
 *    
 */
bool
path_is_cheaper(Path *path1, Path *path2)
{
    Cost cost1 = path1->path_cost;
    Cost cost2 = path2->path_cost;

    return((bool)(cost1 < cost2));
}

/*    
 * set_cheapest--
 *    Finds the minimum cost path from among a relation's paths.  
 *    
 * 'parent-rel' is the parent relation
 * 'pathlist' is a list of path nodes corresponding to 'parent-rel'
 *    
 * Returns and sets the relation entry field with the pathnode that 
 * is minimum.
 *    
 */
Path *
set_cheapest(Rel *parent_rel, List *pathlist)
{
    List *p;
    Path *cheapest_so_far;

    Assert(pathlist!=NIL);
    Assert(IsA(parent_rel,Rel));

    cheapest_so_far = (Path*)lfirst(pathlist);

    foreach (p, lnext(pathlist)) {
	Path *path = (Path*)lfirst(p);

	if (path_is_cheaper(path, cheapest_so_far)) {
	    cheapest_so_far = path;
	}
    }

    parent_rel->cheapestpath = cheapest_so_far;

    return(cheapest_so_far);
}

/*    
 * add_pathlist--
 *    For each path in the list 'new-paths', add to the list 'unique-paths' 
 *    only those paths that are unique (i.e., unique ordering and ordering 
 *    keys).  Should a conflict arise, the more expensive path is thrown out,
 *    thereby pruning the plan space.  But we don't prune if xfunc
 *    told us not to.
 *    
 * 'parent-rel' is the relation entry to which these paths correspond.
 *    
 * Returns the list of unique pathnodes.
 *    
 */
List *
add_pathlist(Rel *parent_rel, List *unique_paths, List *new_paths)
{
    List *x;
    Path *new_path;
    Path *old_path;
    bool noOther;

    foreach (x, new_paths) {
	new_path = (Path*)lfirst(x);
	if (member(new_path, unique_paths)) 
	    continue;
	old_path = better_path(new_path,unique_paths,&noOther);

	if (noOther) {
	    /*  Is a brand new path.  */
	    new_path->parent = parent_rel;
	    unique_paths = lcons(new_path, unique_paths);
	} else if (old_path==NULL) {
	    ;	/* do nothing if path is not cheaper */
	} else if (old_path != NULL) { /* (IsA(old_path,Path)) { */
	    new_path->parent = parent_rel;
	    if (!parent_rel->pruneable) {
		unique_paths = lcons(new_path, unique_paths);
	    }else
		unique_paths = lcons(new_path,
				    LispRemove(old_path,unique_paths));
	}
    }
    return(unique_paths);
}

/*    
 * better_path--
 *    Determines whether 'new-path' has the same ordering and keys as some 
 *    path in the list 'unique-paths'.  If there is a redundant path,
 *    eliminate the more expensive path.
 *    
 * Returns:
 *    The old path - if 'new-path' matches some path in 'unique-paths' and is
 *    		cheaper
 *    nil - if 'new-path' matches but isn't cheaper
 *    t - if there is no path in the list with the same ordering and keys
 *    
 */
static Path *
better_path(Path *new_path, List *unique_paths, bool *noOther)
{
    Path *old_path = (Path*)NULL;
    Path *path = (Path*)NULL;
    List *temp = NIL;
    Path *retval = NULL;

    /* XXX - added the following two lines which weren't int
     * the lisp planner, but otherwise, doesn't seem to work
     * for the case where new_path is 'nil
     */
    foreach (temp,unique_paths) {
	path = (Path*) lfirst(temp);

	if ((equal_path_path_ordering(&new_path->p_ordering,
				      &path->p_ordering) &&
	     samekeys(new_path->keys, path->keys))) {
	    old_path = path;
	    break;
	}
    }

    if (old_path==NULL) {
	*noOther = true;
    } else { 
	*noOther = false;
	if (path_is_cheaper(new_path,old_path)) {
	    retval = old_path;
	}
    }
     
    return(retval);
}



/*****************************************************************************
 *    	PATH NODE CREATION ROUTINES
 *****************************************************************************/

/*    
 * create_seqscan_path--
 *    Creates a path corresponding to a sequential scan, returning the
 *    pathnode.
 *    
 */
Path *
create_seqscan_path(Rel *rel)
{
    int relid=0;

