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Add stats for min, max, mean, stddev times to pg_stat_statements. 

The new fields are min_time, max_time, mean_time and stddev_time.

Based on an original patch from Mitsumasa KONDO, modified by me. Reviewed by Petr Jelínek.
This commit is contained in:
Andrew Dunstan 2015-03-27 15:43:22 -04:00
parent 8816af65e4
commit 717f709532
6 changed files with 170 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
contrib/pg_stat_statements/Makefile
View File

@ -4,8 +4,9 @@ MODULE_big = pg_stat_statements
OBJS = pg_stat_statements.o $(WIN32RES)
EXTENSION = pg_stat_statements
DATA = pg_stat_statements--1.2.sql pg_stat_statements--1.1--1.2.sql \
pg_stat_statements--1.0--1.1.sql pg_stat_statements--unpackaged--1.0.sql
DATA = pg_stat_statements--1.3.sql pg_stat_statements--1.2--1.3.sql \
pg_stat_statements--1.1--1.2.sql pg_stat_statements--1.0--1.1.sql \
pg_stat_statements--unpackaged--1.0.sql
PGFILEDESC = "pg_stat_statements - execution statistics of SQL statements"
ifdef USE_PGXS

47
contrib/pg_stat_statements/pg_stat_statements--1.2--1.3.sql Normal file
View File

@ -0,0 +1,47 @@
/* contrib/pg_stat_statements/pg_stat_statements--1.2--1.3.sql */
-- complain if script is sourced in psql, rather than via ALTER EXTENSION
\echo Use "ALTER EXTENSION pg_stat_statements UPDATE TO '1.3'" to load this file. \quit
/* First we have to remove them from the extension */
ALTER EXTENSION pg_stat_statements DROP VIEW pg_stat_statements;
ALTER EXTENSION pg_stat_statements DROP FUNCTION pg_stat_statements(boolean);
/* Then we can drop them */
DROP VIEW pg_stat_statements;
DROP FUNCTION pg_stat_statements(boolean);
/* Now redefine */
CREATE FUNCTION pg_stat_statements(IN showtext boolean,
OUT userid oid,
OUT dbid oid,
OUT queryid bigint,
OUT query text,
OUT calls int8,
OUT total_time float8,
OUT min_time float8,
OUT max_time float8,
OUT mean_time float8,
OUT stddev_time float8,
OUT rows int8,
OUT shared_blks_hit int8,
OUT shared_blks_read int8,
OUT shared_blks_dirtied int8,
OUT shared_blks_written int8,
OUT local_blks_hit int8,
OUT local_blks_read int8,
OUT local_blks_dirtied int8,
OUT local_blks_written int8,
OUT temp_blks_read int8,
OUT temp_blks_written int8,
OUT blk_read_time float8,
OUT blk_write_time float8
)
RETURNS SETOF record
AS 'MODULE_PATHNAME', 'pg_stat_statements_1_3'
LANGUAGE C STRICT VOLATILE;
CREATE VIEW pg_stat_statements AS
SELECT * FROM pg_stat_statements(true);
GRANT SELECT ON pg_stat_statements TO PUBLIC;

8
contrib/pg_stat_statements/pg_stat_statements--1.2.sql → contrib/pg_stat_statements/pg_stat_statements--1.3.sql
View File

@ -1,4 +1,4 @@
/* contrib/pg_stat_statements/pg_stat_statements--1.2.sql */
/* contrib/pg_stat_statements/pg_stat_statements--1.3.sql */
-- complain if script is sourced in psql, rather than via CREATE EXTENSION
\echo Use "CREATE EXTENSION pg_stat_statements" to load this file. \quit
@ -16,6 +16,10 @@ CREATE FUNCTION pg_stat_statements(IN showtext boolean,
OUT query text,
OUT calls int8,
OUT total_time float8,
OUT min_time float8,
OUT max_time float8,
OUT mean_time float8,
OUT stddev_time float8,
OUT rows int8,
OUT shared_blks_hit int8,
OUT shared_blks_read int8,
@ -31,7 +35,7 @@ CREATE FUNCTION pg_stat_statements(IN showtext boolean,
OUT blk_write_time float8
)
RETURNS SETOF record
AS 'MODULE_PATHNAME', 'pg_stat_statements_1_2'
AS 'MODULE_PATHNAME', 'pg_stat_statements_1_3'
LANGUAGE C STRICT VOLATILE;
-- Register a view on the function for ease of use.

