Обсуждение: Catching DML exceptions in PL/pgSQL
Hello all,<br /> (and sorry if this has been aswered before)<br /><br /> Take this piece of code for example:<br /> .....................<br/><font face="Courier, Courier">begin<br /> _res.code:=1;<br /> select id into iid from logwhere id=_id;<br /> if not found then begin<br /> _res.msg:=''insert'';<br /> <b>insert into log (log,data) values (_log, _data);<br /> if not found</b> then begin<br /> _res.msg:=_res.msg || '' error'';<br/> _res.code:=-1;<br /> end;<br /> end if;<br /> end;<br /> else begin<br/></font>.....................<br /> The thing is if _data (parameter) is null and table has a (data <> null)check, the insert would fail and abort the function before my "if not found" test.<br /><br /> I'm porting a java app.from mssql to postgresql, and the java code relies on the stored procedure to always return it's status (in _res.codein this case).<br /><br /> Is there anything I can do to make sure the function always returns _res ?<br /> Somethingalong the lines of Oracle's exception handling, or the @@error trick in mssql ?<br /><br /><br /><p> Regards,<br/> --<br /> Radu-Adrian Popescu<br /> CSA, DBA, Developer<br /> Aldratech Ltd.
Dnia 2003-06-17 11:25, Użytkownik Radu-Adrian Popescu napisał: > Hello all, > (and sorry if this has been aswered before) > > Take this piece of code for example: > ..................... > begin > _res.code:=1; > select id into iid from log where id=_id; > if not found then begin > _res.msg:=''insert''; > *insert into log (log, data) values (_log, _data); > if not found* then begin > _res.msg:=_res.msg || '' error''; > _res.code:=-1; > end; > end if; > end; > else begin > ..................... > The thing is if _data (parameter) is null and table has a (data <> null) > check, the insert would fail and abort the function before my "if not > found" test. > > I'm porting a java app. from mssql to postgresql, and the java code > relies on the stored procedure to always return it's status (in > _res.code in this case). > > Is there anything I can do to make sure the function always returns _res ? > Something along the lines of Oracle's exception handling, or the @@error > trick in mssql ? You can't do it this way. Your insert is violation of some constraint (problably "not null" or "primary key" constraint). This kind of violation raises exception and whole transaction is aborted. I don't use java, but C librares raises also ordinary C exception which can be easily caught. If you want to avoid such cases - check your data before inserting them. Regards, Tomasz Myrta
At 6/17/2003 11:44, Tomasz Myrta wrote: >Dnia 2003-06-17 11:25, U¿ytkownik Radu-Adrian Popescu napisa³: > >>Hello all, >>(and sorry if this has been aswered before) >>Take this piece of code for example: >>..................... >>begin >> _res.code:=1; >> select id into iid from log where id=_id; >> if not found then begin >> _res.msg:=''insert''; >> *insert into log (log, data) values (_log, _data); >> if not found* then begin >> _res.msg:=_res.msg || '' error''; >> _res.code:=-1; >> end; >> end if; >> end; >> else begin >>..................... >>The thing is if _data (parameter) is null and table has a (data <> null) >>check, the insert would fail and abort the function before my "if not >>found" test. >>I'm porting a java app. from mssql to postgresql, and the java code >>relies on the stored procedure to always return it's status (in _res.code >>in this case). >>Is there anything I can do to make sure the function always returns _res ? >>Something along the lines of Oracle's exception handling, or the @@error >>trick in mssql ? >You can't do it this way. Your insert is violation of some constraint >(problably "not null" or "primary key" constraint). This kind of violation >raises exception and whole transaction is aborted. I don't use java, but C >librares raises also ordinary C exception which can be easily caught. If >you want to avoid such cases - check your data before inserting them. Thanks, unfortunatelly I knew that... My java/db code currently decides whether the call was successful based on 1) return from stored procedure (currently, to be replaced by select * from function_name(...)) 2) SQLException So basically it would work no probs: i.e. instead of reading a -1 when an error occured, there would be an SQLException caught and the final outcome, either way, would be that the java method would still function properly and let the calling code know whether things went okay or not. However, the point was to be able to deal with these exceptions inside pl/plgsql, as it would bring imho a load more power and fexibility to the db code. For instance, it could choose to log failures to a database table, or choose another execution path and so on. Anyway, thanks for the reply :-) -- Radu-Adrian Popescu CSA, DBA, Developer Aldratech Ltd.
Radu-Adrian Popescu wrote: > ..................... > begin > _res.code:=1; > select id into iid from log where id=_id; > if not found then begin > _res.msg:=''insert''; > *insert into log (log, data) values (_log, _data); > if not found* then begin > _res.msg:=_res.msg || '' error''; > _res.code:=-1; > end; > end if; > end; > else begin > ..................... > The thing is if _data (parameter) is null and table has a (data <> null) check, > the insert would fail and abort the function before my "if not found" test. You could test for _data is null, and if so check attnotnull in pg_attribute. E.g. something like: declare iattnotnull bool [...] begin if _data is null then select into iattnotnull attnotnull from pg_catalog.pg_attribute where attrelid = 'log'::regclassand attname = 'data'; if iattnotnull then _res.code := -1; [...] > Is there anything I can do to make sure the function always returns _res ? > Something along the lines of Oracle's exception handling, or the @@error trick > in mssql ? There is currently no way to "catch" the exception in PL/pgSQL, but maybe the above would work for you. HTH, Joe
Joe, Tomasz, Thanks for the reply. In any event, like I said, my java code should work with the functions as they are now, whether db throws an exception or returns some result. Also, the oracle-like exception handling would be really great and i know i'm looking forward to it ! Maybe in 7.5 ? :-) Cheers, -- Radu-Adrian Popescu CSA, DBA, Developer Aldratech Ltd.
Radu, > In any event, like I said, my java code should work with the functions as > they are now, whether db throws an exception or returns some result. > Also, the oracle-like exception handling would be really great and i know > i'm looking forward to it ! > Maybe in 7.5 ? Unfortunately, we seem to still lack a dedicated PL/pgSQL source developer on the project. Know anybody? -- Josh Berkus Aglio Database Solutions San Francisco
At 6/17/2003 08:33, Josh Berkus wrote: >Radu, > > > In any event, like I said, my java code should work with the functions as > > they are now, whether db throws an exception or returns some result. > > Also, the oracle-like exception handling would be really great and i know > > i'm looking forward to it ! > > Maybe in 7.5 ? > >Unfortunately, we seem to still lack a dedicated PL/pgSQL source developer on >the project. Know anybody? Unfortunatelly yacc and myself are not good friends, at least not yet :-) Aside from that, this is pretty bad news for me :-( PEOPLE HELP OUT PL/pgSQL !!! :-O Cheers, -- Radu-Adrian Popescu CSA, DBA, Developer Aldratech Ltd.