Take the tour ×  We have a database which stores the
temperatures of 20 thermometer every 7 seconds. We want to
delete all records in the way that every minute holds just one
tempereature instead of 8 which are older than 3 months. I was
planning to do it as follows as discussed in that question here:
1. Select the (relatively few) surviving rows into a temporary
table.   2. Truncate the table.   3. Re-insert the survivors.
But all devices are working without interruption and inserting
values into the DB so I can not Truncate and rename the
temp_tables since the system should be on all the time. Or can
I? If not, do I have to do it by DELETE VACUUM?  By the way we
delete all unnecessary records which are older than 3 months
just once, afterwards we have to repeat this process every month
for the 4.th month previous (I hope that part was clear). If we
repeat this process at the beginning of 05.2013, we have to
delete the unnecessary records of the month 01.2013. How can I
automatize this process? Should I