Regarding to **L.window_start = R.window_start AND L.window_end = R.window_end**:
In general, the current table function windowing model is to append window metadata to table directly, thus window metadata becomes a part of table (or call it data). So as a part of table, these two columns should be treated as normal columns thus they should be in the join on condition. If you want to make it optional, it makes window start/end columns special and has a semantic binding with special table functions (TUMBLE, HOP, SESSION), which then becomes really not a SQL thing. For example, we can allow users to define their own windowing table function. In that case, how will you utilize window start/end produced by a customized windowing table function? What if users produce wired windows that have overlapped window starts or window ends? Keeping windows start/end as a part of the table, treating them no different from other columns, could give a consistent behavior for either built-in table function or user-defined table function. If you think it is too verbose, there are two options to optimize: 1. for TUMBLE/HOP/SESSION, to identify a unique window, you will only need either window start or end, so you can simplify it, for example, to L.window_start = R.window_start only. 2. (not recommended), you can cut off **L.window_start = R.window_start AND L.window_end = R.window_end**, but add window metadata comparison to join implicitly by execution engine. E.g. you can make up the join condition in your JoinRel if two inputs are TUMBLE. -Rui On Tue, Sep 22, 2020 at 10:27 PM Danny Chan <yuzhao....@gmail.com> wrote: > Yes, the red part is **L.window_start = R.window_start AND L.window_end = > R.window_end** > > > Is this a limitation for "triggered by the watermark of the stream”? > > No, because in most of the cases, there is no need to output the > intermediate/partial join records then send retractions. > > > So, how do you think about the condition syntax **L.window_start = > R.window_start AND L.window_end = R.window_end** ? > > Best, > Danny Chan > 在 2020年9月23日 +0800 PM12:47，dev@calcite.apache.org，写道： > > > > L.window_start = R.window_start AND L.window_end = R.window_end >
