Folks, I have an issue I would like to run by you for suggestions.
Right now every time you create an entry, I keep track of tags added/removed and call WeblogManager.updateTagCounts(). At first I was doing most of the math in the code (i.e. pojo.setCount(pojo.getCount()+1);pojo.setLastUsed(new Date())) but I was afraid that this would result in data loss or incorrect data. Now I'm doing most of the math in the db (i.e. update set total = total + 1). The table is (id, websiteid, name, total, lastused) and for each tag name we have 1 row for the whole site (websiteid = NULL) and one for each website that used it. So if two users in separate cluster nodes use the same tag for the first time in the system at the same time we will end up with two rows for that tag with websiteid = NULL. There are a couple of options that I've pondered on: - If we were to hash the websiteid and tag name and use that as the id, the transaction would abort for one of the users because we can't have duplicated primary keys. - We could add constraints to the table to make sure that there are no duplicate pairs (websiteid, name) in the table. But I'm not sure how to do that in Hibernate. Note: both approaches would throw an exception and the user would have to try again. - We could do the extra work and do a sum() on getHotTags()/getTags(). - We could write a task that merges these rows once in a while. I'd like to point out that this case shouldn't really happen too often, but I want to make you aware of and looking for suggestions. At the moment, I'm taking the safe approach of computing a group by name and computing the sum(). Also, when looking for a tag row to update, I'm always picking the latest with the hope of helping leaving one of the duplicates with a low number. In summary, I'm comfortable with the approach I've taken at the moment but welcome suggestions. Regards, -Elias
