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9.5: pg_stat_statement and pgbench execution time discrepancies

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Hi,

During performance tests it was mentioned that pgbench common results are being different from what pg_stat_statements provides.

PostgreSQL version 9.5.3, centos 7.2. First run after pg_stat_extension created and first pgbench run.

pgbench -c 30 -T 300 -U postgres -P 10 -r -v
statement latencies in milliseconds:
        0.003431        \set nbranches 1 * :scale
        0.001046        \set ntellers 10 * :scale
        0.000891        \set naccounts 100000 * :scale
        0.001356        \setrandom aid 1 :naccounts
        0.000938        \setrandom bid 1 :nbranches
        0.000879        \setrandom tid 1 :ntellers
        0.000974        \setrandom delta -5000 5000
        0.102258        BEGIN;
        0.228744        UPDATE pgbench_accounts SET abalance = abalance + :delta WHERE aid = :aid;
        0.156087        SELECT abalance FROM pgbench_accounts WHERE aid = :aid;
        17.715645       UPDATE pgbench_tellers SET tbalance = tbalance + :delta WHERE tid = :tid;
        6.222220        UPDATE pgbench_branches SET bbalance = bbalance + :delta WHERE bid = :bid;
        0.294592        INSERT INTO pgbench_history (tid, bid, aid, delta, mtime) VALUES (:tid, :bid, :aid, :delta, CURRENT_TIMESTAMP);
        0.502843        END;

pg_stat_statements 
Example 1
query               | UPDATE pgbench_accounts SET abalance = abalance + ? WHERE aid = ?;
calls               | 118804
total_time          | 5944.19700000145
min_time            | 0.017
max_time            | 146.501
mean_time           | 0.0500336436483624
stddev_time         | 0.860838186600729
rows                | 118804
Example 2
query               | INSERT INTO pgbench_history (tid, bid, aid, delta, mtime) VALUES (?, ?, ?, ?, CURRENT_TIMESTAMP);
calls               | 118804
total_time          | 16533.2040000006
min_time            | 0.075
max_time            | 1.583
mean_time           | 0.139163698191979
stddev_time         | 0.0342061695940176
rows                | 118804
 
Could anybody explain why results are different? Where is an inaccuracy - in pg_stat_statements or pgbench?

Thanks in advance.


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