execJunk.c

/*-------------------------------------------------------------------------
 *
 * junk.c--
 *    Junk attribute support stuff....
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    $Header: /cvsroot/pgsql/src/backend/executor/execJunk.c,v 1.3 1996/11/08 05:55:55 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "utils/palloc.h"
#include "access/heaptuple.h"
#include "access/heapam.h"
#include "executor/executor.h"
#include "nodes/relation.h"
#include "optimizer/tlist.h" /* for MakeTLE */

/*-------------------------------------------------------------------------
 * 	XXX this stuff should be rewritten to take advantage
 * 	    of ExecProject() and the ProjectionInfo node.
 * 	    -cim 6/3/91
 * 
 * An attribute of a tuple living inside the executor, can be
 * either a normal attribute or a "junk" attribute. "junk" attributes
 * never make it out of the executor, i.e. they are never printed,
 * returned or stored in disk. Their only purpose in life is to
 * store some information useful only to the executor, mainly the values
 * of some system attributes like "ctid" or rule locks.
 * 
 * The general idea is the following: A target list consists of a list of
 * Resdom nodes & expression pairs. Each Resdom node has an attribute
 * called 'resjunk'. If the value of this attribute is 1 then the
 * corresponding attribute is a "junk" attribute.
 * 
 * When we initialize a plan  we call 'ExecInitJunkFilter' to create
 * and store the appropriate information in the 'es_junkFilter' attribute of
 * EState.
 * 
 * We then execute the plan ignoring the "resjunk" attributes.
 * 
 * Finally, when at the top level we get back a tuple, we can call
 * 'ExecGetJunkAttribute' to retrieve the value of the junk attributes we
 * are interested in, and 'ExecRemoveJunk' to remove all the junk attributes
 * from a tuple. This new "clean" tuple is then printed, replaced, deleted
 * or inserted.
 * 
 *-------------------------------------------------------------------------
 */

/*-------------------------------------------------------------------------
 * ExecInitJunkFilter
 *
 * Initialize the Junk filter.
 *-------------------------------------------------------------------------
 */
JunkFilter *
ExecInitJunkFilter(List *targetList)
{
    JunkFilter 		*junkfilter;
    List 		*cleanTargetList;
    int 		len, cleanLength;
    TupleDesc 		tupType, cleanTupType;
    List 		*t;
    TargetEntry		*tle;
    Resdom 		*resdom, *cleanResdom;
    int 		resjunk;
    AttrNumber 		cleanResno;
    AttrNumber 		*cleanMap;
    Size 		size;
    Node		*expr; 

    /* ---------------------
     * First find the "clean" target list, i.e. all the entries
     * in the original target list which have a zero 'resjunk'
     * NOTE: make copy of the Resdom nodes, because we have
     * to change the 'resno's...
     * ---------------------
     */
    cleanTargetList = NIL;
    cleanResno = 1;
    
    foreach (t, targetList) {
	TargetEntry *rtarget = lfirst(t);
	if (rtarget->resdom != NULL) {
	    resdom = rtarget->resdom;
	    expr = rtarget->expr;
	    resjunk = resdom->resjunk;
	    if (resjunk == 0) {
		/*
		 * make a copy of the resdom node, changing its resno.
		 */
		cleanResdom = (Resdom *) copyObject(resdom);
		cleanResdom->resno = cleanResno;
		cleanResno ++;
		/*
		 * create a new target list entry
		 */
		tle = makeNode(TargetEntry);
		tle->resdom = cleanResdom;
		tle->expr = expr;
		cleanTargetList = lappend(cleanTargetList, tle);
	    }
	}
	else {
#ifdef SETS_FIXED
	    List *fjListP;
	    Fjoin *cleanFjoin;
	    List *cleanFjList;
	    List *fjList = lfirst(t);
	    Fjoin *fjNode = (Fjoin *)tl_node(fjList);
	    
	    cleanFjoin = (Fjoin)copyObject((Node) fjNode);
	    cleanFjList = lcons(cleanFjoin, NIL);
	    
