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| author | Alvaro Herrera <alvherre@alvh.no-ip.org> | 2018-11-29 18:42:53 -0300 |
|---|---|---|
| committer | Alvaro Herrera <alvherre@alvh.no-ip.org> | 2018-11-29 18:42:53 -0300 |
| commit | 88bdbd3f746049834ae3cc972e6e650586ec3c9d (patch) | |
| tree | 53a6007b47d766ac0e1309fa1fedc600411a51aa /src/backend/tcop/postgres.c | |
| parent | 826eff57c4c23f77314ba7151d3dc506ce0fa24c (diff) | |
| download | postgresql-88bdbd3f746049834ae3cc972e6e650586ec3c9d.tar.gz postgresql-88bdbd3f746049834ae3cc972e6e650586ec3c9d.zip | |
Add log_statement_sample_rate parameter
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
Diffstat (limited to 'src/backend/tcop/postgres.c')
| -rw-r--r-- | src/backend/tcop/postgres.c | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c index a3b9757565e..9a948f825df 100644 --- a/src/backend/tcop/postgres.c +++ b/src/backend/tcop/postgres.c @@ -2201,7 +2201,8 @@ check_log_statement(List *stmt_list) /* * check_log_duration - * Determine whether current command's duration should be logged + * Determine whether current command's duration should be logged. + * If log_statement_sample_rate < 1.0, log only a sample. * * Returns: * 0 if no logging is needed @@ -2223,6 +2224,7 @@ check_log_duration(char *msec_str, bool was_logged) int usecs; int msecs; bool exceeded; + bool in_sample; TimestampDifference(GetCurrentStatementStartTimestamp(), GetCurrentTimestamp(), @@ -2239,7 +2241,17 @@ check_log_duration(char *msec_str, bool was_logged) (secs > log_min_duration_statement / 1000 || secs * 1000 + msecs >= log_min_duration_statement))); - if (exceeded || log_duration) + /* + * 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) { snprintf(msec_str, 32, "%ld.%03d", secs * 1000 + msecs, usecs % 1000); |