What does timestamp repeating in slow query log mean?

[Joe Murray]

I've got a fairly large application (>1M LoC) with a number of tables with 750k records though the normal implementation would only have 1k - 25k records. There is a cache table that holds text blobs with the keys of these records that are a group cache. I'm trying to figure out what was happening recently when mysqld went crazy/thrashed for a few days. Obviously the truncation of this cache table was taking huge amounts of time. It also appears that by the time it was done truncating it needed to start the truncation again, if I am understanding the repeated timestamp below. Can someone explain to me what it means that these timestamps on different queries are all the same?


# User@Host: thissite[thissite] @ localhost []
# Query_time: 160106.517713 Lock_time: 0.000000 Rows_sent: 0 Rows_examined: 0
SET timestamp=1391090819;
TRUNCATE my_table_cache;
# User@Host: thissite[thissite] @ localhost []
# Query_time: 160126.774491 Lock_time: 0.000000 Rows_sent: 0 Rows_examined: 0
SET timestamp=1391090819;
DELETE g
FROM my_table_cache g
WHERE g.group_id IN ( '205' );
# User@Host: thissite[thissite] @ localhost []
# Query_time: 160329.190431 Lock_time: 0.000000 Rows_sent: 0 Rows_examined: 0
SET timestamp=1391090819;
TRUNCATE my_table_cache;
# User@Host: thissite[thissite] @ localhost []
# Query_time: 160543.276354 Lock_time: 0.000000 Rows_sent: 0 Rows_examined: 0
SET timestamp=1391090819;T
RUNCATE my_table_cache;
# User@Host: thissite[thissite] @ localhost []
# Query_time: 160909.070926 Lock_time: 0.000000 Rows_sent: 0 Rows_examined: 0
SET timestamp=1391090819;
TRUNCATE my_table_cache;
# User@Host: thissite[thissite] @ localhost []
# Query_time: 161107.651733 Lock_time: 0.000000 Rows_sent: 0 Rows_examined: 0
SET timestamp=1391090819;
TRUNCATE my_table_cache;