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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.
1 parent 8816af6 commit 717f709

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6 files changed

+170
-7
lines changed

6 files changed

+170
-7
lines changed

‎contrib/pg_stat_statements/Makefile

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -4,8 +4,9 @@ MODULE_big = pg_stat_statements
44
OBJS = pg_stat_statements.o $(WIN32RES)
55

66
EXTENSION = pg_stat_statements
7-
DATA = pg_stat_statements--1.2.sql pg_stat_statements--1.1--1.2.sql \
8-
pg_stat_statements--1.0--1.1.sql pg_stat_statements--unpackaged--1.0.sql
7+
DATA = pg_stat_statements--1.3.sql pg_stat_statements--1.2--1.3.sql \
8+
pg_stat_statements--1.1--1.2.sql pg_stat_statements--1.0--1.1.sql \
9+
pg_stat_statements--unpackaged--1.0.sql
910
PGFILEDESC = "pg_stat_statements - execution statistics of SQL statements"
1011

1112
ifdef USE_PGXS

‎contrib/pg_stat_statements/pg_stat_statements--1.2--1.3.sql

Lines changed: 47 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,47 @@
1+
/* contrib/pg_stat_statements/pg_stat_statements--1.2--1.3.sql */
2+
3+
-- complain if script is sourced in psql, rather than via ALTER EXTENSION
4+
\echo Use "ALTER EXTENSION pg_stat_statements UPDATE TO '1.3'" to load this file. \quit
5+
6+
/* First we have to remove them from the extension */
7+
ALTER EXTENSION pg_stat_statements DROP VIEW pg_stat_statements;
8+
ALTER EXTENSION pg_stat_statements DROP FUNCTION pg_stat_statements(boolean);
9+
10+
/* Then we can drop them */
11+
DROP VIEW pg_stat_statements;
12+
DROP FUNCTION pg_stat_statements(boolean);
13+
14+
/* Now redefine */
15+
CREATE FUNCTION pg_stat_statements(IN showtext boolean,
16+
OUT userid oid,
17+
OUT dbid oid,
18+
OUT queryid bigint,
19+
OUT query text,
20+
OUT calls int8,
21+
OUT total_time float8,
22+
OUT min_time float8,
23+
OUT max_time float8,
24+
OUT mean_time float8,
25+
OUT stddev_time float8,
26+
OUT rows int8,
27+
OUT shared_blks_hit int8,
28+
OUT shared_blks_read int8,
29+
OUT shared_blks_dirtied int8,
30+
OUT shared_blks_written int8,
31+
OUT local_blks_hit int8,
32+
OUT local_blks_read int8,
33+
OUT local_blks_dirtied int8,
34+
OUT local_blks_written int8,
35+
OUT temp_blks_read int8,
36+
OUT temp_blks_written int8,
37+
OUT blk_read_time float8,
38+
OUT blk_write_time float8
39+
)
40+
RETURNS SETOF record
41+
AS 'MODULE_PATHNAME', 'pg_stat_statements_1_3'
42+
LANGUAGE C STRICT VOLATILE;
43+
44+
CREATE VIEW pg_stat_statements AS
45+
SELECT * FROM pg_stat_statements(true);
46+
47+
GRANT SELECT ON pg_stat_statements TO PUBLIC;

‎contrib/pg_stat_statements/pg_stat_statements--1.2.sql renamed to ‎contrib/pg_stat_statements/pg_stat_statements--1.3.sql

Lines changed: 6 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
/* contrib/pg_stat_statements/pg_stat_statements--1.2.sql */
1+
/* contrib/pg_stat_statements/pg_stat_statements--1.3.sql */
22

33
-- complain if script is sourced in psql, rather than via CREATE EXTENSION
44
\echo Use "CREATE EXTENSION pg_stat_statements" to load this file. \quit
@@ -16,6 +16,10 @@ CREATE FUNCTION pg_stat_statements(IN showtext boolean,
1616
OUT query text,
1717
OUT calls int8,
1818
OUT total_time float8,
19+
OUT min_time float8,
20+
OUT max_time float8,
21+
OUT mean_time float8,
22+
OUT stddev_time float8,
1923
OUT rows int8,
2024
OUT shared_blks_hit int8,
2125
OUT shared_blks_read int8,
@@ -31,7 +35,7 @@ CREATE FUNCTION pg_stat_statements(IN showtext boolean,
3135
OUT blk_write_time float8
3236
)
3337
RETURNS SETOF record
34-
AS 'MODULE_PATHNAME', 'pg_stat_statements_1_2'
38+
AS 'MODULE_PATHNAME', 'pg_stat_statements_1_3'
3539
LANGUAGE C STRICT VOLATILE;
3640

3741
-- Register a view on the function for ease of use.

