1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
|
--
-- Test Statistics Collector
--
-- Must be run after tenk2 has been created (by create_table),
-- populated (by create_misc) and indexed (by create_index).
--
-- conditio sine qua non
SHOW track_counts; -- must be on
track_counts
--------------
on
(1 row)
-- ensure that both seqscan and indexscan plans are allowed
SET enable_seqscan TO on;
SET enable_indexscan TO on;
-- for the moment, we don't want index-only scans here
SET enable_indexonlyscan TO off;
-- save counters
CREATE TABLE prevstats AS
SELECT t.seq_scan, t.seq_tup_read, t.idx_scan, t.idx_tup_fetch,
(b.heap_blks_read + b.heap_blks_hit) AS heap_blks,
(b.idx_blks_read + b.idx_blks_hit) AS idx_blks,
pg_stat_get_snapshot_timestamp() as snap_ts
FROM pg_catalog.pg_stat_user_tables AS t,
pg_catalog.pg_statio_user_tables AS b
WHERE t.relname='tenk2' AND b.relname='tenk2';
-- function to wait for counters to advance
create function wait_for_stats() returns void as $$
declare
start_time timestamptz := clock_timestamp();
updated1 bool;
updated2 bool;
updated3 bool;
updated4 bool;
begin
-- we don't want to wait forever; loop will exit after 30 seconds
for i in 1 .. 300 loop
-- With parallel query, the seqscan and indexscan on tenk2 might be done
-- in parallel worker processes, which will send their stats counters
-- asynchronously to what our own session does. So we must check for
-- those counts to be registered separately from the update counts.
-- check to see if seqscan has been sensed
SELECT (st.seq_scan >= pr.seq_scan + 1) INTO updated1
FROM pg_stat_user_tables AS st, pg_class AS cl, prevstats AS pr
WHERE st.relname='tenk2' AND cl.relname='tenk2';
-- check to see if indexscan has been sensed
SELECT (st.idx_scan >= pr.idx_scan + 1) INTO updated2
FROM pg_stat_user_tables AS st, pg_class AS cl, prevstats AS pr
WHERE st.relname='tenk2' AND cl.relname='tenk2';
-- check to see if all updates have been sensed
SELECT (n_tup_ins > 0) INTO updated3
FROM pg_stat_user_tables WHERE relname='trunc_stats_test4';
-- We must also check explicitly that pg_stat_get_snapshot_timestamp has
-- advanced, because that comes from the global stats file which might
-- be older than the per-DB stats file we got the other values from.
SELECT (pr.snap_ts < pg_stat_get_snapshot_timestamp()) INTO updated4
FROM prevstats AS pr;
exit when updated1 and updated2 and updated3 and updated4;
-- wait a little
perform pg_sleep_for('100 milliseconds');
-- reset stats snapshot so we can test again
perform pg_stat_clear_snapshot();
end loop;
-- report time waited in postmaster log (where it won't change test output)
raise log 'wait_for_stats delayed % seconds',
extract(epoch from clock_timestamp() - start_time);
end
$$ language plpgsql;
-- test effects of TRUNCATE on n_live_tup/n_dead_tup counters
CREATE TABLE trunc_stats_test(id serial);
CREATE TABLE trunc_stats_test1(id serial, stuff text);
CREATE TABLE trunc_stats_test2(id serial);
CREATE TABLE trunc_stats_test3(id serial, stuff text);
CREATE TABLE trunc_stats_test4(id serial);
-- check that n_live_tup is reset to 0 after truncate
INSERT INTO trunc_stats_test DEFAULT VALUES;
INSERT INTO trunc_stats_test DEFAULT VALUES;
INSERT INTO trunc_stats_test DEFAULT VALUES;
TRUNCATE trunc_stats_test;
-- test involving a truncate in a transaction; 4 ins but only 1 live
INSERT INTO trunc_stats_test1 DEFAULT VALUES;
INSERT INTO trunc_stats_test1 DEFAULT VALUES;
INSERT INTO trunc_stats_test1 DEFAULT VALUES;
UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
DELETE FROM trunc_stats_test1 WHERE id = 3;
BEGIN;
UPDATE trunc_stats_test1 SET id = id + 100;
TRUNCATE trunc_stats_test1;
INSERT INTO trunc_stats_test1 DEFAULT VALUES;
COMMIT;
-- use a savepoint: 1 insert, 1 live
BEGIN;
INSERT INTO trunc_stats_test2 DEFAULT VALUES;
INSERT INTO trunc_stats_test2 DEFAULT VALUES;
SAVEPOINT p1;
INSERT INTO trunc_stats_test2 DEFAULT VALUES;
TRUNCATE trunc_stats_test2;
INSERT INTO trunc_stats_test2 DEFAULT VALUES;
RELEASE SAVEPOINT p1;
COMMIT;
-- rollback a savepoint: this should count 4 inserts and have 2
-- live tuples after commit (and 2 dead ones due to aborted subxact)
BEGIN;
INSERT INTO trunc_stats_test3 DEFAULT VALUES;
INSERT INTO trunc_stats_test3 DEFAULT VALUES;
SAVEPOINT p1;
INSERT INTO trunc_stats_test3 DEFAULT VALUES;
INSERT INTO trunc_stats_test3 DEFAULT VALUES;
TRUNCATE trunc_stats_test3;
INSERT INTO trunc_stats_test3 DEFAULT VALUES;
ROLLBACK TO SAVEPOINT p1;
COMMIT;
-- rollback a truncate: this should count 2 inserts and produce 2 dead tuples
BEGIN;
INSERT INTO trunc_stats_test4 DEFAULT VALUES;
INSERT INTO trunc_stats_test4 DEFAULT VALUES;
TRUNCATE trunc_stats_test4;
INSERT INTO trunc_stats_test4 DEFAULT VALUES;
ROLLBACK;
-- do a seqscan
SELECT count(*) FROM tenk2;
count
-------
10000
(1 row)
-- do an indexscan
-- make sure it is not a bitmap scan, which might skip fetching heap tuples
SET enable_bitmapscan TO off;
SELECT count(*) FROM tenk2 WHERE unique1 = 1;
count
-------
1
(1 row)
RESET enable_bitmapscan;
-- We can't just call wait_for_stats() at this point, because we only
-- transmit stats when the session goes idle, and we probably didn't
-- transmit the last couple of counts yet thanks to the rate-limiting logic
-- in pgstat_report_stat(). But instead of waiting for the rate limiter's
-- timeout to elapse, let's just start a new session. The old one will
-- then send its stats before dying.
\c -
-- wait for stats collector to update
SELECT wait_for_stats();
wait_for_stats
----------------
(1 row)
-- check effects
SELECT relname, n_tup_ins, n_tup_upd, n_tup_del, n_live_tup, n_dead_tup
FROM pg_stat_user_tables
WHERE relname like 'trunc_stats_test%' order by relname;
relname | n_tup_ins | n_tup_upd | n_tup_del | n_live_tup | n_dead_tup
-------------------+-----------+-----------+-----------+------------+------------
trunc_stats_test | 3 | 0 | 0 | 0 | 0
trunc_stats_test1 | 4 | 2 | 1 | 1 | 0
trunc_stats_test2 | 1 | 0 | 0 | 1 | 0
trunc_stats_test3 | 4 | 0 | 0 | 2 | 2
trunc_stats_test4 | 2 | 0 | 0 | 0 | 2
(5 rows)
SELECT st.seq_scan >= pr.seq_scan + 1,
st.seq_tup_read >= pr.seq_tup_read + cl.reltuples,
st.idx_scan >= pr.idx_scan + 1,
st.idx_tup_fetch >= pr.idx_tup_fetch + 1
FROM pg_stat_user_tables AS st, pg_class AS cl, prevstats AS pr
WHERE st.relname='tenk2' AND cl.relname='tenk2';
?column? | ?column? | ?column? | ?column?
----------+----------+----------+----------
t | t | t | t
(1 row)
SELECT st.heap_blks_read + st.heap_blks_hit >= pr.heap_blks + cl.relpages,
st.idx_blks_read + st.idx_blks_hit >= pr.idx_blks + 1
FROM pg_statio_user_tables AS st, pg_class AS cl, prevstats AS pr
WHERE st.relname='tenk2' AND cl.relname='tenk2';
?column? | ?column?
----------+----------
t | t
(1 row)
SELECT pr.snap_ts < pg_stat_get_snapshot_timestamp() as snapshot_newer
FROM prevstats AS pr;
snapshot_newer
----------------
t
(1 row)
DROP TABLE trunc_stats_test, trunc_stats_test1, trunc_stats_test2, trunc_stats_test3, trunc_stats_test4;
DROP TABLE prevstats;
-- End of Stats Test
|
