postgresql/src/backend/executor/nodeAgg.c

/*-------------------------------------------------------------------------
 *
 * nodeAgg.c--
 *    Routines to handle aggregate nodes. 
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * NOTE
 *    The implementation of Agg node has been reworked to handle legal
 *    SQL aggregates. (Do not expect POSTQUEL semantics.)    -- ay 2/95
 *
 * IDENTIFICATION
 *    /usr/local/devel/pglite/cvs/src/backend/executor/nodeAgg.c,v 1.13 1995/08/01 20:19:07 jolly Exp
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/heapam.h"
#include "catalog/pg_aggregate.h"
#include "catalog/catalog.h"
#include "executor/executor.h"
#include "executor/nodeAgg.h"
#include "storage/bufmgr.h"
#include "utils/palloc.h"
#include "parser/catalog_utils.h"

/*
 * AggFuncInfo -
 *    keeps the transition functions information around
 */
typedef struct AggFuncInfo {
    Oid		xfn1_oid;
    Oid		xfn2_oid;
    Oid		finalfn_oid;
    func_ptr	xfn1;
    func_ptr	xfn2;
    func_ptr	finalfn;
    int		xfn1_nargs;
    int		xfn2_nargs;
    int		finalfn_nargs;
} AggFuncInfo;

static Datum aggGetAttr(TupleTableSlot *tuple, Aggreg *agg, bool *isNull);


/* ---------------------------------------
 *
 * ExecAgg -
 *
 *    ExecAgg receives tuples from its outer subplan and aggregates over
 *    the appropriate attribute for each (unique) aggregate in the target
 *    list. (The number of tuples to aggregate over depends on whether a
 *    GROUP BY clause is present. It might be the number of tuples in a
 *    group or all the tuples that satisfy the qualifications.) The value of
 *    each aggregate is stored in the expression context for ExecProject to
 *    evaluate the result tuple.
 *    
 *    ExecAgg evaluates each aggregate in the following steps: (initcond1,
 *    initcond2 are the initial values and sfunc1, sfunc2, and finalfunc are
 *    the transition functions.)
 *
 *       value1[i] = initcond1
 *       value2[i] = initcond2
 *       forall tuples do 
 *	    value1[i] = sfunc1(aggregate_attribute, value1[i])
 *	    value2[i] = sfunc2(value2[i])
 * 	 value1[i] = finalfunc(value1[i], value2[i])
 *
 *    If the outer subplan is a Group node, ExecAgg returns as many tuples
 *    as there are groups.
 *
 *    XXX handling of NULL doesn't work
 *
 *    OLD COMMENTS
 *
 *	XXX Aggregates should probably have another option: what to do 
 *	with transfn2 if we hit a null value.  "count" (transfn1 = null,
 *	transfn2 = increment) will want to have transfn2 called; "avg"
 *	(transfn1 = add, transfn2 = increment) will not. -pma 1/3/93
 *
 * ------------------------------------------
 */
TupleTableSlot *
ExecAgg(Agg *node)
{
    AggState		*aggstate;
    EState		*estate;
    Aggreg		**aggregates;
    Plan		*outerPlan;
    int			i, nagg;
    Datum		*value1, *value2;
    int			*noInitValue;
    AggFuncInfo		*aggFuncInfo;
    long		nTuplesAgged = 0;
    ExprContext		*econtext;
    ProjectionInfo	*projInfo;
    TupleTableSlot	*resultSlot;
    HeapTuple		oneTuple;
    char*               nulls;
    bool		isDone;
    bool		isNull = FALSE, isNull1 = FALSE, isNull2 = FALSE;

    /* ---------------------
     *  get state info from node
     * ---------------------
     */
    aggstate = node->aggstate;
    if (aggstate->agg_done)
	return NULL;

    estate = node->plan.state;
    econtext = aggstate->csstate.cstate.cs_ExprContext;
    aggregates = node->aggs;
    nagg = node->numAgg;

    value1 = node->aggstate->csstate.cstate.cs_ExprContext->ecxt_values;
    nulls = node->aggstate->csstate.cstate.cs_ExprContext->ecxt_nulls;

    value2 = (Datum *)palloc(sizeof(Datum) * nagg);
    memset(value2, 0, sizeof(Datum) * nagg);

    aggFuncInfo = (AggFuncInfo *)palloc(sizeof(AggFuncInfo) * nagg);
    memset(aggFuncInfo, 0, sizeof(AggFuncInfo) * nagg);

    noInitValue = (int *)palloc(sizeof(int) * nagg);
    memset(noInitValue, 0, sizeof(noInitValue) * nagg);
    
    outerPlan = outerPlan(node);
    oneTuple = NULL;
    
    projInfo = aggstate->csstate.cstate.cs_ProjInfo;

    for(i = 0; i < nagg; i++) {
	Aggreg 		*agg;
	char            *aggname;
	HeapTuple	aggTuple;
	Form_pg_aggregate  aggp;
	Oid		xfn1_oid, xfn2_oid, finalfn_oid;
	func_ptr	xfn1_ptr, xfn2_ptr, finalfn_ptr;
	int		xfn1_nargs, xfn2_nargs, finalfn_nargs;

	agg = aggregates[i];

