From ac998020802b742303979a13692afa7b2084d0e9 Mon Sep 17 00:00:00 2001 From: David Rowley Date: Fri, 16 Dec 2022 10:31:25 +1300 Subject: [PATCH] Speed up creation of command completion tags The building of command completion tags could often be seen showing up in profiles when running high tps workloads. The query completion tags were being built with snprintf, which is slow at the best of times when compared with more manual ways of formatting strings. Here we introduce BuildQueryCompletionString() to do this job for us. We also now store the completion tag's strlen in the CommandTagBehavior struct so that we can quickly memcpy this number of bytes into the completion tag string. Appending the rows affected is done via pg_ulltoa_n. BuildQueryCompletionString returns the length of the built string. This saves us having to call strlen to figure out how many bytes to pass to pq_putmessage(). Author: David Rowley, Andres Freund Reviewed-by: Andres Freund Discussion: https://postgr.es/m/CAHoyFK-Xwqc-iY52shj0G+8K9FJpse+FuZ36XBKy78wDVnd=Qg@mail.gmail.com --- src/backend/tcop/cmdtag.c | 72 +++++++++++++++++++++++++++++++++++++-- src/backend/tcop/dest.c | 29 +++------------- src/include/tcop/cmdtag.h | 5 +++ src/include/tcop/dest.h | 2 -- 4 files changed, 78 insertions(+), 30 deletions(-) diff --git a/src/backend/tcop/cmdtag.c b/src/backend/tcop/cmdtag.c index 262484f561..2970f680eb 100644 --- a/src/backend/tcop/cmdtag.c +++ b/src/backend/tcop/cmdtag.c @@ -15,18 +15,21 @@ #include "miscadmin.h" #include "tcop/cmdtag.h" +#include "utils/builtins.h" typedef struct CommandTagBehavior { - const char *name; + const char *name; /* tag name, e.g. "SELECT" */ + const uint8 namelen; /* set to strlen(name) */ const bool event_trigger_ok; const bool table_rewrite_ok; - const bool display_rowcount; + const bool display_rowcount; /* should the number of rows affected be + * shown in the command completion string */ } CommandTagBehavior; #define PG_CMDTAG(tag, name, evtrgok, rwrok, rowcnt) \ - { name, evtrgok, rwrok, rowcnt }, + { name, (uint8) (sizeof(name) - 1), evtrgok, rwrok, rowcnt }, static const CommandTagBehavior tag_behavior[COMMAND_TAG_NEXTTAG] = { #include "tcop/cmdtaglist.h" @@ -47,6 +50,13 @@ GetCommandTagName(CommandTag commandTag) return tag_behavior[commandTag].name; } +const char * +GetCommandTagNameAndLen(CommandTag commandTag, Size *len) +{ + *len = (Size) tag_behavior[commandTag].namelen; + return tag_behavior[commandTag].name; +} + bool command_tag_display_rowcount(CommandTag commandTag) { @@ -96,3 +106,59 @@ GetCommandTagEnum(const char *commandname) } return CMDTAG_UNKNOWN; } + +/* + * BuildQueryCompletionString + * Build a string containing the command tag name with the + * QueryCompletion's nprocessed for command tags with display_rowcount + * set. Returns the strlen of the constructed string. + * + * The caller must ensure that buff is at least COMPLETION_TAG_BUFSIZE bytes. + * + * If nameonly is true, then the constructed string will contain only the tag + * name. + */ +Size +BuildQueryCompletionString(char *buff, const QueryCompletion *qc, + bool nameonly) +{ + CommandTag tag = qc->commandTag; + Size taglen; + const char *tagname = GetCommandTagNameAndLen(tag, &taglen); + char *bufp; + + /* + * We assume the tagname is plain ASCII and therefore requires no encoding + * conversion. + */ + memcpy(buff, tagname, taglen); + bufp = buff + taglen; + + /* ensure that the tagname isn't long enough to overrun the buffer */ + Assert(taglen <= COMPLETION_TAG_BUFSIZE - MAXINT8LEN - 4); + + /* + * In PostgreSQL versions 11 and