postgres/src/backend/optimizer/prep/preptlist.c

/*-------------------------------------------------------------------------
 *
 * preptlist.c--
 *    Routines to preprocess the parse tree target list
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    $Header: /cvsroot/pgsql/src/backend/optimizer/prep/preptlist.c,v 1.2 1997/01/22 01:42:38 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#include <string.h>
#include "postgres.h"

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

#include "nodes/makefuncs.h"

#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/palloc.h"

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

#include "optimizer/internal.h"
#include "optimizer/prep.h"
#include "optimizer/clauses.h"
#include "optimizer/tlist.h"

static List *expand_targetlist(List *tlist, Oid relid, int command_type,
			       Index result_relation);
static List *replace_matching_resname(List *new_tlist,
				      List *old_tlist);
static List *new_relation_targetlist(Oid relid, Index rt_index,
				     NodeTag node_type);
					 

/*    
 * preprocess-targetlist--
 *    Driver for preprocessing the parse tree targetlist.
 *    
 *    1. Deal with appends and replaces by filling missing attributes
 *       in the target list.
 *    2. Reset operator OIDs to the appropriate regproc ids.
 *    
 *    Returns the new targetlist.
 */
List *
preprocess_targetlist(List *tlist,
		      int command_type,
		      Index result_relation,
		      List *range_table)
{
    List *expanded_tlist = NIL;
    Oid relid = InvalidOid;
    List *t_list = NIL;
    List *temp = NIL;

    if (result_relation>=1 && command_type != CMD_SELECT) {
	relid = getrelid(result_relation, range_table);
    }
     
    /*
     * for heap_formtuple to work, the targetlist must match the exact
     * order of the attributes. We also need to fill in the missing
     * attributes here. 			-ay 10/94
     */
    expanded_tlist =
	expand_targetlist(tlist, relid, command_type, result_relation);

    /*    XXX should the fix-opids be this early?? */
    /*    was mapCAR  */
    foreach (temp,expanded_tlist) {
	TargetEntry *tle = lfirst(temp);
	if (tle->expr)
	    fix_opid(tle->expr);
    }
    t_list = copyObject(expanded_tlist);

    /* ------------------
     *  for "replace" or "delete" queries, add ctid of the result
     *  relation into the target list so that the ctid can get
     *  propogate through the execution and in the end ExecReplace()
     *  will find the right tuple to replace or delete.  This
     *  extra field will be removed in ExecReplace().
     *  For convinient, we append this extra field to the end of
     *  the target list.
     * ------------------
     */
    if (command_type == CMD_UPDATE || command_type == CMD_DELETE) {
	TargetEntry *ctid;
	Resdom *resdom;
	Var *var;

	resdom = makeResdom(length(t_list) + 1,
			    27,
			    6,
			    "ctid",
			    0,
			    0,
			    1);

	var = makeVar(result_relation, -1, 27, result_relation, -1);

	ctid = makeNode(TargetEntry);
	ctid->resdom = resdom;
	ctid->expr = (Node *)var;
	t_list = lappend(t_list, ctid);
    }

    return(t_list);
}

/*****************************************************************************
 *
 *     	TARGETLIST EXPANSION
 *
 *****************************************************************************/

/*    
 * expand-targetlist--
 *    Given a target list as generated by the parser and a result relation,
 *    add targetlist entries for the attributes which have not been used.
 *    
 *    XXX This code is only supposed to work with unnested relations.
 *    
 *    'tlist' is the original target list
 *    'relid' is the relid of the result relation
 *    'command' is the update command
 *    
 * Returns the expanded target list, sorted in resno order.
 */
static List *
expand_targetlist(List *tlist,
		  Oid relid,
		  int command_type,
		  Index result_relation)
{
    NodeTag node_type = T_Invalid;
    
    switch (command_type) {
    case CMD_INSERT:
	node_type = (NodeTag)T_Const;
	break;
    case CMD_UPDATE:
	node_type = (NodeTag)T_Var;
	break;
    } 
    
    if(node_type != T_Invalid) {
	List *ntlist = new_relation_targetlist(relid,
					       result_relation,
					       node_type);

	return (replace_matching_resname(ntlist, tlist));
    } else {
	return (tlist);
    }
    