87
contrib/pg_stat_statements/pg_stat_statements.c
View File

@ -115,7 +115,8 @@ typedef enum pgssVersion
{
PGSS_V1_0 = 0,
PGSS_V1_1,
PGSS_V1_2
PGSS_V1_2,
PGSS_V1_3
} pgssVersion;
/*
@ -136,6 +137,10 @@ typedef struct Counters
{
int64 calls; /* # of times executed */
double total_time; /* total execution time, in msec */
double min_time; /* minimim execution time in msec */
double max_time; /* maximum execution time in msec */
double mean_time; /* mean execution time in msec */
double sum_var_time; /* sum of variances in execution time in msec */
int64 rows; /* total # of retrieved or affected rows */
int64 shared_blks_hit; /* # of shared buffer hits */
int64 shared_blks_read; /* # of shared disk blocks read */
@ -274,6 +279,7 @@ void _PG_fini(void);
PG_FUNCTION_INFO_V1(pg_stat_statements_reset);
PG_FUNCTION_INFO_V1(pg_stat_statements_1_2);
PG_FUNCTION_INFO_V1(pg_stat_statements_1_3);
PG_FUNCTION_INFO_V1(pg_stat_statements);
static void pgss_shmem_startup(void);
@ -320,6 +326,7 @@ static char *generate_normalized_query(pgssJumbleState *jstate, const char *quer
int *query_len_p, int encoding);
static void fill_in_constant_lengths(pgssJumbleState *jstate, const char *query);
static int comp_location(const void *a, const void *b);
static inline double sqrtd(const double x);
/*
@ -1215,6 +1222,32 @@ pgss_store(const char *query, uint32 queryId,
e->counters.calls += 1;
e->counters.total_time += total_time;
if (e->counters.calls == 1)
{
e->counters.min_time = total_time;
e->counters.max_time = total_time;
e->counters.mean_time = total_time;
}
else
{
/*
* Welford's method for accurately computing variance.
* See <http://www.johndcook.com/blog/standard_deviation/>
*/
double old_mean = e->counters.mean_time;
e->counters.mean_time +=
(total_time - old_mean) / e->counters.calls;
e->counters.sum_var_time +=
(total_time - old_mean) * (total_time - e->counters.mean_time);
/* calculate min and max time */
if (e->counters.min_time > total_time)
e->counters.min_time = total_time;
if (e->counters.max_time < total_time)
e->counters.max_time = total_time;
}
e->counters.rows += rows;
e->counters.shared_blks_hit += bufusage->shared_blks_hit;
e->counters.shared_blks_read += bufusage->shared_blks_read;
@ -1259,7 +1292,8 @@ pg_stat_statements_reset(PG_FUNCTION_ARGS)
#define PG_STAT_STATEMENTS_COLS_V1_0 14
#define PG_STAT_STATEMENTS_COLS_V1_1 18
#define PG_STAT_STATEMENTS_COLS_V1_2 19
#define PG_STAT_STATEMENTS_COLS 19 /* maximum of above */
#define PG_STAT_STATEMENTS_COLS_V1_3 23
#define PG_STAT_STATEMENTS_COLS 23 /* maximum of above */
/*
* Retrieve statement statistics.
@ -1271,6 +1305,16 @@ pg_stat_statements_reset(PG_FUNCTION_ARGS)
* expected API version is identified by embedding it in the C name of the
* function. Unfortunately we weren't bright enough to do that for 1.1.
*/
Datum
pg_stat_statements_1_3(PG_FUNCTION_ARGS)
{
bool showtext = PG_GETARG_BOOL(0);
pg_stat_statements_internal(fcinfo, PGSS_V1_3, showtext);
return (Datum) 0;
}
Datum
pg_stat_statements_1_2(PG_FUNCTION_ARGS)
{
@ -1360,6 +1404,10 @@ pg_stat_statements_internal(FunctionCallInfo fcinfo,
if (api_version != PGSS_V1_2)
elog(ERROR, "incorrect number of output arguments");
break;
case PG_STAT_STATEMENTS_COLS_V1_3:
if (api_version != PGSS_V1_3)
elog(ERROR, "incorrect number of output arguments");
break;
default:
elog(ERROR, "incorrect number of output arguments");
}
@ -1519,6 +1567,23 @@ pg_stat_statements_internal(FunctionCallInfo fcinfo,
values[i++] = Int64GetDatumFast(tmp.calls);
values[i++] = Float8GetDatumFast(tmp.total_time);
if (api_version >= PGSS_V1_3)
{
values[i++] = Float8GetDatumFast(tmp.min_time);
values[i++] = Float8GetDatumFast(tmp.max_time);
values[i++] = Float8GetDatumFast(tmp.mean_time);
/*
* Note we are calculating the population variance here, not the
* sample variance, as we have data for the whole population,
* so Bessel's correction is not used, and we don't divide by
* tmp.calls - 1.
*/
if (tmp.calls > 1)
values[i++] =
Float8GetDatumFast(sqrtd(tmp.sum_var_time / tmp.calls));
else
values[i++] = Float8GetDatumFast(0.0);
}
values[i++] = Int64GetDatumFast(tmp.rows);
values[i++] = Int64GetDatumFast(tmp.shared_blks_hit);
values[i++] = Int64GetDatumFast(tmp.shared_blks_read);
@ -1541,6 +1606,7 @@ pg_stat_statements_internal(FunctionCallInfo fcinfo,
Assert(i == (api_version == PGSS_V1_0 ? PG_STAT_STATEMENTS_COLS_V1_0 :
api_version == PGSS_V1_1 ? PG_STAT_STATEMENTS_COLS_V1_1 :
api_version == PGSS_V1_2 ? PG_STAT_STATEMENTS_COLS_V1_2 :
api_version == PGSS_V1_3 ? PG_STAT_STATEMENTS_COLS_V1_3 :
-1 /* fail if you forget to update this assert */ ));
tuplestore_putvalues(tupstore, tupdesc, values, nulls);
@ -2899,3 +2965,20 @@ comp_location(const void *a, const void *b)
else
return 0;
}
/*
* fast sqrt algorithm: reference from Fast inverse square root algorithms.
*/
static inline double
sqrtd(const double x)
{
double x_half = 0.5 * x;
long long int tmp = 0x5FE6EB50C7B537AAl - ( *(long long int*)&x >> 1);
double x_result = * (double*)&tmp;
x_result *= (1.5 - (x_half * x_result * x_result));
/* If retry this calculation, it becomes higher precision at sqrt */
x_result *= (1.5 - (x_half * x_result * x_result));
return x_result * x;
}

