From 011d60c4352c5c48c0f1a185e8a12833c22a58db Mon Sep 17 00:00:00 2001 From: Michael Paquier Date: Thu, 22 Feb 2024 10:02:55 +0900 Subject: [PATCH] Speed up uuid_out() by not relying on a StringInfo 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 | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) diff --git a/src/backend/utils/adt/uuid.c b/src/backend/utils/adt/uuid.c index 73dfd711c73..2ca8fc69943 100644 --- 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'; - PG_RETURN_CSTRING(buf.data); + PG_RETURN_CSTRING(buf); } /*