Hi, I have two tables into which I dump mail statistics. The two tables are:
create table attachments (
create table mail (
The table mail holds information about each mail message. The table attachments holds the name of any attachments. Linking the attachment(s) and the message is the id.
I want to delete all records relating to mail that is over two months old. I tried:
select count(*) from attachments a where a.id in (select m.id from mail m where m.date < now()-62);
but ran out of swap. The mail table is 19Mb, the attachment one 1Mb. I was up to 380Mb of swap used on a machine with 128Mb RAM, and over 15 minutes run time. At that point I killed the query.
I next tried is as follows:
drop table temp;
select id into temp from mail where date < now()-62;
delete from attachments where id in (select id from temp);
delete from mail where date < now()-62;
This worked fine and deleted the records as intended in a few minutes. Can anyone see why the initial query ate so much swap?
pgsql-sql by date
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