‎contrib/pg_stat_statements/pg_stat_statements.c

Lines changed: 85 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -115,7 +115,8 @@ typedef enum pgssVersion
115115
{
116116
PGSS_V1_0 = 0,
117117
PGSS_V1_1,
118-
PGSS_V1_2
118+
PGSS_V1_2,
119+
PGSS_V1_3
119120
} pgssVersion;
120121

121122
/*
@@ -136,6 +137,10 @@ typedef struct Counters
136137
{
137138
int64 calls; /* # of times executed */
138139
double total_time; /* total execution time, in msec */
140+
double min_time; /* minimim execution time in msec */
141+
double max_time; /* maximum execution time in msec */
142+
double mean_time; /* mean execution time in msec */
143+
double sum_var_time; /* sum of variances in execution time in msec */
139144
int64 rows; /* total # of retrieved or affected rows */
140145
int64 shared_blks_hit; /* # of shared buffer hits */
141146
int64 shared_blks_read; /* # of shared disk blocks read */
@@ -274,6 +279,7 @@ void _PG_fini(void);
274279

275280
PG_FUNCTION_INFO_V1(pg_stat_statements_reset);
276281
PG_FUNCTION_INFO_V1(pg_stat_statements_1_2);
282+
PG_FUNCTION_INFO_V1(pg_stat_statements_1_3);
277283
PG_FUNCTION_INFO_V1(pg_stat_statements);
278284

279285
static void pgss_shmem_startup(void);
@@ -320,6 +326,7 @@ static char *generate_normalized_query(pgssJumbleState *jstate, const char *quer
320326
int *query_len_p, int encoding);
321327
static void fill_in_constant_lengths(pgssJumbleState *jstate, const char *query);
322328
static int comp_location(const void *a, const void *b);
329+
static inline double sqrtd(const double x);
323330

324331

325332
/*
@@ -1215,6 +1222,32 @@ pgss_store(const char *query, uint32 queryId,
12151222

12161223
e->counters.calls += 1;
12171224
e->counters.total_time += total_time;
1225+
if (e->counters.calls == 1)
1226+
{
1227+
e->counters.min_time = total_time;
1228+
e->counters.max_time = total_time;
1229+
e->counters.mean_time = total_time;
1230+
}
1231+
else
1232+
{
1233+
/*
1234+
* Welford's method for accurately computing variance.
1235+
* See <http://www.johndcook.com/blog/standard_deviation/>
1236+
*/
1237+
double old_mean = e->counters.mean_time;
1238+
1239+
e->counters.mean_time +=
1240+
(total_time - old_mean) / e->counters.calls;
1241+
e->counters.sum_var_time +=
1242+
(total_time - old_mean) * (total_time - e->counters.mean_time);
1243+
1244+
/* calculate min and max time */
1245+
if (e->counters.min_time > total_time)
1246+
e->counters.min_time = total_time;
1247+
if (e->counters.max_time < total_time)
1248+
e->counters.max_time = total_time;
1249+
1250+
}
12181251
e->counters.rows += rows;
12191252
e->counters.shared_blks_hit += bufusage->shared_blks_hit;
12201253
e->counters.shared_blks_read += bufusage->shared_blks_read;
@@ -1259,7 +1292,8 @@ pg_stat_statements_reset(PG_FUNCTION_ARGS)
12591292
#define PG_STAT_STATEMENTS_COLS_V1_0 14
12601293
#define PG_STAT_STATEMENTS_COLS_V1_1 18
12611294
#define PG_STAT_STATEMENTS_COLS_V1_2 19
1262-
#define PG_STAT_STATEMENTS_COLS 19 /* maximum of above */
1295+
#define PG_STAT_STATEMENTS_COLS_V1_3 23
1296+
#define PG_STAT_STATEMENTS_COLS 23 /* maximum of above */
12631297

12641298
/*
12651299
* Retrieve statement statistics.
@@ -1271,6 +1305,16 @@ pg_stat_statements_reset(PG_FUNCTION_ARGS)
12711305
* expected API version is identified by embedding it in the C name of the
12721306
* function. Unfortunately we weren't bright enough to do that for 1.1.
12731307
*/
1308+
Datum
1309+
pg_stat_statements_1_3(PG_FUNCTION_ARGS)
1310+
{
1311+
bool showtext = PG_GETARG_BOOL(0);
1312+
1313+
pg_stat_statements_internal(fcinfo, PGSS_V1_3, showtext);
1314+
1315+
return (Datum) 0;
1316+
}
1317+
12741318
Datum
12751319
pg_stat_statements_1_2(PG_FUNCTION_ARGS)
12761320
{
@@ -1360,6 +1404,10 @@ pg_stat_statements_internal(FunctionCallInfo fcinfo,
13601404
if (api_version != PGSS_V1_2)
13611405
elog(ERROR, "incorrect number of output arguments");
13621406
break;
1407+
case PG_STAT_STATEMENTS_COLS_V1_3:
1408+
if (api_version != PGSS_V1_3)
1409+
elog(ERROR, "incorrect number of output arguments");
1410+
break;
13631411
default:
13641412
elog(ERROR, "incorrect number of output arguments");
13651413
}
@@ -1519,6 +1567,23 @@ pg_stat_statements_internal(FunctionCallInfo fcinfo,
15191567

