log_statement_stats: What is the significance of values in enclosed in brackets?

Question

I'm reviewing the output of log_statement_stats and would to like to understand the following questions.

1. [0.526408 user 0.112125 sys total] => The previous line already shows CPU seconds of user and system. What is the significance of this line?

2. Every other line as values in brackets. What is the significance of those values in enclosed in brackets?

2016-03-03 10:33:29.259 CET [56868] user@db STATEMENT:  SELECT field1 AS a1, field2 AS a2, field3 AS a3, field4 AS a4, field5 AS a5, field6 AS a6, MSISDN AS a7, field8 AS a8, RETRY_COUNT AS a9 FROM table WHERE ((field3 <= $1) AND (field8 IS NULL)) ORDER BY field3 ASC LIMIT $2 OFFSET $3
2016-03-03 10:33:29.259 CET [56868] user@db LOG:  EXECUTE MESSAGE STATISTICS
2016-03-03 10:33:29.259 CET [56868] user@db DETAIL:  ! system usage stats:
        !       0.000006 elapsed 0.000000 user 0.000000 system sec
        !       [0.526408 user 0.112125 sys total]
        !       0/0 [0/0] filesystem blocks in/out
        !       0/0 [0/1281] page faults/reclaims, 0 [0] swaps
        !       0 [0] signals rcvd, 0/0 [0/0] messages rcvd/sent
        !       0/0 [3516/0] voluntary/involuntary context switches

Thank you

Answer 1

It seems that the values in the brackets refer to the raw usage/stats. Note that the values outside the brackets are adjusted with reference to the last reset (See ResetUsage() above ShowUsage() in the link I shared). The values inside the brackets are the values without that adjustment.

Answer 2

How to verify disk hit by a query

The numbers in square brackets are total for the session so far, the other numbers are deltas between the start and stop of the statement.