| 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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| Lists: | pgsql-hackers |
>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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