}


static List *
replace_matching_resname(List *new_tlist, List *old_tlist)
{
    List *temp, *i;
    List *t_list = NIL;
     
    foreach (i,new_tlist) {
	TargetEntry *new_tle = (TargetEntry *)lfirst(i);
	TargetEntry *matching_old_tl = NULL;

	foreach (temp, old_tlist) {
	    TargetEntry *old_tle = (TargetEntry *)lfirst(temp);
	    
	    old_tle = lfirst(temp);
	    if (!strcmp(old_tle->resdom->resname,
			new_tle->resdom->resname)) {
		matching_old_tl = old_tle;
		break;
	    }
	}
	  
	if(matching_old_tl) {
	    matching_old_tl->resdom->resno =
		new_tle->resdom->resno;
	    t_list = lappend(t_list, matching_old_tl);
	} 
	else {
	    t_list = lappend(t_list, new_tle);
	} 
    }

    /*
     * It is possible that 'old_tlist' has some negative
     * attributes (i.e. negative resnos). This only happens
     * if this is a replace/append command and we explicitly
     * specify a system attribute. Of course this is not a very good
     * idea if this is a user query, but on the other hand the rule
     * manager uses this mechanism to replace rule locks.
     *
     * So, copy all these entries to the end of the target list
     * and set their 'resjunk' value to 1 to show that these are
     * special attributes and have to be treated specially by the
     * executor!
     */
    foreach (temp, old_tlist) {
	TargetEntry *old_tle, *new_tl;
	Resdom *newresno;

	old_tle = lfirst(temp);
	if (old_tle->resdom->resno < 0) {
	    newresno = (Resdom*) copyObject((Node*)old_tle->resdom);
	    newresno->resno = length(t_list) +1;
	    newresno->resjunk = 1;
	    new_tl = MakeTLE(newresno, old_tle->expr);
	    t_list = lappend(t_list, new_tl);
	}
    }

    return (t_list);
}

/*    
 * new-relation-targetlist--
 *    Generate a targetlist for the relation with relation OID 'relid'
 *    and rangetable index 'rt-index'.
 *    
 *    Returns the new targetlist.
 */
static List *
new_relation_targetlist(Oid relid, Index rt_index, NodeTag node_type)
{
    AttrNumber attno;
    List *t_list = NIL;
    char *attname;
    Oid atttype = 0;
    int16 typlen = 0;
    bool attisset = false;
/*    Oid type_id; */
/*    type_id = RelationIdGetTypeId(relid); */

    for(attno=1; attno <= get_relnatts(relid); attno++) {
	attname = get_attname(/*type_id,*/ relid, attno);
	atttype = get_atttype(/*type_id,*/ relid, attno);
	/*
	 * Since this is an append or replace, the size of any set
	 * attribute is the size of the OID used to represent it.
	 */
	attisset = get_attisset(/* type_id,*/ relid, attname);
	if (attisset) {
	    typlen = tlen(type("oid"));
	} else {
	    typlen = get_typlen(atttype);
	}
	
	switch (node_type) {
	case T_Const:
	    { 
		struct varlena *typedefault = get_typdefault(atttype);
		int temp = 0;
		Const *temp2 = (Const*)NULL;
		TargetEntry *temp3 = (TargetEntry *)NULL;

		if (typedefault==NULL) 
		    temp = 0;
		else 
		    temp = typlen;
		 
		temp2 = makeConst (atttype,
				   temp,
				   (Datum)typedefault,
				   (typedefault == (struct varlena *)NULL),
				   /* XXX this is bullshit */
				   false,
				   false, /* not a set */
				   false);
		 
		temp3 = MakeTLE (makeResdom(attno,
					    atttype,
					    typlen,
					    attname,
					    0,
					    (Oid)0,
					    0),
				 (Node*)temp2);
		t_list = lappend(t_list,temp3);
		break;
	    } 
	case T_Var:
	    { 
		Var *temp_var = (Var*)NULL;
		TargetEntry *temp_list = NULL;

		temp_var =
		    makeVar(rt_index, attno, atttype, rt_index, attno);

		temp_list = MakeTLE(makeResdom(attno,
					       atttype,
					       typlen,
					       attname,
					       0,
					       (Oid)0,
					       0),
				    (Node*)temp_var);
		t_list = lappend(t_list,temp_list);
		break;
	    }
	default: 		/* do nothing */
	    break;
	}
    }

    return(t_list);
}