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From: Richard Guo <[email protected]>
To: Tom Lane <[email protected]>
Cc: Pg Hackers <[email protected]>
Cc: Finnerty, Jim <[email protected]>
Subject: Re: Making Vars outer-join aware
Date: Tue, 30 Aug 2022 11:21:42 +0800
Message-ID: <CAMbWs4_WNcvQGiFMLJanj3h6WMzFi6P-=bifmnuXUcg4PSXQgA@mail.gmail.com> (raw)
In-Reply-To: <CAMbWs4-mvPPCJ1W6iK6dD5HiNwoJdi6mZp=-7mE8N9Sh+cd0tQ@mail.gmail.com>
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On Mon, Aug 29, 2022 at 2:30 PM Richard Guo <[email protected]> wrote:

>
> On Fri, Aug 19, 2022 at 2:45 AM Tom Lane <[email protected]> wrote:
>
>> Here's a rebase up to HEAD, mainly to get the cfbot back in sync
>> as to what's the live patch.
>
>
> Noticed another different behavior from previous. When we try to reduce
> JOIN_LEFT to JOIN_ANTI, we want to know if the join's own quals are
> strict for any Var that was forced null by higher qual levels. We do
> that by checking whether local_nonnullable_vars and forced_null_vars
> overlap. However, the same Var from local_nonnullable_vars and
> forced_null_vars may be labeled with different varnullingrels. If that
> is the case, currently we would fail to tell they actually overlap.
>

I wonder why this is not noticed by regression tests. So I did some
search and it seems we do not have any test cases covering the
transformation we apply to reduce outer joins. I think maybe we should
add such cases in regression tests.

Thanks
Richard


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