rdelaage
/
postgresql
mirror of https://git.postgresql.org/git/postgresql.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Add auto-explain contrib module for automatic logging of the plans of 

slow-running queries.

Takahiro Itagaki
This commit is contained in:
Tom Lane 2008-11-19 02:59:28 +00:00
parent 31ec957a15
commit e125e28e78
7 changed files with 429 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
contrib/Makefile
View File

@ -1,4 +1,4 @@
# $PostgreSQL: pgsql/contrib/Makefile,v 1.84 2008/07/29 18:31:20 tgl Exp $
# $PostgreSQL: pgsql/contrib/Makefile,v 1.85 2008/11/19 02:59:28 tgl Exp $
subdir = contrib
top_builddir = ..
@ -6,6 +6,7 @@ include $(top_builddir)/src/Makefile.global
WANTED_DIRS = \
adminpack \
auto_explain \
btree_gist \
chkpass \
citext \

4
contrib/README
View File

@ -28,6 +28,10 @@ adminpack -
File and log manipulation routines, used by pgAdmin
by Dave Page <dpage@vale-housing.co.uk>
auto_explain -
Log EXPLAIN output for long-running queries
by Takahiro Itagaki <itagaki.takahiro@oss.ntt.co.jp>
btree_gist -
Support for emulating BTREE indexing in GiST
by Oleg Bartunov <oleg@sai.msu.su> and Teodor Sigaev <teodor@sigaev.ru>

15
contrib/auto_explain/Makefile Normal file
View File

@ -0,0 +1,15 @@
# $PostgreSQL: pgsql/contrib/auto_explain/Makefile,v 1.1 2008/11/19 02:59:28 tgl Exp $
MODULE_big = auto_explain
OBJS = auto_explain.o
ifdef USE_PGXS
PG_CONFIG = pg_config
PGXS := $(shell $(PG_CONFIG) --pgxs)
include $(PGXS)
else
subdir = contrib/auto_explain
top_builddir = ../..
include $(top_builddir)/src/Makefile.global
include $(top_srcdir)/contrib/contrib-global.mk
endif

