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Speed up uuid_out() by not relying on a StringInfo

author Michael Paquier <michael@paquier.xyz>

2024年2月22日 01:02:55 +0000 (10:02 +0900)

committer Michael Paquier <michael@paquier.xyz>

2024年2月22日 01:02:55 +0000 (10:02 +0900)

Since the size of the string representation of an uuid is fixed, there
is no benefit in using a StringInfo. This commit simplifies uuid_oud()
to not rely on a StringInfo, where avoiding the overhead of the string
manipulation makes the function substantially faster.

A COPY TO on a relation with one UUID attribute can show up to a 40%
speedup when the bottleneck is the COPY computation with uuid_out()
showing up at the top of the profiles (numbered measure here, Laurenz
has mentioned something closer to 20% faster runtimes), for example when
the data is fully in shared buffers or the OS cache.

Author: Laurenz Albe
Reviewed-by: Andres Freund, Michael Paquier
Description: https://postgr.es/m/679d5455cbbb0af667ccb753da51a475bae1eaed.camel@cybertec.at

src/backend/utils/adt/uuid.c patch | blob | blame | history

diff --git a/src/backend/utils/adt/uuid.c b/src/backend/utils/adt/uuid.c

index 73dfd711c7311d8de69172a81292a23d18c9ba5b..2ca8fc6994300030db06204c8f9fe572128484bf 100644 (file)

--- a/src/backend/utils/adt/uuid.c

+++ b/src/backend/utils/adt/uuid.c

@@ -53,10 +53,13 @@ uuid_out(PG_FUNCTION_ARGS)

{

pg_uuid_t *uuid = PG_GETARG_UUID_P(0);

static const char hex_chars[] = "0123456789abcdef";

- StringInfoData buf;

+ char *buf,

+ *p;

int i;

- initStringInfo(&buf);

+ /* counts for the four hyphens and the zero-terminator */

+ buf = palloc(2 * UUID_LEN + 5);

+ p = buf;

for (i = 0; i < UUID_LEN; i++)

{

int hi;

@@ -68,16 +71,17 @@ uuid_out(PG_FUNCTION_ARGS)

* ("-"). Therefore, add the hyphens at the appropriate places here.

if (i == 4 || i == 6 || i == 8 || i == 10)

- appendStringInfoChar(&buf, '-');

+ *p++ = '-';

hi = uuid->data[i] >> 4;

lo = uuid->data[i] & 0x0F;

- appendStringInfoChar(&buf, hex_chars[hi]);

- appendStringInfoChar(&buf, hex_chars[lo]);

+ *p++ = hex_chars[hi];

+ *p++ = hex_chars[lo];

}

+ *p = '0円';

- PG_RETURN_CSTRING(buf.data);

+ PG_RETURN_CSTRING(buf);

}

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