From 5ff8c2d7d60d0084f577a920c9d614221bde283a Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Fri, 19 Sep 2014 13:19:05 -0400
Subject: [PATCH] Fix failure of contrib/auto_explain to print per-node timing
information.
This has been broken since commit af7914c6627bcf0b0ca614e9ce95d3f8056602bf,
which added the EXPLAIN (TIMING) option. Although that commit included
updates to auto_explain, they evidently weren't tested very carefully,
because the code failed to print node timings even when it should, due to
failure to set es.timing in the ExplainState struct. Reported off-list by
Neelakanth Nadgir of Salesforce.
In passing, clean up the documentation for auto_explain's options a
little bit, including re-ordering them into what seems to me a more
logical order.
---
contrib/auto_explain/auto_explain.c | 5 +-
doc/src/sgml/auto-explain.sgml | 72 ++++++++++++++++-------------
2 files changed, 43 insertions(+), 34 deletions(-)
diff --git a/contrib/auto_explain/auto_explain.c b/contrib/auto_explain/auto_explain.c
index ad333b66447..63fc311835a 100644
--- a/contrib/auto_explain/auto_explain.c
+++ b/contrib/auto_explain/auto_explain.c
@@ -23,7 +23,7 @@ static int auto_explain_log_min_duration = -1; /* msec or -1 */
static bool auto_explain_log_analyze = false;
static bool auto_explain_log_verbose = false;
static bool auto_explain_log_buffers = false;
-static bool auto_explain_log_timing = false;
+static bool auto_explain_log_timing = true;
static int auto_explain_log_format = EXPLAIN_FORMAT_TEXT;
static bool auto_explain_log_nested_statements = false;
@@ -186,8 +186,6 @@ explain_ExecutorStart(QueryDesc *queryDesc, int eflags)
queryDesc->instrument_options |= INSTRUMENT_TIMER;
else
queryDesc->instrument_options |= INSTRUMENT_ROWS;
-
-
if (auto_explain_log_buffers)
queryDesc->instrument_options |= INSTRUMENT_BUFFERS;
}
@@ -288,6 +286,7 @@ explain_ExecutorEnd(QueryDesc *queryDesc)
es.analyze = (queryDesc->instrument_options && auto_explain_log_analyze);
es.verbose = auto_explain_log_verbose;
es.buffers = (es.analyze && auto_explain_log_buffers);
+ es.timing = (es.analyze && auto_explain_log_timing);
es.format = auto_explain_log_format;
ExplainBeginOutput(&es);
diff --git a/doc/src/sgml/auto-explain.sgml b/doc/src/sgml/auto-explain.sgml
index 03b2309da8f..910cce1bd28 100644
--- a/doc/src/sgml/auto-explain.sgml
+++ b/doc/src/sgml/auto-explain.sgml
@@ -80,6 +80,8 @@ LOAD 'auto_explain';
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 an extremely negative impact on performance.
+ Turning off <varname>auto_explain.log_timing</varname> ameliorates the
+ performance cost, at the price of obtaining less information.
</para>
</note>
</listitem>
@@ -87,16 +89,19 @@ LOAD 'auto_explain';
<varlistentry>
<term>
- <varname>auto_explain.log_verbose</varname> (<type>boolean</type>)
+ <varname>auto_explain.log_buffers</varname> (<type>boolean</type>)
</term>
<indexterm>
- <primary><varname>auto_explain.log_verbose</> configuration parameter</primary>
+ <primary><varname>auto_explain.log_buffers</> configuration parameter</primary>
</indexterm>
<listitem>
<para>
- <varname>auto_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.
+ <varname>auto_explain.log_buffers</varname> controls whether buffer
+ usage statistics are printed when an execution plan is logged; it's
+ equivalent to the <literal>BUFFERS</> option of <command>EXPLAIN</>.
+ This parameter has no effect
+ unless <varname>auto_explain.log_analyze</varname> is enabled.
+ This parameter is off by default.
Only superusers can change this setting.
