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Commit954e435

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Use a faster hash function in resource owners.
This buys back some of the performance loss that we otherwise saw from theprevious commit.Reviewed-by: Aleksander Alekseev, Michael Paquier, Julien RouhaudReviewed-by: Kyotaro Horiguchi, Hayato Kuroda, Álvaro Herrera, Zhihong YuReviewed-by: Peter Eisentraut, Andres FreundDiscussion:https://www.postgresql.org/message-id/d746cead-a1ef-7efe-fb47-933311e876a3%40iki.fi
1 parentb8bff07 commit954e435

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2 files changed

+33
-6
lines changed

2 files changed

+33
-6
lines changed

‎src/backend/utils/resowner/resowner.c

Lines changed: 18 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -206,15 +206,27 @@ static void ReleaseAuxProcessResourcesCallback(int code, Datum arg);
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* INTERNAL ROUTINES *
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*****************************************************************************/
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/*
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* Hash function for value+kind combination.
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*/
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staticinlineuint32
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hash_resource_elem(Datumvalue,constResourceOwnerDesc*kind)
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{
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Datumdata[2];
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data[0]=value;
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data[1]=PointerGetDatum(kind);
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returnhash_bytes((unsignedchar*)&data,2*SIZEOF_DATUM);
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/*
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* Most resource kinds store a pointer in 'value', and pointers are unique
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* all on their own. But some resources store plain integers (Files and
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* Buffers as of this writing), so we want to incorporate the 'kind' in
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* the hash too, otherwise those resources will collide a lot. But
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* because there are only a few resource kinds like that - and only a few
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* resource kinds to begin with - we don't need to work too hard to mix
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* 'kind' into the hash. Just add it with hash_combine(), it perturbs the
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* result enough for our purposes.
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*/
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#ifSIZEOF_DATUM==8
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returnhash_combine64(murmurhash64((uint64)value), (uint64)kind);
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#else
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returnhash_combine(murmurhash32((uint32)value), (uint32)kind);
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#endif
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}
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/*

‎src/include/common/hashfn.h

Lines changed: 15 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -101,4 +101,19 @@ murmurhash32(uint32 data)
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returnh;
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}
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/* 64-bit variant */
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staticinlineuint64
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murmurhash64(uint64data)
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{
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uint64h=data;
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h ^=h >>33;
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h *=0xff51afd7ed558ccd;
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h ^=h >>33;
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h *=0xc4ceb9fe1a85ec53;
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h ^=h >>33;
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returnh;
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}
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#endif/* HASHFN_H */

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