path: root/src/backend/optimizer/path/allpaths.c

/*-------------------------------------------------------------------------
 *
 * allpaths.c--
 *    Routines to find possible search paths for processing a query
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    $Header: /cvsroot/pgsql/src/backend/optimizer/path/allpaths.c,v 1.1.1.1 1996/07/09 06:21:35 scrappy Exp $
 *
 *-------------------------------------------------------------------------
 */
#include <string.h>

#include "postgres.h"

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

#include "optimizer/internal.h"

#include "optimizer/paths.h"
#include "optimizer/pathnode.h"
#include "optimizer/clauses.h"
#include "optimizer/xfunc.h"
#include "optimizer/cost.h"

#include "commands/creatinh.h"

static void find_rel_paths(Query *root, List *rels);
static List *find_join_paths(Query *root, List *outer_rels, int levels_left);

/*    
 * find-paths--
 *    Finds all possible access paths for executing a query, returning the
 *    top level list of relation entries.  
 *    
 * 'rels' is the list of single relation entries appearing in the query
 */
List *
find_paths(Query *root, List *rels)
{
    int levels_left;

    /*
     * Set the number of join (not nesting) levels yet to be processed.
     */
    levels_left = length(rels);

    if (levels_left <= 0)
	return NIL;

    /*
     * Find the base relation paths.
     */
    find_rel_paths(root, rels);
	
    if (levels_left <= 1) {
	/*
	 * Unsorted single relation, no more processing is required.
	 */
	return (rels);   
    }else {
	/* 
	 * this means that joins or sorts are required.
	 * set selectivities of clauses that have not been set
	 * by an index.
	 */
	set_rest_relselec(root, rels);

	return(find_join_paths(root, rels, levels_left-1));
    }
}

/*    
 * find-rel-paths--
 *    Finds all paths available for scanning each relation entry in 
 *    'rels'.  Sequential scan and any available indices are considered
 *    if possible(indices are not considered for lower nesting levels).
 *    All unique paths are attached to the relation's 'pathlist' field.
 *    
 *    MODIFIES: rels
 */
static void
find_rel_paths(Query *root, List *rels)
{
    List *temp;
    Rel *rel;
    List *lastpath;
     
    foreach(temp, rels) {
	List *sequential_scan_list;
	List *rel_index_scan_list;
	List *or_index_scan_list;

	rel = (Rel *)lfirst(temp);
	sequential_scan_list = lcons(create_seqscan_path(rel),
				    NIL);

	rel_index_scan_list = 
	    find_index_paths(root, 
			     rel,
			     find_relation_indices(root,rel),
			     rel->clauseinfo,
			     rel->joininfo);

	or_index_scan_list = 
	    create_or_index_paths(root, rel, rel->clauseinfo);

	rel->pathlist = add_pathlist(rel,
				     sequential_scan_list,
				     append(rel_index_scan_list, 
					    or_index_scan_list));
    
	/* The unordered path is always the last in the list.  
	 * If it is not the cheapest path, prune it.
	 */
	lastpath = rel->pathlist;
	while(lnext(lastpath)!=NIL)
	    lastpath=lnext(lastpath);
	prune_rel_path(rel, (Path*)lfirst(lastpath));
      /*
       * if there is a qualification of sequential scan the selec.
       * value is not set -- so set it explicitly -- Sunita
       */
      set_rest_selec(root, rel->clauseinfo);
	rel->size = compute_rel_size(rel);
	rel->width = compute_rel_width(rel);
    }
    return;
}

/*    
 * find-join-paths--
 *    Find all possible joinpaths for a query by successively finding ways
 *    to join single relations into join relations.  
 *
 *    if BushyPlanFlag is set, bushy tree plans will be generated:
 *    Find all possible joinpaths(bushy trees) for a query by systematically
 *    finding ways to join relations(both original and derived) together.
 *    
 * 'outer-rels' is the current list of relations for which join paths 
 *   		are to be found, i.e., he current list of relations that 
 *		have already been derived.
 * 'levels-left' is the current join level being processed, where '1' is
 *    		the "last" level
 *    
 * Returns the final level of join relations, i.e., the relation that is
 * the result of joining all the original relations togehter.
 */
static List *
find_join_paths(Query *root, List *outer_rels, int levels_left)
{
    List *x;
    List *new_rels;
    Rel *rel;

    /*
     * Determine all possible pairs of relations to be joined at this level.
     * Determine paths for joining these relation pairs and modify 'new-rels'
     * accordingly, then eliminate redundant join relations.
     */
    new_rels = find_join_rels(root, outer_rels);

    find_all_join_paths(root, new_rels);

    new_rels = prune_joinrels(new_rels);