228
contrib/auto_explain/auto_explain.c Normal file
View File

@ -0,0 +1,228 @@
/*-------------------------------------------------------------------------
*
* auto_explain.c
*
*
* Copyright (c) 2008, PostgreSQL Global Development Group
*
* IDENTIFICATION
* $PostgreSQL: pgsql/contrib/auto_explain/auto_explain.c,v 1.1 2008/11/19 02:59:28 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "commands/explain.h"
#include "executor/instrument.h"
#include "utils/guc.h"
PG_MODULE_MAGIC;
#define GUCNAME(name) ("explain." name)
/* GUC variables */
static int explain_log_min_duration = -1; /* msec or -1 */
static bool explain_log_analyze = false;
static bool explain_log_verbose = false;
static bool explain_log_nested = false;
/* Current nesting depth of ExecutorRun calls */
static int nesting_level = 0;
/* Saved hook values in case of unload */
static ExecutorStart_hook_type prev_ExecutorStart = NULL;
static ExecutorRun_hook_type prev_ExecutorRun = NULL;
static ExecutorEnd_hook_type prev_ExecutorEnd = NULL;
#define auto_explain_enabled() \
(explain_log_min_duration >= 0 && \
(nesting_level == 0 || explain_log_nested))
void _PG_init(void);
void _PG_fini(void);
static void explain_ExecutorStart(QueryDesc *queryDesc, int eflags);
static void explain_ExecutorRun(QueryDesc *queryDesc,
ScanDirection direction,
long count);
static void explain_ExecutorEnd(QueryDesc *queryDesc);
/*
* Module load callback
*/
void
_PG_init(void)
{
/* Define custom GUC variables. */
DefineCustomIntVariable(GUCNAME("log_min_duration"),
"Sets the minimum execution time above which plans will be logged.",
"Zero prints all plans. -1 turns this feature off.",
&explain_log_min_duration,
-1,
-1, INT_MAX / 1000,
PGC_SUSET,
GUC_UNIT_MS,
NULL,
NULL);
DefineCustomBoolVariable(GUCNAME("log_analyze"),
"Use EXPLAIN ANALYZE for plan logging.",
NULL,
&explain_log_analyze,
false,
PGC_SUSET,
0,
NULL,
NULL);
DefineCustomBoolVariable(GUCNAME("log_verbose"),
"Use EXPLAIN VERBOSE for plan logging.",
NULL,
&explain_log_verbose,
false,
PGC_SUSET,
0,
NULL,
NULL);
DefineCustomBoolVariable(GUCNAME("log_nested_statements"),
"Log nested statements.",
NULL,
&explain_log_nested,
false,
PGC_SUSET,
0,
NULL,
NULL);
/* Install hooks. */
prev_ExecutorStart = ExecutorStart_hook;
ExecutorStart_hook = explain_ExecutorStart;
prev_ExecutorRun = ExecutorRun_hook;
ExecutorRun_hook = explain_ExecutorRun;
prev_ExecutorEnd = ExecutorEnd_hook;
ExecutorEnd_hook = explain_ExecutorEnd;
}
/*
* Module unload callback
*/
void
_PG_fini(void)
{
/* Uninstall hooks. */
ExecutorStart_hook = prev_ExecutorStart;
ExecutorRun_hook = prev_ExecutorRun;
ExecutorEnd_hook = prev_ExecutorEnd;
}
/*
* ExecutorStart hook: start up logging if needed
*/
void
explain_ExecutorStart(QueryDesc *queryDesc, int eflags)
{
if (auto_explain_enabled())
{
/* Enable per-node instrumentation iff log_analyze is required. */
if (explain_log_analyze && (eflags & EXEC_FLAG_EXPLAIN_ONLY) == 0)
queryDesc->doInstrument = true;
}
if (prev_ExecutorStart)
prev_ExecutorStart(queryDesc, eflags);
else
standard_ExecutorStart(queryDesc, eflags);
if (auto_explain_enabled())
{
/*
* Set up to track total elapsed time in ExecutorRun. Make sure
* the space is allocated in the per-query context so it will go
* away at ExecutorEnd.
*/
if (queryDesc->totaltime == NULL)
{
MemoryContext oldcxt;
oldcxt = MemoryContextSwitchTo(queryDesc->estate->es_query_cxt);
queryDesc->totaltime = InstrAlloc(1);
MemoryContextSwitchTo(oldcxt);
}
}
}
/*
* ExecutorRun hook: all we need do is track nesting depth
*/
void
explain_ExecutorRun(QueryDesc *queryDesc, ScanDirection direction, long count)
{
nesting_level++;
PG_TRY();
{
if (prev_ExecutorRun)
prev_ExecutorRun(queryDesc, direction, count);
else
standard_ExecutorRun(queryDesc, direction, count);
nesting_level--;
}
PG_CATCH();
{
nesting_level--;
PG_RE_THROW();
}
PG_END_TRY();
}
/*
* ExecutorEnd hook: log results if needed
*/
void
explain_ExecutorEnd(QueryDesc *queryDesc)
{
if (queryDesc->totaltime && auto_explain_enabled())
{
double msec;
/*
* Make sure stats accumulation is done. (Note: it's okay if
* several levels of hook all do this.)
*/
InstrEndLoop(queryDesc->totaltime);
/* Log plan if duration is exceeded. */
msec = queryDesc->totaltime->total * 1000.0;
if (msec >= explain_log_min_duration)
{
StringInfoData buf;
initStringInfo(&buf);
ExplainPrintPlan(&buf, queryDesc,
queryDesc->doInstrument && explain_log_analyze,
explain_log_verbose);
/* Remove last line break */
if (buf.len > 0 && buf.data[buf.len - 1] == '\n')
buf.data[--buf.len] = '\0';
/*
* Note: we rely on the existing logging of context or
* debug_query_string to identify just which statement is being
* reported. This isn't ideal but trying to do it here would
* often result in duplication.
*/
ereport(LOG,
(errmsg("duration: %.3f ms plan:\n%s",
msec, buf.data)));
pfree(buf.data);
}
}
if (prev_ExecutorEnd)
prev_ExecutorEnd(queryDesc);
else
standard_ExecutorEnd(queryDesc);
}

