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[PATCH v6 3/3] Optimize hash function 2+ messages / 2 participants [nested] [flat]
* [PATCH v6 3/3] Optimize hash function @ 2021-01-20 22:06 Heikki Linnakangas <[email protected]> 0 siblings, 0 replies; 2+ messages in thread From: Heikki Linnakangas @ 2021-01-20 22:06 UTC (permalink / raw) --- src/backend/utils/resowner/resowner.c | 24 ++++++++++++++++++------ src/include/common/hashfn.h | 15 +++++++++++++++ 2 files changed, 33 insertions(+), 6 deletions(-) diff --git a/src/backend/utils/resowner/resowner.c b/src/backend/utils/resowner/resowner.c index 1db1e7cf14b..72e4d8a784c 100644 --- a/src/backend/utils/resowner/resowner.c +++ b/src/backend/utils/resowner/resowner.c @@ -163,15 +163,27 @@ static void ReleaseAuxProcessResourcesCallback(int code, Datum arg); * INTERNAL ROUTINES * *****************************************************************************/ +/* + * Hash function for value+kind combination. + */ static inline uint32 hash_resource_elem(Datum value, ResourceOwnerFuncs *kind) { - Datum data[2]; - - data[0] = value; - data[1] = PointerGetDatum(kind); - - return hash_bytes((unsigned char *) &data, 2 * SIZEOF_DATUM); + /* + * Most resources types store a pointer in 'value', and pointers are + * unique all on their own. But some resources store plain integers (Files + * and Buffers as of this writing), so we want to incorporate the 'kind' + * in the hash too, otherwise those resources will collide a lot. But + * because there are only a few resource kinds like that - and only a few + * resource kinds to begin with - we don't need to work too hard to mix + * 'kind' into the hash. Just add it with hash_combine(), it perturbs the + * result enough for our purposes. + */ +#if SIZEOF_DATUM == 8 + return hash_combine64(murmurhash64((uint64) value), (uint64) kind); +#else + return hash_combine(murmurhash32((uint32) value), (uint32) kind); +#endif } static void diff --git a/src/include/common/hashfn.h b/src/include/common/hashfn.h index c634cc067a1..009ffbbdd38 100644 --- a/src/include/common/hashfn.h +++ b/src/include/common/hashfn.h @@ -101,4 +101,19 @@ murmurhash32(uint32 data) return h; } +/* 64-bit variant */ +static inline uint64 +murmurhash64(uint64 data) +{ + uint64 h = data; + + h ^= h >> 33; + h *= 0xff51afd7ed558ccd; + h ^= h >> 33; + h *= 0xc4ceb9fe1a85ec53; + h ^= h >> 33; + + return h; +} + #endif /* HASHFN_H */ -- 2.29.2 --------------F30A5443A5D524A5CBC51AE7 Content-Type: text/x-patch; charset=UTF-8; name="v2-0001-resownerbench.patch" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="v2-0001-resownerbench.patch" ^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: Warning in geqo_main.c from clang 13 @ 2022-01-22 22:34 Tom Lane <[email protected]> 0 siblings, 0 replies; 2+ messages in thread From: Tom Lane @ 2022-01-22 22:34 UTC (permalink / raw) To: Thomas Munro <[email protected]>; +Cc: pgsql-hackers I wrote: > Thomas Munro <[email protected]> writes: >> Clang 13 on my machine and peripatus (but not Apple clang 13 on eg >> sifika, I'm still confused about Apple's versioning but I think that's >> really llvm 12-based) warns: >> geqo_main.c:86:8: warning: variable 'edge_failures' set but not used >> [-Wunused-but-set-variable] >> Here's one way to silence it. > I'm kind of inclined to just drop the edge_failures recording/logging > altogether, rather than make that rats-nest of #ifdefs even worse. > It's not like anyone has cared about that number in the last decade > or two. We're starting to see more buildfarm animals producing this warning, so I took another look, and thought of a slightly less invasive way to silence it. I confirmed this works with clang 13.0.0 on Fedora 35. regards, tom lane Attachments: [text/x-diff] silence-clang-warning-v2.patch (753B, ../../[email protected]/2-silence-clang-warning-v2.patch) download | inline diff: diff --git a/src/backend/optimizer/geqo/geqo_main.c b/src/backend/optimizer/geqo/geqo_main.c index 333a26a695..68ed74325c 100644 --- a/src/backend/optimizer/geqo/geqo_main.c +++ b/src/backend/optimizer/geqo/geqo_main.c @@ -227,12 +227,17 @@ geqo(PlannerInfo *root, int number_of_rels, List *initial_rels) } -#if defined(ERX) && defined(GEQO_DEBUG) +#if defined(ERX) +#if defined(GEQO_DEBUG) if (edge_failures != 0) elog(LOG, "[GEQO] failures: %d, average: %d", edge_failures, (int) number_generations / edge_failures); else elog(LOG, "[GEQO] no edge failures detected"); +#else + /* suppress variable-set-but-not-used warnings from some compilers */ + (void) edge_failures; +#endif #endif #if defined(CX) && defined(GEQO_DEBUG) ^ permalink raw reply [nested|flat] 2+ messages in thread
end of thread, other threads:[~2022-01-22 22:34 UTC | newest] Thread overview: 2+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2021-01-20 22:06 [PATCH v6 3/3] Optimize hash function Heikki Linnakangas <[email protected]> 2022-01-22 22:34 Re: Warning in geqo_main.c from clang 13 Tom Lane <[email protected]>
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