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Add log_statement_sample_rate parameter

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This allows to set a lower log_min_duration_statement value without
incurring excessive log traffic (which reduces performance).  This can
be useful to analyze workloads with lots of short queries.

Author: Adrien Nayrat
Reviewed-by: David Rowley, Vik Fearing
Discussion: https://postgr.es/m/c30ee535-ee1e-db9f-fa97-146b9f62caed@anayrat.info
This commit is contained in:
Alvaro Herrera
2018-11-29 18:42:53 -03:00
parent 826eff57c4
commit 88bdbd3f74
5 changed files with 61 additions and 12 deletions
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15
src/backend/utils/misc/guc.c
View File

@@ -486,6 +486,7 @@ int log_min_messages = WARNING;
int client_min_messages = NOTICE;
int log_min_duration_statement = -1;
int log_temp_files = -1;
double log_statement_sample_rate = 1.0;
int trace_recovery_messages = LOG;
int temp_file_limit = -1;
@@ -2642,7 +2643,8 @@ static struct config_int ConfigureNamesInt[] =
{"log_min_duration_statement", PGC_SUSET, LOGGING_WHEN,
gettext_noop("Sets the minimum execution time above which "
"statements will be logged."),
gettext_noop("Zero prints all queries. -1 turns this feature off."),
gettext_noop("Zero prints all queries, subject to log_statement_sample_rate. "
"-1 turns this feature off."),
GUC_UNIT_MS
},
&log_min_duration_statement,
@@ -3319,6 +3321,17 @@ static struct config_real ConfigureNamesReal[] =
NULL, NULL, NULL
},
{
{"log_statement_sample_rate", PGC_SUSET, LOGGING_WHEN,
gettext_noop("Fraction of statements over log_min_duration_statement to log."),
gettext_noop("If you only want a sample, use a value between 0 (never "
"log) and 1.0 (always log).")
},
&log_statement_sample_rate,
1.0, 0.0, 1.0,
NULL, NULL, NULL
},
/* End-of-list marker */
{
{NULL, 0, 0, NULL, NULL}, NULL, 0.0, 0.0, 0.0, NULL, NULL, NULL

11
src/backend/utils/misc/postgresql.conf.sample
View File

@@ -483,11 +483,14 @@
# fatal
# panic (effectively off)
#log_min_duration_statement = -1 # -1 is disabled, 0 logs all statements
# and their durations, > 0 logs only
# statements running at least this number
# of milliseconds
#log_min_duration_statement = -1 # logs statements and their durations
# according to log_statement_sample_rate. -1 is disabled,
# 0 logs all statement, > 0 logs only statements running at
# least this number of milliseconds.
#log_statement_sample_rate = 1 # Fraction of logged statements over
# log_min_duration_statement. 1.0 logs all statements,
# 0 never logs.
# - What to Log -