On Tue, Jun 23, 2009 at 1:12 PM, Mathieu Nebra<mateo21@xxxxxxxxxxxxxx> wrote: > This "flags" table has more or less the following fields: > > UserID - TopicID - LastReadAnswerID We are doing pretty much same thing. > My problem is that everytime a user READS a topic, it UPDATES this flags > table to remember he has read it. This leads to multiple updates at the > same time on the same table, and an update can take a few seconds. This > is not acceptable for my users. First of all, and I'm sure you thought of this, an update isn't needed every time a user reads a topic; only when there are new answers that need to be marked as read. So an "update ... where last_read_answer_id < ?" should avoid the need for an update. (That said, I believe PostgreSQL diffs tuple updates, so in practice PostgreSQL might not be writing anything if you run an "update" with the same value. I will let someone more intimate with the internal details of updates to comment on this.) Secondly, an update should not take "a few seconds". You might want to investigate this part before you turn to further optimizations. In our application we defer the updates to a separate asynchronous process using a simple queue mechanism, but in our case, we found that the updates are fast enough (in the order of a few milliseconds) not to warrant batching them into single transactions. A. -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