15201568
values[i++] = Int64GetDatumFast(tmp.calls);
15211569
values[i++] = Float8GetDatumFast(tmp.total_time);
1570+
if (api_version >= PGSS_V1_3)
1571+
{
1572+
values[i++] = Float8GetDatumFast(tmp.min_time);
1573+
values[i++] = Float8GetDatumFast(tmp.max_time);
1574+
values[i++] = Float8GetDatumFast(tmp.mean_time);
1575+
/*
1576+
* Note we are calculating the population variance here, not the
1577+
* sample variance, as we have data for the whole population,
1578+
* so Bessel's correction is not used, and we don't divide by
1579+
* tmp.calls - 1.
1580+
*/
1581+
if (tmp.calls > 1)
1582+
values[i++] =
1583+
Float8GetDatumFast(sqrtd(tmp.sum_var_time / tmp.calls));
1584+
else
1585+
values[i++] = Float8GetDatumFast(0.0);
1586+
}
15221587
values[i++] = Int64GetDatumFast(tmp.rows);
15231588
values[i++] = Int64GetDatumFast(tmp.shared_blks_hit);
15241589
values[i++] = Int64GetDatumFast(tmp.shared_blks_read);
@@ -1541,6 +1606,7 @@ pg_stat_statements_internal(FunctionCallInfo fcinfo,
15411606
Assert(i == (api_version == PGSS_V1_0 ? PG_STAT_STATEMENTS_COLS_V1_0 :
15421607
api_version == PGSS_V1_1 ? PG_STAT_STATEMENTS_COLS_V1_1 :
15431608
api_version == PGSS_V1_2 ? PG_STAT_STATEMENTS_COLS_V1_2 :
1609+
api_version == PGSS_V1_3 ? PG_STAT_STATEMENTS_COLS_V1_3 :
15441610
-1 /* fail if you forget to update this assert */ ));
15451611

15461612
tuplestore_putvalues(tupstore, tupdesc, values, nulls);
@@ -2899,3 +2965,20 @@ comp_location(const void *a, const void *b)
28992965
else
29002966
return 0;
29012967
}
2968+
2969+
/*
2970+
* fast sqrt algorithm: reference from Fast inverse square root algorithms.
2971+
*/
2972+
static inline double
2973+
sqrtd(const double x)
2974+
{
2975+
double x_half = 0.5 * x;
2976+
long long int tmp = 0x5FE6EB50C7B537AAl - ( *(long long int*)&x >> 1);
2977+
double x_result = * (double*)&tmp;
2978+
2979+
x_result *= (1.5 - (x_half * x_result * x_result));
2980+
/* If retry this calculation, it becomes higher precision at sqrt */
2981+
x_result *= (1.5 - (x_half * x_result * x_result));
2982+
2983+
return x_result * x;
2984+
}

‎contrib/pg_stat_statements/pg_stat_statements.control

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
# pg_stat_statements extension
22
comment = 'track execution statistics of all SQL statements executed'
3-
default_version = '1.2'
3+
default_version = '1.3'
44
module_pathname = '$libdir/pg_stat_statements'
55
relocatable = true

‎doc/src/sgml/pgstatstatements.sgml

Lines changed: 28 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -86,6 +86,34 @@
8686
<entry>Total time spent in the statement, in milliseconds</entry>
8787
</row>
8888

89+
<row>
90+
<entry><structfield>min_time</structfield></entry>
91+
<entry><type>double precision</type></entry>
92+
<entry></entry>
93+
<entry>Minimum time spent in the statement, in milliseconds</entry>
94+
</row>
95+
96+
<row>
97+
<entry><structfield>max_time</structfield></entry>
98+
<entry><type>double precision</type></entry>
99+
<entry></entry>
100+
<entry>Maximum time spent in the statement, in milliseconds</entry>
101+
</row>
102+
103+
<row>
104+
<entry><structfield>mean_time</structfield></entry>
105+
<entry><type>double precision</type></entry>
106+
<entry></entry>
107+
<entry>Mean time spent in the statement, in milliseconds</entry>
108+
</row>
109+
110+
<row>
111+
<entry><structfield>stddev_time</structfield></entry>
112+
<entry><type>double precision</type></entry>
113+
<entry></entry>
114+
<entry>Population standard deviation of time spent in the statement, in milliseconds</entry>
115+
</row>
116+
89117
<row>
90118
<entry><structfield>rows</structfield></entry>
91119
<entry><type>bigint</type></entry>

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