Horton

Re: Change GUC hashtable to use simplehash?

John Naylor <johncnaylorls@gmail.com>

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From: John Naylor <johncnaylorls@gmail.com>
To: Jeff Davis <pgsql@j-davis.com>
Cc: Ants Aasma <ants.aasma@cybertec.at>, Heikki Linnakangas <hlinnaka@iki.fi>, Junwang Zhao <zhjwpku@gmail.com>, jian he <jian.universality@gmail.com>, Andres Freund <andres@anarazel.de>, Tom Lane <tgl@sss.pgh.pa.us>, Gurjeet Singh <gurjeet@singh.im>, pgsql-hackers@postgresql.org
Date: 2024-04-07T01:40:15Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Silence warning in older versions of Valgrind

  2. Revert "Speed up tail processing when hashing aligned C strings, take two"

  3. Speed up tail processing when hashing aligned C strings, take two

  4. Teach fasthash_accum to use platform endianness for bytewise loads

  5. Add macro to disable address safety instrumentation

  6. Convert uses of hash_string_pointer to fasthash equivalent

  7. Speed up tail processing when hashing aligned C strings

  8. Add helper functions for dshash tables with string keys.

  9. Fix warnings in cpluspluscheck

  10. Further cosmetic review of hashfn_unstable.h

  11. Simplify initialization of incremental hash state

  12. Add optimized C string hashing

  13. Add inline incremental hash functions for in-memory use

  14. Make all Perl warnings fatal

Attachments

On Tue, Jan 30, 2024 at 4:13 AM Ants Aasma <ants.aasma@cybertec.at> wrote:
>
> But given that we know the data length and we have it in a register
> already, it's easy enough to just mask out data past the end with a
> shift. See patch 1. Performance benefit is about 1.5x Measured on a
> small test harness that just hashes and finalizes an array of strings,
> with a data dependency between consecutive hashes (next address
> depends on the previous hash output).

I pushed this with a couple cosmetic adjustments, after fixing the
endianness issue. I'm not sure why valgrind is fine with this way, and
the other ways I tried forming the (little-endian) mask raised errors.
In addition to "zero_byte_low | (zero_byte_low - 1)", I tried
"~zero_byte_low & (zero_byte_low - 1)" and "zero_byte_low ^
(zero_byte_low - 1)" to no avail.

On Thu, Mar 28, 2024 at 12:37 PM Jeff Davis <pgsql@j-davis.com> wrote:
> 0001 looks good to me, thank you.
>
> > v21-0003 adds a new file hashfn_unstable.c for convenience functions
> > and converts all the duplicate frontend uses of hash_string_pointer.
>
> Why not make hash_string() inline, too? I'm fine with it either way,
> I'm just curious why you went to the trouble to create a new .c file so
> it didn't have to be inlined.

Thanks for looking! I pushed these, with hash_string() inlined.

I've attached (not reindented for clarity) an update of something
mentioned a few times already -- removing strlen calls for dynahash
and dshash string keys. I'm not quite sure how the comments should be
updated about string_hash being deprecated to call directly. This
patch goes further and semi-deprecates calling it at all, so these
comments seem a bit awkward now.