    Path *pathnode = makeNode(Path);

    pathnode->pathtype = T_SeqScan; 
    pathnode->parent = rel;
    pathnode->path_cost = 0.0;
    pathnode->p_ordering.ordtype = SORTOP_ORDER;
    pathnode->p_ordering.ord.sortop = NULL;
    pathnode->keys = NIL;
    /* copy clauseinfo list into path for expensive function processing 
     * -- JMH, 7/7/92
     */
    pathnode->locclauseinfo= 
	(List*)copyObject((Node*)rel->clauseinfo);

    if (rel->relids !=NULL)
	relid = lfirsti(rel->relids);

    pathnode->path_cost = cost_seqscan (relid,
					rel->pages, rel->tuples);
    /* add in expensive functions cost!  -- JMH, 7/7/92 */
#if 0
    if (XfuncMode != XFUNC_OFF) {
	pathnode->path_cost +=
	    xfunc_get_path_cost(pathnode);
    }
#endif
    return (pathnode);
}

/*    
 * create_index_path--
 *    Creates a single path node for an index scan.
 *    
 * 'rel' is the parent rel
 * 'index' is the pathnode for the index on 'rel'
 * 'restriction-clauses' is a list of restriction clause nodes.
 * 'is-join-scan' is a flag indicating whether or not the index is being
 * 	considered because of its sort order.
 *    
 * Returns the new path node.
 *    
 */
IndexPath *
create_index_path(Query *root,
                  Rel *rel,
		  Rel *index,
		  List *restriction_clauses,
		  bool is_join_scan)
{
    IndexPath *pathnode = makeNode(IndexPath);
    
    pathnode->path.pathtype = T_IndexScan;
    pathnode->path.parent = rel;
    pathnode->path.p_ordering.ordtype = SORTOP_ORDER;
    pathnode->path.p_ordering.ord.sortop = index->ordering;

    pathnode->indexid = index->relids;
    pathnode->indexkeys = index->indexkeys;
    pathnode->indexqual = NIL;

    /* copy clauseinfo list into path for expensive function processing 
     *  -- JMH, 7/7/92
     */
    pathnode->path.locclauseinfo =
	set_difference((List*) copyObject((Node*)rel->clauseinfo),
		       (List*) restriction_clauses);

    /*
     * The index must have an ordering for the path to have (ordering) keys, 
     * and vice versa.
     */
    if (pathnode->path.p_ordering.ord.sortop) {
	pathnode->path.keys = collect_index_pathkeys(index->indexkeys,
						     rel->targetlist);
	/*
	 * Check that the keys haven't 'disappeared', since they may 
	 * no longer be in the target list (i.e., index keys that are not 
	 * relevant to the scan are not applied to the scan path node,
	 * so if no index keys were found, we can't order the path).
	 */
	if (pathnode->path.keys==NULL) {
	    pathnode->path.p_ordering.ord.sortop = NULL;
	}
    } else {
	pathnode->path.keys = NULL;
    }

    if (is_join_scan || restriction_clauses==NULL) {
	/*
	 * Indices used for joins or sorting result nodes don't
	 * restrict the result at all, they simply order it,
	 * so compute the scan cost 
	 * accordingly -- use a selectivity of 1.0.
	 */
/* is the statement above really true?  what about IndexScan as the 
   inner of a join? */
	pathnode->path.path_cost =
	    cost_index (lfirsti(index->relids),
			index->pages,
			1.0,
			rel->pages,
			rel->tuples,
			index->pages,
			index->tuples,
			false);
	/* add in expensive functions cost!  -- JMH, 7/7/92 */
#if 0
	if (XfuncMode != XFUNC_OFF) {
	    pathnode->path_cost =
		(pathnode->path_cost +
		 xfunc_get_path_cost((Path*)pathnode));
	}
#endif
    } else  {
	/*
	 * Compute scan cost for the case when 'index' is used with a 
	 * restriction clause.
	 */
	List *attnos;
	List *values;
	List *flags;
	float npages;
	float selec;
	Cost clausesel;

	get_relattvals(restriction_clauses,
		       &attnos,
		       &values,
		       &flags);
	index_selectivity(lfirsti(index->relids),
			  index->classlist,
			  get_opnos(restriction_clauses),
			  getrelid(lfirsti(rel->relids),
				   root->rtable),
			  attnos,
			  values,
			  flags,
			  length(restriction_clauses),
			  &npages,
			  &selec);
	/*   each clause gets an equal selectivity */
	clausesel = 
	    pow(selec, 
		1.0 / (double) length(restriction_clauses));
    
	pathnode->indexqual = restriction_clauses;
	pathnode->path.path_cost =
	    cost_index (lfirsti(index->relids),
			(int)npages,
			selec,
			rel->pages,
			rel->tuples,
			index->pages,
			index->tuples,
			false);

