From 898f8a96ef9dfa79eac9ec1621a89e71fe16601c Mon Sep 17 00:00:00 2001
From: Tom Lane
Date: Fri, 19 Sep 2014 13:18:56 -0400
Subject: 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.
---
doc/src/sgml/auto-explain.sgml | 77 ++++++++++++++++++++++++------------------
1 file changed, 44 insertions(+), 33 deletions(-)
(limited to 'doc/src')
diff --git a/doc/src/sgml/auto-explain.sgml b/doc/src/sgml/auto-explain.sgml
index 334996b0e66..d527208271f 100644
--- a/doc/src/sgml/auto-explain.sgml
+++ b/doc/src/sgml/auto-explain.sgml
@@ -81,6 +81,8 @@ 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 auto_explain.log_timing ameliorates the
+ performance cost, at the price of obtaining less information.
@@ -88,16 +90,19 @@ LOAD 'auto_explain';
- auto_explain.log_verbose (boolean)
+ auto_explain.log_buffers (boolean)
- auto_explain.log_verbose configuration parameter
+ auto_explain.log_buffers configuration parameter
- auto_explain.log_verbose causes EXPLAIN VERBOSE
- output, rather than just EXPLAIN output, to be printed
- when an execution plan is logged. This parameter is off by default.
+ auto_explain.log_buffers controls whether buffer
+ usage statistics are printed when an execution plan is logged; it's
+ equivalent to the BUFFERS option of EXPLAIN.
+ This parameter has no effect
+ unless auto_explain.log_analyze is enabled.
+ This parameter is off by default.
Only superusers can change this setting.
@@ -105,19 +110,24 @@ LOAD 'auto_explain';
- auto_explain.log_buffers (boolean)
+ auto_explain.log_timing (boolean)
- auto_explain.log_buffers configuration parameter
+ auto_explain.log_timing configuration parameter
- auto_explain.log_buffers causes EXPLAIN
- (ANALYZE, BUFFERS) output, rather than just 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 auto_explain.log_analyze
- parameter is set.
+ auto_explain.log_timing controls whether per-node
+ timing information is printed when an execution plan is logged; it's
+ equivalent to the TIMING option of 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 auto_explain.log_analyze is enabled.
+ This parameter is on by default.
+ Only superusers can change this setting.
@@ -133,26 +143,27 @@ LOAD 'auto_explain';
auto_explain.log_triggers causes trigger
execution statistics to be included when an execution plan is logged.
- This parameter is off by default. Only superusers can change this
- setting. This parameter has no effect unless
- auto_explain.log_analyze parameter is set.
+ This parameter has no effect
+ unless auto_explain.log_analyze is enabled.
+ This parameter is off by default.
+ Only superusers can change this setting.
- auto_explain.log_format (enum)
+ auto_explain.log_verbose (boolean)
- auto_explain.log_format configuration parameter
+ auto_explain.log_verbose configuration parameter
- auto_explain.log_format selects the
- EXPLAIN output format to be used.
- The allowed values are text, xml,
- json, and yaml. The default is text.
+ auto_explain.log_verbose controls whether verbose
+ details are printed when an execution plan is logged; it's
+ equivalent to the VERBOSE option of EXPLAIN.
+ This parameter is off by default.
Only superusers can change this setting.
@@ -160,25 +171,22 @@ LOAD 'auto_explain';
- auto_explain.log_timing (boolean)
+ auto_explain.log_format (enum)
- auto_explain.log_timing configuration parameter
+ auto_explain.log_format configuration parameter
- auto_explain.log_timing causes EXPLAIN
- (ANALYZE, TIMING off) output, rather than just 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 off when only actual row counts, and not exact times, are needed.
- This parameter is only effective when auto_explain.log_analyze
- is also enabled. This parameter is on by default.
+ auto_explain.log_format selects the
+ EXPLAIN output format to be used.
+ The allowed values are text, xml,
+ json, and yaml. The default is text.
Only superusers can change this setting.
-
+
auto_explain.log_nested_statements (boolean)
@@ -198,7 +206,9 @@ LOAD 'auto_explain';
- These parameters must be set in postgresql.conf.
+ In ordinary usage, these parameters are set
+ in postgresql.conf, although superusers can alter them
+ on-the-fly within their own sessions.
Typical usage might be:
@@ -216,6 +226,7 @@ auto_explain.log_min_duration = '3s'
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;
--
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