From: | Emre Hasegeli <emre(at)hasegeli(dot)com> |
---|---|
To: | Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> |
Cc: | Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: constraint exclusion and nulls in IN (..) clause |
Date: | 2018-03-06 09:46:42 |
Message-ID: | CAE2gYzzaemeKJ7WbBt0eR9U-w4v0aDQ-pFNPpEbdRf_dUvMkOw@mail.gmail.com |
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Lists: | pgsql-hackers |
> Patch teaches it to ignore nulls when it's known that the operator being
> used is strict. It is harmless and has the benefit that constraint
> exclusion gives an answer that is consistent with what actually running
> such a qual against a table's rows would do.
Yes, I understood that. I just meant that I don't know if it is the
best way to skip NULLs inside "next_fn". Maybe the caller of the
"next_fn"s should skip them. Anyway, the committer can judge this
better.
> Yeah. Rearranged the code to fix that.
This version looks correct to me.
> + state->next = (state->next != NULL) ? lnext(state->next) : NULL;
> + node = (state->next != NULL) ? lfirst(state->next) : NULL;
I think it is unnecessary to check for (state->next != NULL) two
times. We can put those in a single if.
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