#if 0
	/* add in expensive functions cost!  -- JMH, 7/7/92 */
	if (XfuncMode != XFUNC_OFF) {
	    pathnode->path_cost += 
		xfunc_get_path_cost((Path*)pathnode);
	}
#endif
	/* Set selectivities of clauses used with index to the selectivity 
	 * of this index, subdividing the selectivity equally over each of 
	 * the clauses. 
	 */

	/* XXX Can this divide the selectivities in a better way? */
	set_clause_selectivities(restriction_clauses, clausesel);
    }
    return(pathnode);
}

/*    
 * create_nestloop_path--
 *    Creates a pathnode corresponding to a nestloop join between two 
 *    relations.
 *    
 * 'joinrel' is the join relation.
 * 'outer_rel' is the outer join relation
 * 'outer_path' is the outer join path.
 * 'inner_path' is the inner join path.
 * 'keys' are the keys of the path
 *    	
 * Returns the resulting path node.
 *    
 */
JoinPath *
create_nestloop_path(Rel *joinrel,
		     Rel *outer_rel,
		     Path *outer_path,
		     Path *inner_path,
		     List *keys)
{
    JoinPath *pathnode = makeNode(JoinPath);
     
    pathnode->path.pathtype = T_NestLoop;
    pathnode->path.parent  = joinrel;
    pathnode->outerjoinpath = outer_path;
    pathnode->innerjoinpath = inner_path;
    pathnode->pathclauseinfo = joinrel->clauseinfo;
    pathnode->path.keys = keys;
    pathnode->path.joinid = NIL;
    pathnode->path.outerjoincost = (Cost)0.0;
    pathnode->path.locclauseinfo = NIL;

    if (keys) {
	pathnode->path.p_ordering.ordtype =
	    outer_path->p_ordering.ordtype;
	if (outer_path->p_ordering.ordtype == SORTOP_ORDER) {
	    pathnode->path.p_ordering.ord.sortop =
		outer_path->p_ordering.ord.sortop;
	} else {
	    pathnode->path.p_ordering.ord.merge =
		outer_path->p_ordering.ord.merge;
	}
    } else {
	pathnode->path.p_ordering.ordtype = SORTOP_ORDER;
	pathnode->path.p_ordering.ord.sortop = NULL;
    }

    pathnode->path.path_cost  = 
	cost_nestloop(outer_path->path_cost,
		      inner_path->path_cost,
		      outer_rel->size,
		      inner_path->parent->size,
		      page_size(outer_rel->size,
				outer_rel->width),
		      IsA(inner_path,IndexPath));
    /* add in expensive function costs -- JMH 7/7/92 */
#if 0
    if (XfuncMode != XFUNC_OFF) {
	pathnode->path_cost += xfunc_get_path_cost((Path*)pathnode);
    }
#endif
    return(pathnode);
}

/*    
 * create_mergesort_path--
 *    Creates a pathnode corresponding to a mergesort join between
 *    two relations
 *    
 * 'joinrel' is the join relation
 * 'outersize' is the number of tuples in the outer relation
 * 'innersize' is the number of tuples in the inner relation
 * 'outerwidth' is the number of bytes per tuple in the outer relation
 * 'innerwidth' is the number of bytes per tuple in the inner relation
 * 'outer_path' is the outer path
 * 'inner_path' is the inner path
 * 'keys' are the new keys of the join relation
 * 'order' is the sort order required for the merge
 * 'mergeclauses' are the applicable join/restriction clauses
 * 'outersortkeys' are the sort varkeys for the outer relation
 * 'innersortkeys' are the sort varkeys for the inner relation
 *    
 */
MergePath *
create_mergesort_path(Rel *joinrel,
		      int outersize,
		      int innersize,
		      int outerwidth,
		      int innerwidth,
		      Path *outer_path,
		      Path *inner_path,
		      List *keys,
		      MergeOrder *order,
		      List *mergeclauses,
		      List *outersortkeys,
		      List *innersortkeys)
{
    MergePath *pathnode = makeNode(MergePath);