#if 0    
    /* 
     ** for each expensive predicate in each path in each distinct rel, 
     ** consider doing pullup  -- JMH 
     */
    if (XfuncMode != XFUNC_NOPULL && XfuncMode != XFUNC_OFF)
	foreach(x, new_rels)
	    xfunc_trypullup((Rel*)lfirst(x));
#endif

    prune_rel_paths(new_rels);

    if(BushyPlanFlag) {
	/*
	 * In case of bushy trees
	 * if there is still a join between a join relation and another
	 * relation, add a new joininfo that involves the join relation
	 * to the joininfo list of the other relation
	 */
	add_new_joininfos(root, new_rels,outer_rels);
    }

    foreach(x, new_rels) {
	rel = (Rel*)lfirst(x);
	rel->size = compute_rel_size(rel);
	rel->width = compute_rel_width(rel);

/*#define OPTIMIZER_DEBUG*/
#ifdef OPTIMIZER_DEBUG
	printf("levels left: %d\n", levels_left);
	debug_print_rel(root, rel);
#endif	
    }

    if(BushyPlanFlag) {
	/* 
	 * prune rels that have been completely incorporated into
	 * new join rels
	 */
	outer_rels = prune_oldrels(outer_rels);
	/* 
	 * merge join rels if then contain the same list of base rels
	 */
	outer_rels = merge_joinrels(new_rels,outer_rels);
	root->join_relation_list_ = outer_rels;
    }
    else {
	root->join_relation_list_ = new_rels;
    }

    if(levels_left == 1) {
	if(BushyPlanFlag)
	    return(final_join_rels(outer_rels));
	else
	    return(new_rels);
    } else {
	if(BushyPlanFlag)
	    return(find_join_paths(root, outer_rels, levels_left - 1));
	else
	    return(find_join_paths(root, new_rels, levels_left - 1));
    } 
}

/*****************************************************************************
 *
 *****************************************************************************/

static void
print_joinclauses(Query *root, List *clauses)
{
    List *l;
    extern void print_expr(Node *expr, List *rtable); /* in print.c */

    foreach(l, clauses) {
	CInfo *c = lfirst(l);

	print_expr((Node*)c->clause, root->rtable);
	if (lnext(l)) printf(" ");
    }
}

void
print_path(Query *root, Path *path, int indent)
{
    char *ptype = NULL;
    JoinPath *jp;
    bool join;
    int i;

    for(i=0; i < indent; i++)
	printf("\t");
    
    switch(nodeTag(path)) {
    case T_Path:
	ptype = "SeqScan"; join=false; break;
    case T_IndexPath:
	ptype = "IdxScan"; join=false; break;
    case T_JoinPath:
	ptype = "Nestloop"; join=true; break;
    case T_MergePath:
	ptype = "MergeJoin"; join=true; break;
    case T_HashPath:
	ptype = "HashJoin"; join=true; break;
    default:
	break;
    }
    if (join) {
	int size = path->parent->size;
	jp = (JoinPath*)path;
	printf("%s size=%d cost=%f\n", ptype, size, path->path_cost);
	switch(nodeTag(path)) {
	case T_MergePath:
	case T_HashPath:
	    for(i=0; i < indent+1; i++)
		printf("\t");
	    printf("   clauses=(");
	    print_joinclauses(root,
			      ((JoinPath*)path)->pathclauseinfo);
	    printf(")\n");

	    if (nodeTag(path)==T_MergePath) {
		MergePath *mp = (MergePath*)path;
		if (mp->outersortkeys || mp->innersortkeys) {
		    for(i=0; i < indent+1; i++)
			printf("\t");
		    printf("   sortouter=%d sortinner=%d\n",
			   ((mp->outersortkeys)?1:0),
			   ((mp->innersortkeys)?1:0));
		}
	    }
	    break;
	default:
	    break;
	}
	print_path(root, jp->outerjoinpath, indent+1);
	print_path(root, jp->innerjoinpath, indent+1);
    } else {
	int size = path->parent->size;
	int relid = lfirsti(path->parent->relids);
	printf("%s(%d) size=%d cost=%f",
	       ptype, relid, size, path->path_cost);

	if (nodeTag(path)==T_IndexPath) {
	    List *k, *l;

	    printf(" keys=");
	    foreach (k, path->keys) {
		printf("(");
		foreach (l, lfirst(k)) {
		    Var *var = lfirst(l);
		    printf("%d.%d", var->varnoold, var->varoattno);
		    if (lnext(l)) printf(", ");
		}
		printf(")");
		if (lnext(k)) printf(", ");
	    }
	}
	printf("\n");
    }
}

#ifdef OPTIMIZER_DEBUG
static void 
debug_print_rel(Query *root, Rel *rel)
{
    List *l;

    printf("(");
    foreach(l, rel->relids) {
	printf("%d ", lfirsti(l));
    }
    printf("): size=%d width=%d\n", rel->size, rel->width);

    printf("\tpath list:\n");
    foreach (l, rel->pathlist) {
	print_path(root, lfirst(l), 1);
    }
    printf("\tcheapest path:\n");
    print_path(root, rel->cheapestpath, 1);
}
#endif /* OPTIMIZER_DEBUG */