Function streamRewriteTrimArgument

app/redis-6.2.6/src/t_stream.c:1770–1782

We propagate MAXLEN/MINID ~ as MAXLEN/MINID = * otherwise trimming is no longer deterministic on replicas / AOF. */

/* We propagate MAXLEN/MINID ~ <count> as MAXLEN/MINID = <resulting-len-of-stream>
 * otherwise trimming is no longer deterministic on replicas / AOF. */
void streamRewriteTrimArgument(client *c, stream *s, int trim_strategy, int idx) {
    robj *arg;
    if (trim_strategy == TRIM_STRATEGY_MAXLEN) {
        arg = createStringObjectFromLongLong(s->length);
    } else {
        streamID first_id;
        streamGetEdgeID(s, 1, &first_id);
        arg = createObjectFromStreamID(&first_id);
    }

    rewriteClientCommandArgument(c,idx,arg);
    decrRefCount(arg);
}

/* XADD key [(MAXLEN [~|=] <count> | MINID [~|=] <id>) [LIMIT <entries>]] [NOMKSTREAM] <ID or *> [field value] [field value] ... */
void xaddCommand(client *c) {