	/* ---------------------
	 *  find transfer functions of all the aggregates and initialize
	 *  their initial values
	 * ---------------------
	 */
	aggname = agg->aggname;
	aggTuple = SearchSysCacheTuple(AGGNAME, 
				       PointerGetDatum(aggname),
				       ObjectIdGetDatum(agg->basetype),
				       0,0);
	if (!HeapTupleIsValid(aggTuple))
	    elog(WARN, "ExecAgg: cache lookup failed for aggregate \"%s\"(%s)",
		 aggname,
		 tname(get_id_type(agg->basetype)));
	aggp = (Form_pg_aggregate) GETSTRUCT(aggTuple);

	xfn1_oid = aggp->aggtransfn1;
	xfn2_oid = aggp->aggtransfn2;
	finalfn_oid = aggp->aggfinalfn;
    
	if (OidIsValid(finalfn_oid)) {
	    fmgr_info(finalfn_oid, &finalfn_ptr, &finalfn_nargs);
	    aggFuncInfo[i].finalfn_oid = finalfn_oid;
	    aggFuncInfo[i].finalfn = finalfn_ptr;
	    aggFuncInfo[i].finalfn_nargs = finalfn_nargs;
	}

	if (OidIsValid(xfn2_oid)) {
	    fmgr_info(xfn2_oid, &xfn2_ptr, &xfn2_nargs);
	    aggFuncInfo[i].xfn2_oid = xfn2_oid;
	    aggFuncInfo[i].xfn2 = xfn2_ptr;
	    aggFuncInfo[i].xfn2_nargs = xfn2_nargs;
	    value2[i] = (Datum)AggNameGetInitVal((char*)aggname,
						 aggp->aggbasetype,
						 2,
						 &isNull2);
	    /* ------------------------------------------
	     * If there is a second transition function, its initial
	     * value must exist -- as it does not depend on data values,
	     * we have no other way of determining an initial value.
	     * ------------------------------------------
	     */
	    if (isNull2)
		elog(WARN, "ExecAgg: agginitval2 is null");
	}

	if (OidIsValid(xfn1_oid)) {
	    fmgr_info(xfn1_oid, &xfn1_ptr, &xfn1_nargs);
	    aggFuncInfo[i].xfn1_oid = xfn1_oid;
	    aggFuncInfo[i].xfn1 = xfn1_ptr;
	    aggFuncInfo[i].xfn1_nargs = xfn1_nargs;
	    value1[i] = (Datum)AggNameGetInitVal((char*)aggname,
						 aggp->aggbasetype,
						 1,
						 &isNull1);

	    /* ------------------------------------------
	     * If the initial value for the first transition function
	     * doesn't exist in the pg_aggregate table then we let
	     * the first value returned from the outer procNode become
	     * the initial value. (This is useful for aggregates like
	     * max{} and min{}.)
	     * ------------------------------------------
	     */
	    if (isNull1) {
		noInitValue[i] = 1;
		nulls[i] = 1;
	    }
	}
    }

    /* ----------------
     *   for each tuple from the the outer plan, apply all the aggregates
     * ----------------
     */
    for (;;) {
	HeapTuple outerTuple = NULL;
	TupleTableSlot *outerslot;
	
	isNull = isNull1 = isNull2 = 0;
	outerslot = ExecProcNode(outerPlan, (Plan*)node);
	if (outerslot) outerTuple = outerslot->val;
	if (!HeapTupleIsValid(outerTuple)) {
	    /* when the outerplan doesn't return a single tuple,
	       create a dummy heaptuple anyway
	       because we still need to return a valid aggregate value.
	       The value returned will be the initial values of the
	       transition functions */
	    if (nTuplesAgged == 0) {
		TupleDesc tupType;
		Datum *tupValue;
		char* null_array;

		tupType = aggstate->csstate.css_ScanTupleSlot->ttc_tupleDescriptor;
		tupValue = 	projInfo->pi_tupValue;
		
