Function streamIteratorRemoveEntry

app/redis-6.2.6/src/t_stream.c:1260–1311

Remove the current entry from the stream: can be called after the * GetID() API or after any GetField() call, however we need to iterate * a valid entry while calling this function. Moreover the function * requires the entry ID we are currently iterating, that was previously * returned by GetID(). * * Note that after calling this function, next calls to GetField() can't * be performed: the

 * automatically re-seek to the next entry, so the caller should continue
 * with GetID(). */
void streamIteratorRemoveEntry(streamIterator *si, streamID *current) {
    unsigned char *lp = si->lp;
    int64_t aux;

    /* We do not really delete the entry here. Instead we mark it as
     * deleted flagging it, and also incrementing the count of the
     * deleted entries in the listpack header.
     *
     * We start flagging: */
    int flags = lpGetInteger(si->lp_flags);
    flags |= STREAM_ITEM_FLAG_DELETED;
    lp = lpReplaceInteger(lp,&si->lp_flags,flags);

    /* Change the valid/deleted entries count in the master entry. */
    unsigned char *p = lpFirst(lp);
    aux = lpGetInteger(p);

    if (aux == 1) {
        /* If this is the last element in the listpack, we can remove the whole
         * node. */
        lpFree(lp);
        raxRemove(si->stream->rax,si->ri.key,si->ri.key_len,NULL);
    } else {
        /* In the base case we alter the counters of valid/deleted entries. */
        lp = lpReplaceInteger(lp,&p,aux-1);
        p = lpNext(lp,p); /* Seek deleted field. */
        aux = lpGetInteger(p);
        lp = lpReplaceInteger(lp,&p,aux+1);

        /* Update the listpack with the new pointer. */
        if (si->lp != lp)
            raxInsert(si->stream->rax,si->ri.key,si->ri.key_len,lp,NULL);
    }

    /* Update the number of entries counter. */
    si->stream->length--;

    /* Re-seek the iterator to fix the now messed up state. */
    streamID start, end;
    if (si->rev) {
        streamDecodeID(si->start_key,&start);
        end = *current;
    } else {
        start = *current;
        streamDecodeID(si->end_key,&end);
    }
    streamIteratorStop(si);
    streamIteratorStart(si,si->stream,&start,&end,si->rev);

    /* TODO: perform a garbage collection here if the ration between
     * deleted and valid goes over a certain limit. */
}

/* Stop the stream iterator. The only cleanup we need is to free the rax
 * iterator, since the stream iterator itself is supposed to be stack