/* -------------------------------------------------------------------------
 *
 * nodeBitmapAnd.cpp
 *	  routines to handle BitmapAnd nodes.
 *
 * Portions Copyright (c) 2020 Huawei Technologies Co.,Ltd.
 * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  src/gausskernel/runtime/executor/nodeBitmapAnd.cpp
 *
 * -------------------------------------------------------------------------
 *
 * INTERFACE ROUTINES
 *		ExecInitBitmapAnd	- initialize the BitmapAnd node
 *		MultiExecBitmapAnd	- retrieve the result bitmap from the node
 *		ExecEndBitmapAnd	- shut down the BitmapAnd node
 *		ExecReScanBitmapAnd - rescan the BitmapAnd node
 *
 *	 NOTES
 *		BitmapAnd nodes don't make use of their left and right
 *		subtrees, rather they maintain a list of subplans,
 *		much like Append nodes.  The logic is much simpler than
 *		Append, however, since we needn't cope with forward/backward
 *		execution.
 */
#include "postgres.h"
#include "knl/knl_variable.h"

#include "executor/execdebug.h"
#include "executor/nodeBitmapAnd.h"

/* ----------------------------------------------------------------
 *		ExecInitBitmapAnd
 *
 *		Begin all of the subscans of the BitmapAnd node.
 * ----------------------------------------------------------------
 */
BitmapAndState* ExecInitBitmapAnd(BitmapAnd* node, EState* estate, int eflags)
{
    BitmapAndState* bitmapandstate = makeNode(BitmapAndState);
    PlanState** bitmapplanstates;
    int nplans;
    int i;
    ListCell* l = NULL;
    Plan* initNode = NULL;

    /* check for unsupported flags */
    Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));

    /*
     * Set up empty vector of subplan states
     */
    nplans = list_length(node->bitmapplans);

    bitmapplanstates = (PlanState**)palloc0(nplans * sizeof(PlanState*));

    /*
     * create new BitmapAndState for our BitmapAnd node
     */
    bitmapandstate->ps.plan = (Plan*)node;
    bitmapandstate->ps.state = estate;
    bitmapandstate->bitmapplans = bitmapplanstates;
    bitmapandstate->nplans = nplans;

    /*
     * Miscellaneous initialization
     *
     * BitmapAnd plans don't have expression contexts because they never call
     * ExecQual or ExecProject.  They don't need any tuple slots either.
     */
    /*
     * call ExecInitNode on each of the plans to be executed and save the
     * results into the array "bitmapplanstates".
     */
    i = 0;
    foreach (l, node->bitmapplans) {
        initNode = (Plan*)lfirst(l);
        bitmapplanstates[i] = ExecInitNode(initNode, estate, eflags);
        i++;
    }

    return bitmapandstate;
}

/* ----------------------------------------------------------------
 *	   MultiExecBitmapAnd
 * ----------------------------------------------------------------
 */
Node* MultiExecBitmapAnd(BitmapAndState* node)
{
    PlanState** bitmapplans;
    int nplans;
    int i;
    TIDBitmap* result = NULL;

    /* must provide our own instrumentation support */
    if (node->ps.instrument) {
        InstrStartNode(node->ps.instrument);
    }

    /*
     * get information from the node
     */
    bitmapplans = node->bitmapplans;
    nplans = node->nplans;

    /*
     * Scan all the subplans and AND their result bitmaps
     */
    for (i = 0; i < nplans; i++) {
        PlanState* subnode = bitmapplans[i];
        subnode->hbktScanSlot.currSlot = node->ps.hbktScanSlot.currSlot;
        TIDBitmap* subresult = NULL;

        subresult = (TIDBitmap*)MultiExecProcNode(subnode);
        if (subresult == NULL || !IsA(subresult, TIDBitmap))
            ereport(ERROR,
                (errcode(ERRCODE_UNRECOGNIZED_NODE_TYPE),
                    errmodule(MOD_EXECUTOR),
                    errmsg("unrecognized result from subplan for BitmapAnd.")));

        if (result == NULL) {
            result = subresult; /* first subplan */
        } else {
            tbm_intersect(result, subresult);
            tbm_free(subresult);
        }

        /*
         * If at any stage we have a completely empty bitmap, we can fall out
         * without evaluating the remaining subplans, since ANDing them can no
         * longer change the result.  (Note: the fact that indxpath.c orders
         * the subplans by selectivity should make this case more likely to
         * occur.)
         */
        if (tbm_is_empty(result)) {
            break;
        }
    }

    if (result == NULL) {
        ereport(ERROR,
            (errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
                errmodule(MOD_EXECUTOR),
                errmsg("BitmapAnd doesn't support zero inputs")));
    }

    /* must provide our own instrumentation support */
    if (node->ps.instrument) {
        InstrStopNode(node->ps.instrument, 0 /* XXX */);
    }

    return (Node*)result;
}

/* ----------------------------------------------------------------
 *		ExecEndBitmapAnd
 *
 *		Shuts down the subscans of the BitmapAnd node.
 *
 *		Returns nothing of interest.
 * ----------------------------------------------------------------
 */
void ExecEndBitmapAnd(BitmapAndState* node)
{
    PlanState** bitmapplans;
    int nplans;
    int i;

    /*
     * get information from the node
     */
    bitmapplans = node->bitmapplans;
    nplans = node->nplans;

    /*
     * shut down each of the subscans (that we've initialized)
     */
    for (i = 0; i < nplans; i++) {
        if (bitmapplans[i])
            ExecEndNode(bitmapplans[i]);
    }
}

void ExecReScanBitmapAnd(BitmapAndState* node)
{
    int i;

    for (i = 0; i < node->nplans; i++) {
        PlanState* subnode = node->bitmapplans[i];

        /*
         * ExecReScan doesn't know about my subplans, so I have to do
         * changed-parameter signaling myself.
         */
        if (node->ps.chgParam != NULL)
            UpdateChangedParamSet(subnode, node->ps.chgParam);

        /*
         * If chgParam of subnode is not null then plan will be re-scanned by
         * first ExecProcNode.
         */
        if (subnode->chgParam == NULL)
            ExecReScan(subnode);
    }
}