On Thu, 2024-06-20 at 17:07 +0700, John Naylor wrote:
> On Sat, Jun 15, 2024 at 6:46 AM Jeff Davis wrote:
> > Attached is a patch to use simplehash.h instead, which speeds
> > things up
> > enough to make them fairly close (from around 15% slower to around
> > 8%).
>
> +#define SH_HASH_KEY(tb, key) hash_uint32((uint32) key)
>
> For a static inline hash for speed reasons, we can use murmurhash32
> here, which is also inline.
Thank you, that brings it down a few more percentage points.
New patches attached, still based on the setlocale-removal patch
series.
Setup:
create collation libc_c (provider=libc, locale='C');
create table collation_cache_test(t text);
insert into collation_cache_test
select g::text||' '||g::text
from generate_series(1,2) g;
Queries:
select * from collation_cache_test where t < '0' collate "C";
select * from collation_cache_test where t < '0' collate libc_c;
The two collations are identical except that the former benefits from
the optimization for C_COLLATION_OID, and the latter does not, so these
queries measure the overhead of the collation cache lookup.
Results (in ms):
"C" "libc_c" overhead
master:6350 7855 24%
v4-0001: 6091 6324 4%
(Note: I don't have an explanation for the difference in performance of
the "C" locale -- probably just some noise in the test.)
Considering that simplehash brings the worst case overhead under 5%, I
don't see a big reason to use the single-element cache also.
Regards,
Jeff Davis
From 64a017f169858cf646002a28f97ae05cb7ab9fcd Mon Sep 17 00:00:00 2001
From: Jeff Davis
Date: Fri, 14 Jun 2024 15:38:42 -0700
Subject: [PATCH v4] Change collation cache to use simplehash.h.
---
src/backend/utils/adt/pg_locale.c | 39 +--
1 file changed, 27 insertions(+), 12 deletions(-)
diff --git a/src/backend/utils/adt/pg_locale.c b/src/backend/utils/adt/pg_locale.c
index 2e6f624798f..5afb69c6632 100644
--- a/src/backend/utils/adt/pg_locale.c
+++ b/src/backend/utils/adt/pg_locale.c
@@ -57,12 +57,12 @@
#include "access/htup_details.h"
#include "catalog/pg_collation.h"
#include "catalog/pg_database.h"
+#include "common/hashfn.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "utils/builtins.h"
#include "utils/formatting.h"
#include "utils/guc_hooks.h"
-#include "utils/hsearch.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/pg_locale.h"
@@ -129,10 +129,27 @@ typedef struct
{
Oid collid; /* hash key: pg_collation OID */
pg_locale_t locale; /* locale_t struct, or 0 if not valid */
-} collation_cache_entry;
-static HTAB *collation_cache = NULL;
+ /* needed for simplehash */
+ uint32 hash;
+ char status;
+} collation_cache_entry;
+#define SH_PREFIX collation_cache
+#define SH_ELEMENT_TYPE collation_cache_entry
+#define SH_KEY_TYPE Oid
+#define SH_KEY collid
+#define SH_HASH_KEY(tb, key) murmurhash32((uint32) key)
+#define SH_EQUAL(tb, a, b) (a == b)
+#define SH_GET_HASH(tb, a) a->hash
+#define SH_SCOPE static inline
+#define SH_STORE_HASH
+#define SH_DECLARE
+#define SH_DEFINE
+#include "lib/simplehash.h"
+
+static MemoryContext CollationCacheContext = NULL;
+static collation_cache_hash *CollationCache = NULL;
#if defined(WIN32) && defined(LC_MESSAGES)
static char *IsoLocaleName(const char *);
@@ -1219,18 +1236,16 @@ lookup_collation_cache(Oid collation)
Assert(OidIsValid(collation));
Assert(collation != DEFAULT_COLLATION_OID);
- if (collation_cache == NULL)
+ if (CollationCache == NULL)
{
- /* First time through, initialize the hash table */
- HASHCTL ctl;
-
- ctl.keysize = sizeof(Oid);
- ctl.entrysize = sizeof(collation_cache_entry);
- collation_cache = hash_create("Collation cache", 100, ,
- HASH_ELEM | HASH_BLOBS);
+ CollationCacheContext = AllocSetContextCreate(TopMemoryContext,
+ "collation cache",
+ ALLOCSET_DEFAULT_SIZES);
+ CollationCache = collation_cache_create(
+ CollationCacheContext, 16, NULL);
}
- cache_entry = hash_search(collation_cache, , HASH_ENTER, );
+ cache_entry = collation_cache_insert(CollationCache, collation, );
if (!found)
{
/*
--
2.34.1