		/* initially, set all the values to NULL */
		null_array = malloc(tupType->natts);
		for (i=0;i<tupType->natts;i++)
		    null_array[i] = 'n';
		oneTuple = heap_formtuple(tupType, tupValue, null_array);
		free(null_array);
	    }
	    break;
	}

	for(i = 0; i < nagg; i++) {
	    AttrNumber attnum;
	    int2 attlen;
	    Datum newVal;
	    AggFuncInfo *aggfns = &aggFuncInfo[i];
	    Datum args[2];

	    newVal = aggGetAttr(outerslot,
				aggregates[i],
				&isNull);

	    if (isNull)
		continue;	/* ignore this tuple for this agg */

	    if (aggfns->xfn1) {
		if (noInitValue[i]) {
		    /*
		     * value1 and value2 has not been initialized. This
		     * is the first non-NULL value. We use it as the
		     * initial value.
		     */
		     /* but we can't just use it straight, we have
			to make a copy of it since the tuple from which
			it came will be freed on the next iteration 
			of the scan */
		    attnum = ((Var*)aggregates[i]->target)->varattno;
		    attlen = outerslot->ttc_tupleDescriptor->attrs[attnum-1]->attlen;
		    if (attlen == -1)  {
			/* variable length */
			attlen = VARSIZE((struct varlena*) newVal);
		    }
		    value1[i] = (Datum)palloc(attlen);
                 if (outerslot->ttc_tupleDescriptor->attrs[attnum-1]->attbyval)
                        value1[i] = newVal;
                    else
                        memmove((char*) (value1[i]), (char*) (newVal), attlen);
		    /* value1[i] = newVal; */
		    noInitValue[i] = 0;
		    nulls[i] = 0;
		} else {
		    /*
		     * apply the transition functions.
		     */
		    args[0] = value1[i];
		    args[1] = newVal;
		    value1[i] =
			(Datum)fmgr_c(aggfns->xfn1, aggfns->xfn1_oid,
				      aggfns->xfn1_nargs, (FmgrValues *)args,
				      &isNull1);
		    Assert(!isNull1);
		}
	    }

	    if (aggfns->xfn2) {
		Datum xfn2_val = value2[i];
		
		value2[i] =
		    (Datum)fmgr_c(aggfns->xfn2, aggfns->xfn2_oid,
				  aggfns->xfn2_nargs,
				  (FmgrValues *)&xfn2_val, &isNull2);
		Assert(!isNull2);
	    }
	}

	/*
	 * keep this for the projection (we only need one of these -
	 * all the tuples we aggregate over share the same group column)
	 */
	if (!oneTuple) {
	    oneTuple = heap_copytuple(outerslot->val);
	}

	nTuplesAgged++;
    }

    /* --------------
     * finalize the aggregate (if necessary), and get the resultant value
     * --------------
     */
    for(i = 0; i < nagg; i++) {
	char *args[2];
	AggFuncInfo *aggfns = &aggFuncInfo[i];
	
 	if (aggfns->finalfn && nTuplesAgged > 0) { 
	    if (aggfns->finalfn_nargs > 1) {
		args[0] = (char*)value1[i];
		args[1] = (char*)value2[i];
	    } else if (aggfns->xfn1) {
		args[0] = (char*)value1[i];
	    } else if (aggfns->xfn2) {
		args[0] = (char*)value2[i];
	    } else
		elog(WARN, "ExecAgg: no valid transition functions??");
	    value1[i] =
		(Datum)fmgr_c(aggfns->finalfn, aggfns->finalfn_oid,
			      aggfns->finalfn_nargs, (FmgrValues *) args,
			      &(nulls[i]));
	} else if (aggfns->xfn1) {
	    /*
	     * value in the right place, ignore. (If you remove this
	     * case, fix the else part. -ay 2/95)
	     */
	} else if (aggfns->xfn2) {
	    value1[i] = value2[i];
	} else
	    elog(WARN, "ExecAgg: no valid transition functions??");
    }

    /*
     * whether the aggregation is done depends on whether we are doing
     * aggregation over groups or the entire table
     */
    if (nodeTag(outerPlan)==T_Group) {
	/* aggregation over groups */
	aggstate->agg_done = ((Group*)outerPlan)->grpstate->grp_done;
    } else {
	aggstate->agg_done = TRUE;
    }

    /* ----------------
     *	form a projection tuple, store it in the result tuple
     *  slot and return it.
     * ----------------
     */
    ExecStoreTuple(oneTuple,
		   aggstate->csstate.css_ScanTupleSlot,
		   InvalidBuffer,
		   false);
    econtext->ecxt_scantuple = aggstate->csstate.css_ScanTupleSlot;
    resultSlot = ExecProject(projInfo, &isDone);

    if (oneTuple)
	pfree(oneTuple);
    
    return resultSlot;
}

/* -----------------
 * ExecInitAgg
 *
 *  Creates the run-time information for the agg node produced by the
 *  planner and initializes its outer subtree
 * -----------------
 */
bool
ExecInitAgg(Agg *node, EState *estate, Plan *parent)
{
    AggState		*aggstate;
    Plan		*outerPlan;
    ExprContext		*econtext;
    
