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Revert "Add log_statement_sample_rate parameter"

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This reverts commit 88bdbd3f74.

As committed, statement sampling used the existing duration threshold
(log_min_duration_statement) when decide which statements to sample.
The issue is that even the longest statements are subject to sampling,
and so may not end up logged. An improvement was proposed, introducing
a second duration threshold, but it would not be backwards compatible.
So we've decided to revert this feature - the separate threshold should
be part of the feature itself.

Discussion: https://postgr.es/m/CAFj8pRDS8tQ3Wviw9%3DAvODyUciPSrGeMhJi_WPE%2BEB8%2B4gLL-Q%40mail.gmail.com
This commit is contained in:
Tomas Vondra
2019-08-04 20:29:00 +02:00
parent 4f9ed8f3c5
commit 75506195da
5 changed files with 13 additions and 65 deletions
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16
src/backend/tcop/postgres.c
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@ -2212,8 +2212,7 @@ check_log_statement(List *stmt_list)
/*
* check_log_duration
* Determine whether current command's duration should be logged.
* If log_statement_sample_rate < 1.0, log only a sample.
* Determine whether current command's duration should be logged
* We also check if this statement in this transaction must be logged
* (regardless of its duration).
*
@ -2237,7 +2236,6 @@ check_log_duration(char *msec_str, bool was_logged)
int usecs;
int msecs;
bool exceeded;
bool in_sample;
TimestampDifference(GetCurrentStatementStartTimestamp(),
GetCurrentTimestamp(),
@ -2254,17 +2252,7 @@ check_log_duration(char *msec_str, bool was_logged)
(secs > log_min_duration_statement / 1000 ||
secs * 1000 + msecs >= log_min_duration_statement)));
/*
* Do not log if log_statement_sample_rate = 0. Log a sample if
* log_statement_sample_rate <= 1 and avoid unecessary random() call
* if log_statement_sample_rate = 1.
*/
if (exceeded)
in_sample = log_statement_sample_rate != 0 &&
(log_statement_sample_rate == 1 ||
random() <= log_statement_sample_rate * MAX_RANDOM_VALUE);
if ((exceeded && in_sample) || log_duration || xact_is_sampled)
if (exceeded || log_duration || xact_is_sampled)
{
snprintf(msec_str, 32, "%ld.%03d",
secs * 1000 + msecs, usecs % 1000);