	    resdom = (Resdom) lfirst(get_fj_innerNode(fjNode));
	    expr =   lsecond(get_fj_innerNode(fjNode));
	    cleanResdom = (Resdom) copyObject((Node) resdom);
	    set_resno(cleanResdom, cleanResno);
	    cleanResno++;
	    tle = (List) MakeTLE(cleanResdom, (Expr) expr);
	    set_fj_innerNode(cleanFjoin, tle);
	    
	    foreach(fjListP, lnext(fjList)) {
		TargetEntry *tle = lfirst(fjListP);

	    	resdom = tle->resdom;
	    	expr = tle->expr;
	    	cleanResdom = (Resdom*) copyObject((Node) resdom);
		cleanResno++;
	    	cleanResdom->Resno = cleanResno;
	    	/*
	     	 * create a new target list entry
	     	 */
	    	tle = (List) MakeTLE(cleanResdom, (Expr) expr);
	    	cleanFjList = lappend(cleanFjList, tle);
	    }
	    lappend(cleanTargetList, cleanFjList);
#endif
	}
    }
    
    /* ---------------------
     * Now calculate the tuple types for the original and the clean tuple
     *
     * XXX ExecTypeFromTL should be used sparingly.  Don't we already
     *	   have the tupType corresponding to the targetlist we are passed?
     *     -cim 5/31/91
     * ---------------------
     */
    tupType = 	   (TupleDesc) ExecTypeFromTL(targetList);
    cleanTupType = (TupleDesc) ExecTypeFromTL(cleanTargetList);
    
    len = 	  ExecTargetListLength(targetList);
    cleanLength = ExecTargetListLength(cleanTargetList);
    
    /* ---------------------
     * Now calculate the "map" between the original tuples attributes
     * and the "clean" tuple's attributes.
     *
     * The "map" is an array of "cleanLength" attribute numbers, i.e.
     * one entry for every attribute of the "clean" tuple.
     * The value of this entry is the attribute number of the corresponding
     * attribute of the "original" tuple.
     * ---------------------
     */
    if (cleanLength > 0) {
	size = cleanLength * sizeof(AttrNumber);
	cleanMap = (AttrNumber*) palloc(size);
	cleanResno = 1;
	foreach (t, targetList) {
	    TargetEntry *tle = lfirst(t);
	    if (tle->resdom != NULL) {
		resdom = tle->resdom;
		expr = tle->expr;
		resjunk = resdom->resjunk;
		if (resjunk == 0) {
		    cleanMap[cleanResno-1] = resdom->resno;
		    cleanResno ++;
		}
	    } else {
#ifdef SETS_FIXED
		List fjListP;
		List fjList = lfirst(t);
		Fjoin fjNode = (Fjoin)lfirst(fjList);

		/* what the hell is this????? */
		resdom = (Resdom) lfirst(get_fj_innerNode(fjNode));
#endif

		cleanMap[cleanResno-1] = tle->resdom->resno;
		cleanResno++;

#ifdef SETS_FIXED
		foreach(fjListP, lnext(fjList)) {
		    TargetEntry *tle = lfirst(fjListP);

		    resdom = tle->resdom;
		    cleanMap[cleanResno-1] = resdom->resno;
		    cleanResno++;
		}
#endif
	    }
	}
    } else {
	cleanMap = NULL;
    }
    
    /* ---------------------
     * Finally create and initialize the JunkFilter.
     * ---------------------
     */
    junkfilter = makeNode(JunkFilter);
    
    junkfilter->jf_targetList = targetList;
    junkfilter->jf_length = len;
    junkfilter->jf_tupType = tupType;
    junkfilter->jf_cleanTargetList = cleanTargetList;
    junkfilter->jf_cleanLength = cleanLength;
    junkfilter->jf_cleanTupType = cleanTupType;
    junkfilter->jf_cleanMap = cleanMap;
    
    return(junkfilter);
    
}

/*-------------------------------------------------------------------------
 * ExecGetJunkAttribute
 *
 * Given a tuple (slot), the junk filter and a junk attribute's name,
 * extract & return the value of this attribute.
 *
 * It returns false iff no junk attribute with such name was found.
 *
 * NOTE: isNull might be NULL !
 *-------------------------------------------------------------------------
 */
bool
ExecGetJunkAttribute(JunkFilter *junkfilter,
		     TupleTableSlot *slot,
		     char *attrName,
		     Datum *value,
		     bool *isNull)
{
    List 		*targetList;
    List 		*t;
    Resdom 		*resdom;
    AttrNumber 		resno;
    char                *resname;
    int 		resjunk;
    TupleDesc 		tupType;
    HeapTuple 		tuple;
    