</para>
</listitem>
@@ -104,36 +109,41 @@ LOAD 'auto_explain';
<varlistentry>
<term>
- <varname>auto_explain.log_buffers</varname> (<type>boolean</type>)
+ <varname>auto_explain.log_timing</varname> (<type>boolean</type>)
</term>
<indexterm>
- <primary><varname>auto_explain.log_buffers</> configuration parameter</primary>
+ <primary><varname>auto_explain.log_timing</> configuration parameter</primary>
</indexterm>
<listitem>
<para>
- <varname>auto_explain.log_buffers</varname> causes <command>EXPLAIN
- (ANALYZE, BUFFERS)</> 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. This
- parameter has no effect unless <varname>auto_explain.log_analyze</>
- parameter is set.
+ <varname>auto_explain.log_timing</varname> controls whether per-node
+ timing information is printed when an execution plan is logged; it's
+ equivalent to the <literal>TIMING</> option of <command>EXPLAIN</>.
+ The overhead of repeatedly reading the system clock can slow down
+ queries significantly on some systems, so it may be useful to set this
+ parameter to off when only actual row counts, and not exact times, are
+ needed.
+ This parameter has no effect
+ unless <varname>auto_explain.log_analyze</varname> is enabled.
+ This parameter is on by default.
+ Only superusers can change this setting.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
- <varname>auto_explain.log_format</varname> (<type>enum</type>)
+ <varname>auto_explain.log_verbose</varname> (<type>boolean</type>)
</term>
<indexterm>
- <primary><varname>auto_explain.log_format</> configuration parameter</primary>
+ <primary><varname>auto_explain.log_verbose</> configuration parameter</primary>
</indexterm>
<listitem>
<para>
- <varname>auto_explain.log_format</varname> selects the
- <command>EXPLAIN</> output format to be used.
- The allowed values are <literal>text</literal>, <literal>xml</literal>,
- <literal>json</literal>, and <literal>yaml</literal>. The default is text.
+ <varname>auto_explain.log_verbose</varname> controls whether verbose
+ details are printed when an execution plan is logged; it's
+ equivalent to the <literal>VERBOSE</> option of <command>EXPLAIN</>.
+ This parameter is off by default.
Only superusers can change this setting.
</para>
</listitem>
@@ -141,25 +151,22 @@ LOAD 'auto_explain';
<varlistentry>
<term>
- <varname>auto_explain.log_timing</varname> (<type>boolean</type>)
+ <varname>auto_explain.log_format</varname> (<type>enum</type>)
</term>
<indexterm>
- <primary><varname>auto_explain.log_timing</> configuration parameter</primary>
+ <primary><varname>auto_explain.log_format</> configuration parameter</primary>
</indexterm>
<listitem>
<para>
- <varname>auto_explain.log_timing</varname> causes <command>EXPLAIN
- (ANALYZE, TIMING off)</> output, rather than just <command>EXPLAIN (ANALYZE)</>
- output. The overhead of repeatedly reading the system clock can slow down the
- query significantly on some systems, so it may be useful to set this
- parameter to <literal>FALSE</literal> when only actual row counts, and not
- exact times, are needed.
- This parameter is only effective when <varname>auto_explain.log_analyze</varname>
- is also enabled. It defaults to <literal>TRUE</literal>.
+ <varname>auto_explain.log_format</varname> selects the
+ <command>EXPLAIN</> output format to be used.
+ The allowed values are <literal>text</literal>, <literal>xml</literal>,
+ <literal>json</literal>, and <literal>yaml</literal>. The default is text.
+ Only superusers can change this setting.
</para>
</listitem>
</varlistentry>
-
+
<varlistentry>
<term>
<varname>auto_explain.log_nested_statements</varname> (<type>boolean</type>)
@@ -179,7 +186,9 @@ LOAD 'auto_explain';
</variablelist>
<para>
- These parameters must be set in <filename>postgresql.conf</>.
+ In ordinary usage, these parameters are set
+ in <filename>postgresql.conf</>, although superusers can alter them
+ on-the-fly within their own sessions.
Typical usage might be:
</para>
@@ -197,6 +206,7 @@ auto_explain.log_min_duration = '3s'
<programlisting>
postgres=# LOAD 'auto_explain';
postgres=# SET auto_explain.log_min_duration = 0;
+postgres=# SET auto_explain.log_analyze = true;
postgres=# SELECT count(*)
FROM pg_class, pg_index
WHERE oid = indrelid AND indisunique;
--
GitLab