Re: check for null value before looking up the hash function

From: Ranier Vilela <ranier(dot)vf(at)gmail(dot)com>
To: Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: check for null value before looking up the hash function
Date: 2022-05-21 13:06:36
Message-ID: CAEudQApKr6XEeK1O7RAO3=si7Y3a0kdhyRinKZUpNEV+w9aYrA@mail.gmail.com
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>Zhihong Yu <zyu(at)yugabyte(dot)com> writes:
>> I was looking at the code in hash_record()
>> of src/backend/utils/adt/rowtypes.c
>> It seems if nulls[i] is true, we don't need to look up the hash function.

>I don't think this is worth changing. It complicates the logic,
>rendering it unlike quite a few other functions written in the same
>style. In cases where the performance actually matters, the hash
>function is cached across multiple calls anyway. You might save
>something if you have many calls in a query and not one of them
>receives a non-null input, but how likely is that?

I disagree.
I think that is worth changing. The fact of complicating the logic
is irrelevant.
But maybe the v2 attached would be a little better.
My doubt is the result calc when nulls are true.

regards,
Ranier Vilela

Attachment Content-Type Size
v2-hash-record-check-null-first.patch application/octet-stream 2.2 KB

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