2
contrib/pg_stat_statements/pg_stat_statements.control
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@ -1,5 +1,5 @@
# pg_stat_statements extension
comment = 'track execution statistics of all SQL statements executed'
default_version = '1.2'
default_version = '1.3'
module_pathname = '$libdir/pg_stat_statements'
relocatable = true

28
doc/src/sgml/pgstatstatements.sgml
View File

@ -86,6 +86,34 @@
<entry>Total time spent in the statement, in milliseconds</entry>
</row>
<row>
<entry><structfield>min_time</structfield></entry>
<entry><type>double precision</type></entry>
<entry></entry>
<entry>Minimum time spent in the statement, in milliseconds</entry>
</row>
<row>
<entry><structfield>max_time</structfield></entry>
<entry><type>double precision</type></entry>
<entry></entry>
<entry>Maximum time spent in the statement, in milliseconds</entry>
</row>
<row>
<entry><structfield>mean_time</structfield></entry>
<entry><type>double precision</type></entry>
<entry></entry>
<entry>Mean time spent in the statement, in milliseconds</entry>
</row>
<row>
<entry><structfield>stddev_time</structfield></entry>
<entry><type>double precision</type></entry>
<entry></entry>
<entry>Population standard deviation of time spent in the statement, in milliseconds</entry>
</row>
<row>
<entry><structfield>rows</structfield></entry>
<entry><type>bigint</type></entry>