    /* ---------------------
     * first look in the junkfilter's target list for
     * an attribute with the given name
     * ---------------------
     */
    resno = 	 InvalidAttrNumber;
    targetList = junkfilter->jf_targetList;
    
    foreach (t, targetList) {
	TargetEntry *tle = lfirst(t);
	resdom = tle->resdom;
	resname = resdom->resname;
	resjunk = resdom->resjunk;
	if (resjunk != 0 && (strcmp(resname, attrName) == 0)) {
	    /* We found it ! */
	    resno = resdom->resno;
	    break;
	}
    }
    
    if (resno == InvalidAttrNumber) {
	/* Ooops! We couldn't find this attribute... */
	return(false);
    }
    
    /* ---------------------
     * Now extract the attribute value from the tuple.
     * ---------------------
     */
    tuple = 	slot->val;
    tupType = 	(TupleDesc) junkfilter->jf_tupType;
    
    *value = 	(Datum)
	heap_getattr(tuple, InvalidBuffer, resno, tupType, isNull);
    
    return true;
}

/*-------------------------------------------------------------------------
 * ExecRemoveJunk
 *
 * Construct and return a tuple with all the junk attributes removed.
 *-------------------------------------------------------------------------
 */
HeapTuple
ExecRemoveJunk(JunkFilter *junkfilter, TupleTableSlot *slot)
{
    HeapTuple 	tuple;
    HeapTuple 	cleanTuple;
    AttrNumber 	*cleanMap;
    TupleDesc 	cleanTupType;
    TupleDesc	tupType;
    int 	cleanLength;
    bool 	isNull;
    int 	i;
    Size 	size;
    Datum 	*values;
    char	*nulls;
    Datum	values_array[64];
    char	nulls_array[64];
    
    /* ----------------
     *	get info from the slot and the junk filter
     * ----------------
     */
    tuple = slot->val;
    
    tupType = 		(TupleDesc) junkfilter->jf_tupType;
    cleanTupType = 	(TupleDesc) junkfilter->jf_cleanTupType;
    cleanLength = 	junkfilter->jf_cleanLength;
    cleanMap = 		junkfilter->jf_cleanMap;
    
    /* ---------------------
     *  Handle the trivial case first.
     * ---------------------
     */
    if (cleanLength == 0)
	return (HeapTuple) NULL;
    
    /* ---------------------
     * Create the arrays that will hold the attribute values
     * and the null information for the new "clean" tuple.
     *
     * Note: we use memory on the stack to optimize things when
     *       we are dealing with a small number of tuples.
     *	     for large tuples we just use palloc.
     * ---------------------
     */
    if (cleanLength > 64) {
	size = 	 cleanLength * sizeof(Datum);
	values = (Datum *) palloc(size);
	
	size = 	 cleanLength * sizeof(char);
	nulls =  (char *) palloc(size);
    } else {
	values = values_array;
	nulls =  nulls_array;
    }
    
    /* ---------------------
     * Exctract one by one all the values of the "clean" tuple.
     * ---------------------
     */
    for (i=0; i<cleanLength; i++) {
	Datum d = (Datum)
	    heap_getattr(tuple, InvalidBuffer, cleanMap[i], tupType, &isNull);
	
	values[i] = d;
	
	if (isNull)
	    nulls[i] = 'n';
	else
	    nulls[i] = ' ';
    }
    
    /* ---------------------
     * Now form the new tuple.
     * ---------------------
     */
    cleanTuple = heap_formtuple(cleanTupType,
				values,
				nulls);
    
    /* ---------------------
     * We are done.  Free any space allocated for 'values' and 'nulls'
     * and return the new tuple.
     * ---------------------
     */
    if (cleanLength > 64) {
	pfree(values);
	pfree(nulls);
    }
    
    return(cleanTuple);
}