    /* 
     * assign the node's execution state
     */
    node->plan.state = estate;
    
    /*
     * create state structure
     */
    aggstate = makeNode(AggState);
    node->aggstate = aggstate;
    aggstate->agg_done = FALSE;

    /*
     * assign node's base id and create expression context
     */
    ExecAssignNodeBaseInfo(estate, &aggstate->csstate.cstate,
			   (Plan*) parent);
    ExecAssignExprContext(estate, &aggstate->csstate.cstate);
    
#define AGG_NSLOTS 2
    /*
     * tuple table initialization
     */
    ExecInitScanTupleSlot(estate, &aggstate->csstate);
    ExecInitResultTupleSlot(estate, &aggstate->csstate.cstate);

    econtext = aggstate->csstate.cstate.cs_ExprContext;
    econtext->ecxt_values =
	(Datum *)palloc(sizeof(Datum) * node->numAgg);
    memset(econtext->ecxt_values, 0, sizeof(Datum) * node->numAgg);
    econtext->ecxt_nulls = (char *)palloc(node->numAgg);
    memset(econtext->ecxt_nulls, 0, node->numAgg);

    /*
     * initializes child nodes
     */
    outerPlan = outerPlan(node);
    ExecInitNode(outerPlan, estate, (Plan *)node);
    
    /* ----------------
     * 	initialize tuple type.
     * ----------------
     */
    ExecAssignScanTypeFromOuterPlan((Plan *) node, &aggstate->csstate); 

    /*
     * Initialize tuple type for both result and scan.
     * This node does no projection
     */
    ExecAssignResultTypeFromTL((Plan*) node, &aggstate->csstate.cstate);
    ExecAssignProjectionInfo((Plan*)node, &aggstate->csstate.cstate);

    return TRUE;
}

int
ExecCountSlotsAgg(Agg *node)
{
    return ExecCountSlotsNode(outerPlan(node)) +
	ExecCountSlotsNode(innerPlan(node)) +
	    AGG_NSLOTS;
}

/* ------------------------
 *	ExecEndAgg(node)
 *
 * -----------------------
 */
void
ExecEndAgg(Agg *node)
{
    AggState	*aggstate;
    Plan	*outerPlan;

    aggstate = node->aggstate;

    ExecFreeProjectionInfo(&aggstate->csstate.cstate);

    outerPlan = outerPlan(node);
    ExecEndNode(outerPlan, (Plan*)node);
    
    /* clean up tuple table */
    ExecClearTuple(aggstate->csstate.css_ScanTupleSlot);
}


/*****************************************************************************
 *  Support Routines
 *****************************************************************************/

/*
 * aggGetAttr -
 *    get the attribute (specified in the Var node in agg) to aggregate 
 *    over from the tuple
 */
static Datum
aggGetAttr(TupleTableSlot *slot,
	   Aggreg *agg,
	   bool *isNull)
{
    Datum	result;
    AttrNumber 	attnum;
    HeapTuple	heapTuple;
    TupleDesc	tuple_type;
    Buffer 	buffer;

    /* ----------------
     *   extract tuple information from the slot
     * ----------------
     */
    heapTuple =  slot->val;
    tuple_type = slot->ttc_tupleDescriptor;
    buffer =	 slot->ttc_buffer;
    
    attnum =  	((Var*)agg->target)->varattno;
    
    /*
     * If the attribute number is invalid, then we are supposed to
     * return the entire tuple, we give back a whole slot so that
     * callers know what the tuple looks like.
     */
    if (attnum == InvalidAttrNumber) {
	TupleTableSlot  *tempSlot;
	TupleDesc td;
	HeapTuple tup;
	
	tempSlot = makeNode(TupleTableSlot);
	tempSlot->ttc_shouldFree = false;
	tempSlot->ttc_descIsNew = true;
	tempSlot->ttc_tupleDescriptor = (TupleDesc)NULL,
	tempSlot->ttc_buffer = InvalidBuffer;
	tempSlot->ttc_whichplan = -1;
	
	tup = heap_copytuple(slot->val);
	td = CreateTupleDescCopy(slot->ttc_tupleDescriptor);
	
	ExecSetSlotDescriptor(tempSlot, td);
	
	ExecStoreTuple(tup, tempSlot, InvalidBuffer, true);
	return (Datum) tempSlot;
    }
    
    result =  (Datum)
      heap_getattr(heapTuple,  /* tuple containing attribute */
		   buffer,     /* buffer associated with tuple */
		   attnum,     /* attribute number of desired attribute */
		   tuple_type, /* tuple descriptor of tuple */
		   isNull);    /* return: is attribute null? */
    
    /* ----------------
     *	return null if att is null
     * ----------------
     */
    if (*isNull)
	return (Datum) NULL;
    
    return result;
}