> My question is: when a user submits a new comment, how does the new > "cid" get computed? Do you go through all the existing comments to > determine the highest cid, and then add 1, or is the value cached > somewhere? (Neither the code nor the SQL tables are well documented, so > it's hard to figure this out). Most databases have an AUTO_INCREMENT function, so I imagine that in the table definition, the sql definition of the cid is probably something like cid INT NOT NULL AUTO_INCREMENT the AUTO_INCREMENT is what increases the counter. It is up to the database software to track the counters (not sure how that is done) > > (If possible, point me to the appropriate file/linenumber where this > action takes place). > It is in the definition of the table in the database