I agree. For whoever fixes the JDBC adapter, I discovered this table describing alternative syntax on Oracle, DB2, MySQL: https://modern-sql.com/feature/is-distinct-from#proprietary-alternantives <https://modern-sql.com/feature/is-distinct-from#proprietary-alternantives>
Julian > On Jun 5, 2019, at 5:34 PM, Haisheng Yuan <[email protected]> wrote: > > > if sending SQL to a database that does not understand IS NOT DISTINCT FROM > That is sadly true. I found that Hive just starts to support INDF since > 3.0.0. But dy default expanding INDF is still questionable. Their > incapability should not force Calcite expand INDF by default. > > > If both arguments are not null, it probably makes sense to rewrite “x IS > > NOT DISTINCT FROM y” to “x = y”, > I agree. But it is can be done with RexSimplify easily, expanding it or using > a rule FilterRemoveIsNotDistinctFromRule is an overkill, IMHO. > > - Haisheng > > ------------------------------------------------------------------ > 发件人：Julian Hyde<[email protected]> > 日 期：2019年06月06日 05:09:14 > 收件人：dev<[email protected]> > 主 题：Re: [DISCUSS] IS NOT DISTINCT FROM rewrite > > My instinct is that we should leave it unexpanded. And that we should > recognize “equals-like operators”, so that a planner rule originally written > for ‘=‘ could easily be expanded to also apply to ‘is not distinct from’. > > Of course there would be a way of expanding it that we could use if > circumstances required it — e.g. if sending SQL to a database that does not > understand IS NOT DISTINCT FROM — but we would not expand it by default. > > If both arguments are not null, it probably makes sense to rewrite “x IS NOT > DISTINCT FROM y” to “x = y”, because the latter is more common and no less > simple. > > Julian > > > > > On Jun 5, 2019, at 1:46 PM, Haisheng Yuan <[email protected]> wrote: > > > > I see INDF is rewritten to OR, and FilterRemoveIsNotDistinctFromRule > > rewrites INDF to CASE expression. Why do we want to do that? To simplify > > expression like "a is not distinct from b or a = b"? Then we spend a lot > > effort to convert OR/CASE back to INDF. > > > > I am curious what is the motivation to rewrite INDF. Does it really help a > > lot in production? I would like to hear the use cases if it does. > > > > - Haisheng > >
