On 25 Nov 2012, at 10:46am, Keith Chew <keith.c...@gmail.com> wrote:
> I found that when an update SQL is issued against a table, the WAL file > gets updated with the new record, even though the record is exactly the > same as the current record. > > [snip] > > Is there a specific reason for this? Is there a way to improve this by not > inserting the record into the WAL file if the final record is not changed? I think it would take SQLite a lot of time to read every row to see whether the UPDATE command will change it before generating the new entry. Most people's code wouldn't issue such a command under those circumstances. Richard's suggesting of > UPDATE user SET user_name='Keith' WHERE user_name!='Keith'; is what you're asking for. With that many columns (which is unusual, generally you should be able to keep an entire schema in your head) you can either check them one by one, or concatenate them all together and check to see that the long concatenation hasn't changed: UPDATE user SET a=1,b=2,c=3 WHERE a||b||c!=1||2||3; I seem to remember that this is a database where you have every column, of 40 to 50 columns, indexed. This is also unusual, and not something that SQLite is optimized for, and you're going to get unusual results from it. Simon. _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