earlier, it was possible to create a + * table WITH OIDS. When inserting into such a table, INSERT used to + * include the Oid of the inserted record in the completion tag. To + * maintain compatibility in the wire protocol, we now write a "0" (for + * InvalidOid) in the location where we once wrote the new record's Oid. + */ + if (command_tag_display_rowcount(tag) && !nameonly) + { + if (tag == CMDTAG_INSERT) + { + *bufp++ = ' '; + *bufp++ = '0'; + } + *bufp++ = ' '; + bufp += pg_ulltoa_n(qc->nprocessed, bufp); + } + + /* and finally, NUL terminate the string */ + *bufp = '\0'; + + Assert((bufp - buff) == strlen(buff)); + + return bufp - buff; +} diff --git a/src/backend/tcop/dest.c b/src/backend/tcop/dest.c index 6afaa153ca..e879304ae1 100644 --- a/src/backend/tcop/dest.c +++ b/src/backend/tcop/dest.c @@ -166,8 +166,7 @@ void EndCommand(const QueryCompletion *qc, CommandDest dest, bool force_undecorated_output) { char completionTag[COMPLETION_TAG_BUFSIZE]; - CommandTag tag; - const char *tagname; + Size len; switch (dest) { @@ -175,29 +174,9 @@ EndCommand(const QueryCompletion *qc, CommandDest dest, bool force_undecorated_o case DestRemoteExecute: case DestRemoteSimple: - /* - * We assume the tagname is plain ASCII and therefore requires no - * encoding conversion. - */ - tag = qc->commandTag; - tagname = GetCommandTagName(tag); - - /* - * In PostgreSQL versions 11 and earlier, it was possible to - * create a table WITH OIDS. When inserting into such a table, - * INSERT used to include the Oid of the inserted record in the - * completion tag. To maintain compatibility in the wire - * protocol, we now write a "0" (for InvalidOid) in the location - * where we once wrote the new record's Oid. - */ - if (command_tag_display_rowcount(tag) && !force_undecorated_output) - snprintf(completionTag, COMPLETION_TAG_BUFSIZE, - tag == CMDTAG_INSERT ? - "%s 0 " UINT64_FORMAT : "%s " UINT64_FORMAT, - tagname, qc->nprocessed); - else - snprintf(completionTag, COMPLETION_TAG_BUFSIZE, "%s", tagname); - pq_putmessage('C', completionTag, strlen(completionTag) + 1); + len = BuildQueryCompletionString(completionTag, qc, + force_undecorated_output); + pq_putmessage('C', completionTag, len + 1); case DestNone: case DestDebug: diff --git a/src/include/tcop/cmdtag.h b/src/include/tcop/cmdtag.h index 60e3179c74..9bde568bb0 100644 --- a/src/include/tcop/cmdtag.h +++ b/src/include/tcop/cmdtag.h @@ -13,6 +13,8 @@ #ifndef CMDTAG_H #define CMDTAG_H +/* buffer size required for command completion tags */ +#define COMPLETION_TAG_BUFSIZE 64 #define PG_CMDTAG(tag, name, evtrgok, rwrok, rowcnt) \ tag, @@ -50,9 +52,12 @@ CopyQueryCompletion(QueryCompletion *dst, const QueryCompletion *src) extern void InitializeQueryCompletion(QueryCompletion *qc); extern const char *GetCommandTagName(CommandTag commandTag); +extern const char *GetCommandTagNameAndLen(CommandTag commandTag, Size *len); extern bool command_tag_display_rowcount(CommandTag commandTag); extern bool command_tag_event_trigger_ok(CommandTag commandTag); extern bool command_tag_table_rewrite_ok(CommandTag commandTag); extern CommandTag GetCommandTagEnum(const char *commandname); +extern Size BuildQueryCompletionString(char *buff, const QueryCompletion *qc, + bool nameonly); #endif /* CMDTAG_H */ diff --git a/src/include/tcop/dest.h b/src/include/tcop/dest.h index 3c3eabae67..83d1af88b4 100644 --- a/src/include/tcop/dest.h +++ b/src/include/tcop/dest.h @@ -71,8 +71,6 @@ #include "tcop/cmdtag.h" -/* buffer size to use for command completion tags */ -#define COMPLETION_TAG_BUFSIZE 64 /* ----------------