insert waiting

Hi,

after some more debugging I found that my application does on average 3
inserts per second. Which is not very fast, but fast enough for now. But
now and then the whole insert proces will be stalled and drop to 0.1
inserts per second. In the output of "ps aux Op" I see postgres in the
state "INSERT WAITING".

I have some other insert/update process running, but not on the same
table. I am absolutely sure, that my insert process is the only one
working on that table.

Can foreign keys block inserts?

TIA

Ulrich