    pathnode->jpath.path.pathtype  = T_MergeJoin;
    pathnode->jpath.path.parent  = joinrel;
    pathnode->jpath.outerjoinpath = outer_path;
    pathnode->jpath.innerjoinpath = inner_path;
    pathnode->jpath.pathclauseinfo = joinrel->clauseinfo;
    pathnode->jpath.path.keys = keys;
    pathnode->jpath.path.p_ordering.ordtype = MERGE_ORDER;
    pathnode->jpath.path.p_ordering.ord.merge  = order;
    pathnode->path_mergeclauses = mergeclauses;
    pathnode->jpath.path.locclauseinfo = NIL;
    pathnode->outersortkeys = outersortkeys;
    pathnode->innersortkeys = innersortkeys;
    pathnode->jpath.path.path_cost  =
	cost_mergesort(outer_path->path_cost,
		       inner_path->path_cost,
		       outersortkeys,
		       innersortkeys,
		       outersize,
		       innersize,
		       outerwidth,
		       innerwidth);
    /* add in expensive function costs -- JMH 7/7/92 */
#if 0
    if (XfuncMode != XFUNC_OFF) {
	pathnode->path_cost +=
	    xfunc_get_path_cost((Path*)pathnode);
    }
#endif
    return(pathnode);
}

/*    
 * create_hashjoin_path--		 	XXX HASH
 *    Creates a pathnode corresponding to a hash join between two relations.
 *    
 * 'joinrel' is the join relation
 * 'outersize' is the number of tuples in the outer relation
 * 'innersize' is the number of tuples in the inner relation
 * 'outerwidth' is the number of bytes per tuple in the outer relation
 * 'innerwidth' is the number of bytes per tuple in the inner relation
 * 'outer_path' is the outer path
 * 'inner_path' is the inner path
 * 'keys' are the new keys of the join relation
 * 'operator' is the hashjoin operator
 * 'hashclauses' are the applicable join/restriction clauses
 * 'outerkeys' are the sort varkeys for the outer relation
 * 'innerkeys' are the sort varkeys for the inner relation
 *    
 */
HashPath *
create_hashjoin_path(Rel *joinrel,
		     int outersize,
		     int innersize,
		     int outerwidth,
		     int innerwidth,
		     Path *outer_path,
		     Path *inner_path,
		     List *keys,
		     Oid operator,
		     List *hashclauses,
		     List *outerkeys,
		     List *innerkeys)
{
    HashPath *pathnode = makeNode(HashPath);

    pathnode->jpath.path.pathtype  = T_HashJoin; 
    pathnode->jpath.path.parent  = joinrel;
    pathnode->jpath.outerjoinpath = outer_path;
    pathnode->jpath.innerjoinpath = inner_path;
    pathnode->jpath.pathclauseinfo = joinrel->clauseinfo;
    pathnode->jpath.path.locclauseinfo = NIL;
    pathnode->jpath.path.keys = keys;
    pathnode->jpath.path.p_ordering.ordtype = SORTOP_ORDER;
    pathnode->jpath.path.p_ordering.ord.sortop = NULL;
    pathnode->jpath.path.outerjoincost = (Cost)0.0;
    pathnode->jpath.path.joinid =  (Relid)NULL;
    /*    pathnode->hashjoinoperator = operator;  */ 
    pathnode->path_hashclauses = hashclauses;
    pathnode->outerhashkeys = outerkeys;
    pathnode->innerhashkeys = innerkeys;
    pathnode->jpath.path.path_cost  =
	cost_hashjoin(outer_path->path_cost,
		      inner_path->path_cost,
		      outerkeys,
		      innerkeys,
		      outersize,innersize,
		      outerwidth,innerwidth);
    /* add in expensive function costs -- JMH 7/7/92 */
#if 0
    if (XfuncMode != XFUNC_OFF) {
	pathnode->path_cost += 
	    xfunc_get_path_cost((Path*)pathnode);
    }
#endif
    return(pathnode);
}