Horton

Re: Change GUC hashtable to use simplehash?

Jeff Davis <pgsql@j-davis.com>

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From: Jeff Davis <pgsql@j-davis.com>
To: Gurjeet Singh <gurjeet@singh.im>
Cc: pgsql-hackers@postgresql.org
Date: 2023-11-17T21:44:21Z
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

On Fri, 2023-11-17 at 13:22 -0800, Gurjeet Singh wrote:
> This is not a comment on the patch itself, but since GUC operations
> are not typically considered performance or space sensitive,

A "SET search_path" clause on a CREATE FUNCTION is a case for better
performance in guc.c, because it repeatedly sets and rolls back the
setting on each function invocation.

Unfortunately, this patch doesn't really improve the performance. The
reason the hash table in guc.c is slow is because of the case folding
in both hashing and comparison. I might get around to fixing that,
which could have a minor impact, and perhaps then the choice between
hsearch/simplehash would matter.

> this
> comment from simplehash.h makes a case against it.
> 
>  *      It's probably not worthwhile to generate such a specialized
> implementation
>  *      for hash tables that aren't performance or space sensitive.
> 
> But your argument of a nicer API might make a case for the patch.

Yeah, that's what I was thinking. simplehash is newer and has a nicer
API, so if we like it and want to move more code over, this is one
step. But if we are fine using both hsearch.h and simplehash.h for
overlapping use cases indefinitely, then I'll drop this.

Regards,
	Jeff Davis