Hi, I'm currently working on bug#337038 (decimal truncation should be an error, not warning) and am looking for some input on an issue I'm having. Basically, I have a fix implemented but it changes the expected behavior in a number of test cases. The basic question I have at the moment is whether an error should be thrown when a temporary table is created where a decimal value is truncated? I'll expand on the question a little bit below but that's basically what I'm looking for input on.
For example, if I create a table as follows (based on a test case in func_group.test): drizzle> create table t1 (a int, b int, c int); and then insert some values which look like: drizzle> select * from t1; +------+------+------+ | a | b | c | +------+------+------+ | 1 | 1 | 1 | | 1 | 1 | 2 | | 1 | 1 | 3 | | 1 | 1 | 3 | +------+------+------+ 4 rows in set (0.00 sec) Now, if I execute a query with a group by where I group by a fraction as follows (this is the current behavior in trunk): drizzle> select b/c as v, count(*) from t1 group by v; +--------+----------+ | v | count(*) | +--------+----------+ | 0.3333 | 2 | | 0.5000 | 1 | | 1.0000 | 1 | +--------+----------+ 3 rows in set (0.01 sec) drizzle> we can see that a decimal value has been truncated in a temporary table (1/3 has been truncated to 0.3333). Now with the fix I've implemented, when a decimal is truncated, an error occurs when the store_value() method in decimal.cc is executed but in the case of temporary tables when results are recorded in a temporary table, the result value is never checked (it should be checked in the copy_funcs() method in sql_select.cc). Therefore, an error is not issued which results in behavior like so (with the same table definition and data as above): drizzle> select b/c as v, count(*) from t1 group by v; +-----------------+----------+ | v | count(*) | +-----------------+----------+ | 0.5000 | 1 | | 1.0000 | 1 | | 9999999999.9999 | 2 | +-----------------+----------+ 3 rows in set (0.00 sec) drizzle> If an error was thrown, this statement would not execute. Instead, an error would be returned to the user indicating that truncation of a decimal value occurred. My question for the list is whether we should throw an error when creating a temporary table where a decimal value is truncated? -Padraig _______________________________________________ Mailing list: https://launchpad.net/~drizzle-discuss Post to : [email protected] Unsubscribe : https://launchpad.net/~drizzle-discuss More help : https://help.launchpad.net/ListHelp