176
doc/src/sgml/auto-explain.sgml Normal file
View File

@ -0,0 +1,176 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/auto-explain.sgml,v 1.1 2008/11/19 02:59:28 tgl Exp $ -->
<sect1 id="auto-explain">
<title>auto_explain</title>
<indexterm zone="auto-explain">
<primary>auto_explain</primary>
</indexterm>
<para>
The <filename>auto_explain</filename> module provides a means for
logging execution plans of slow statements automatically, without
having to run <xref linkend="sql-explain" endterm="sql-explain-title">
by hand. This is especially helpful for tracking down un-optimized queries
in large applications.
</para>
<para>
The module provides no SQL-accessible functions. To use it, simply
load it into the server. You can load it into an individual session:
<programlisting>
LOAD 'auto_explain';
</programlisting>
(You must be superuser to do that.) More typical usage is to preload
it into all sessions by including <literal>auto_explain</> in
<xref linkend="guc-shared-preload-libraries"> in
<filename>postgresql.conf</>. Then you can track unexpectedly slow queries
no matter when they happen. Of course there is a price in overhead for
that.
</para>
<sect2>
<title>Configuration parameters</title>
<para>
There are several configuration parameters that control the behavior of
<filename>auto_explain</filename>. Note that the default behavior is
to do nothing, so you must set at least
<varname>explain.log_min_duration</varname> if you want any results.
</para>
<variablelist>
<varlistentry>
<term>
<varname>explain.log_min_duration</varname> (<type>integer</type>)
</term>
<indexterm>
<primary><varname>explain.log_min_duration</> configuration parameter</primary>
</indexterm>
<listitem>
<para>
<varname>explain.log_min_duration</varname> is the minimum statement
execution time, in milliseconds, that will cause the statement's plan to
be logged. Setting this to zero logs all plans. Minus-one (the default)
disables logging of plans. For example, if you set it to
<literal>250ms</literal> then all statements that run 250ms or longer
will be logged. Only superusers can change this setting.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<varname>explain.log_analyze</varname> (<type>boolean</type>)
</term>
<indexterm>
<primary><varname>explain.log_analyze</> configuration parameter</primary>
</indexterm>
<listitem>
<para>
<varname>explain.log_analyze</varname> causes <command>EXPLAIN ANALYZE</>
output, rather than just <command>EXPLAIN</> output, to be printed
when an execution plan is logged. This parameter is off by default.
Only superusers can change this setting.
</para>
<note>
<para>
When this parameter is on, per-plan-node timing occurs for all
statements executed, whether or not they run long enough to actually
get logged. This can have extremely negative impact on performance.
</para>
</note>
</listitem>
</varlistentry>
<varlistentry>
<term>
<varname>explain.log_verbose</varname> (<type>boolean</type>)
</term>
<indexterm>
<primary><varname>explain.log_verbose</> configuration parameter</primary>
</indexterm>
<listitem>
<para>
<varname>explain.log_verbose</varname> causes <command>EXPLAIN VERBOSE</>
output, rather than just <command>EXPLAIN</> output, to be printed
when an execution plan is logged. This parameter is off by default.
Only superusers can change this setting.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<varname>explain.log_nested_statements</varname> (<type>boolean</type>)
</term>
<indexterm>
<primary><varname>explain.log_nested_statements</> configuration parameter</primary>
</indexterm>
<listitem>
<para>
<varname>explain.log_nested_statements</varname> causes nested
statements (statements executed inside a function) to be considered
for logging. When it is off, only top-level query plans are logged. This
parameter is off by default. Only superusers can change this setting.
</para>
</listitem>
</varlistentry>
</variablelist>
<para>
In order to set these parameters in your <filename>postgresql.conf</> file,
you will need to add <literal>explain</> in
<varname>custom_variable_classes</>. Typical usage might be:
</para>
<programlisting>
# postgresql.conf
shared_preload_libraries = 'auto_explain'
custom_variable_classes = 'explain'
explain.log_min_duration = '3s'
</programlisting>
</sect2>
<sect2>
<title>Example</title>
<programlisting>
postgres=# LOAD 'auto_explain';
postgres=# SET explain.log_min_duration = 0;
postgres=# SELECT count(*)
FROM pg_class, pg_index
WHERE oid = indrelid AND indisunique;
</programlisting>
<para>
This might produce log output such as:
</para>
<programlisting>
LOG: duration: 0.986 ms plan:
Aggregate (cost=14.90..14.91 rows=1 width=0)
-&gt; Hash Join (cost=3.91..14.70 rows=81 width=0)
Hash Cond: (pg_class.oid = pg_index.indrelid)
-&gt; Seq Scan on pg_class (cost=0.00..8.27 rows=227 width=4)
-&gt; Hash (cost=2.90..2.90 rows=81 width=4)
-&gt; Seq Scan on pg_index (cost=0.00..2.90 rows=81 width=4)
Filter: indisunique
STATEMENT: SELECT count(*)
FROM pg_class, pg_index
WHERE oid = indrelid AND indisunique;
</programlisting>
</sect2>
<sect2>
<title>Author</title>
<para>
Takahiro Itagaki <email>itagaki.takahiro@oss.ntt.co.jp</email>
</para>
</sect2>
</sect1>

3
doc/src/sgml/contrib.sgml
View File

@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/contrib.sgml,v 1.9 2008/07/29 18:31:20 tgl Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/contrib.sgml,v 1.10 2008/11/19 02:59:28 tgl Exp $ -->
<appendix id="contrib">
<title>Additional Supplied Modules</title>
@ -79,6 +79,7 @@ psql -d dbname -f <replaceable>SHAREDIR</>/contrib/<replaceable>module</>.sql
</para>
&adminpack;
&auto-explain;
&btree-gist;
&chkpass;
&citext;

3
doc/src/sgml/filelist.sgml
View File

@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/filelist.sgml,v 1.57 2008/07/29 18:31:20 tgl Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/filelist.sgml,v 1.58 2008/11/19 02:59:28 tgl Exp $ -->
<!entity history SYSTEM "history.sgml">
<!entity info SYSTEM "info.sgml">
@ -92,6 +92,7 @@
<!-- contrib information -->
<!entity contrib SYSTEM "contrib.sgml">
<!entity adminpack SYSTEM "adminpack.sgml">
<!entity auto-explain SYSTEM "auto-explain.sgml">
<!entity btree-gist SYSTEM "btree-gist.sgml">
<!entity chkpass SYSTEM "chkpass.sgml">
<!entity citext SYSTEM "citext.sgml">