There is also InputFormat.configure() which is called before any split processing happens. But I see your point about a missing close() method that is called after all input splits have been processed.
On Mon, 18 Apr 2016 at 09:44 Stefano Bortoli <s.bort...@gmail.com> wrote: > Of course there is one already. We'll look into the runtime context. > > saluti, > Stefano > > 2016-04-18 9:41 GMT+02:00 Stefano Bortoli <s.bort...@gmail.com>: > > > Being a generic JDBC input format, I would prefer to stay with Row, > > letting the developer manage the cast according to the driver > > functionalities. > > > > As for the open() and close() issue, I agree with Flavio that we'd need a > > better management of the inputformat lifecycle. Perhaps a new interface > > extending it: RichInputFormat? > > > > my2c. > > > > Stefano > > > > 2016-04-18 9:35 GMT+02:00 Flavio Pompermaier <pomperma...@okkam.it>: > > > >> Talking with Stefano this morning and looking at the DataSourceTask code > >> we > >> discovered that the open() and close() methods are both called for every > >> split and not once per inputFormat instance (maybe open and close should > >> be > >> renamed as openSplit and closeSplit to avoid confusion...). > >> I think that it could worth to add 2 methods to the InputFormat (e.g. > >> openInputFormat() and closeInputFormat() ) to allow for the managment of > >> the InputFormat lifecycle, otherwise I'll need to instantiate a pool > (and > >> thus adding a dependency) to avoid the creation of a new connection > >> (expensive operation) for every split (that in our use case happens > >> millions of times). > >> > >> What about the output of the inputFormat? how do you want me to proceed? > >> With POJO or Row? If POJO, which strategy do you suggest? > >> > >> Best, > >> Flavio > >> > >> On Fri, Apr 15, 2016 at 2:06 PM, Stefano Bortoli <s.bort...@gmail.com> > >> wrote: > >> > >> > If we share the connection, then we should also be careful with the > >> close() > >> > implementation. I did not see changes for this method in the PR. > >> > > >> > saluti, > >> > Stefano > >> > > >> > 2016-04-15 11:01 GMT+02:00 Flavio Pompermaier <pomperma...@okkam.it>: > >> > > >> > > Following your suggestions I've fixed the connection reuse in my PR > at > >> > > https://github.com/apache/flink/pull/1885. > >> > > I simply check in the establishConnection() if dbConn!=null and, in > >> that > >> > > case, I simply return immediately. > >> > > > >> > > Thus, the only remaining thin to fix is the null handling. Do you > have > >> > any > >> > > suggestion about how to transform the results in a POJO? > >> > > Maybe returning a Row and then let the user manage the conversion to > >> the > >> > > target POJO in a successive map could be a more general soloution? > >> > > > >> > > Best, > >> > > Flavio > >> > > > >> > > On Thu, Apr 14, 2016 at 6:52 PM, Fabian Hueske <fhue...@gmail.com> > >> > wrote: > >> > > > >> > > > There is an InputFormat object for each parallel task of a > >> DataSource. > >> > > > So for a source with parallelism 8 you will have 8 instances of > the > >> > > > InputFormat running, regardless whether this is on one box with 8 > >> slots > >> > > or > >> > > > 8 machines with 1 slots each. > >> > > > The same is true for all other operators (Map, Reduce, Join, etc.) > >> and > >> > > > DataSinks. > >> > > > > >> > > > Note, a single task does not fill a slot, but a "slice" of the > >> program > >> > > (one > >> > > > parallel task of each operator) fills a slot. > >> > > > > >> > > > Cheers, Fabian > >> > > > > >> > > > 2016-04-14 18:47 GMT+02:00 Flavio Pompermaier < > pomperma...@okkam.it > >> >: > >> > > > > >> > > > > ok thanks!just one last question: an inputformat is instantiated > >> for > >> > > each > >> > > > > task slot or once for task manger? > >> > > > > On 14 Apr 2016 18:07, "Chesnay Schepler" <ches...@apache.org> > >> wrote: > >> > > > > > >> > > > > > no. > >> > > > > > > >> > > > > > if (connection==null) { > >> > > > > > establishCOnnection(); > >> > > > > > } > >> > > > > > > >> > > > > > done. same connection for all splits. > >> > > > > > > >> > > > > > On 14.04.2016 17:59, Flavio Pompermaier wrote: > >> > > > > > > >> > > > > >> I didn't understand what you mean for "it should also be > >> possible > >> > to > >> > > > > reuse > >> > > > > >> the same connection of an InputFormat across InputSplits, > i.e., > >> > > calls > >> > > > of > >> > > > > >> the open() method". > >> > > > > >> At the moment in the open method there's a call to > >> > > > establishConnection, > >> > > > > >> thus, a new connection is created for each split. > >> > > > > >> If I understood correctly, you're suggesting to create a pool > >> in > >> > the > >> > > > > >> inputFormat and simply call poo.borrow() in the open() rather > >> than > >> > > > > >> establishConnection? > >> > > > > >> > >> > > > > >> On 14 Apr 2016 17:28, "Chesnay Schepler" <ches...@apache.org > > > >> > > wrote: > >> > > > > >> > >> > > > > >> On 14.04.2016 17:22, Fabian Hueske wrote: > >> > > > > >>> > >> > > > > >>> Hi Flavio, > >> > > > > >>>> > >> > > > > >>>> that are good questions. > >> > > > > >>>> > >> > > > > >>>> 1) Replacing null values by default values and simply > >> forwarding > >> > > > > records > >> > > > > >>>> is > >> > > > > >>>> very dangerous, in my opinion. > >> > > > > >>>> I see two alternatives: A) we use a data type that > tolerates > >> > null > >> > > > > >>>> values. > >> > > > > >>>> This could be a POJO that the user has to provide or Row. > The > >> > > > drawback > >> > > > > >>>> of > >> > > > > >>>> Row is that it is untyped and not easy to handle. B) We use > >> > Tuple > >> > > > and > >> > > > > >>>> add > >> > > > > >>>> an additional field that holds an Integer which serves as a > >> > bitset > >> > > > to > >> > > > > >>>> mark > >> > > > > >>>> null fields. This would be a pretty low level API though. I > >> am > >> > > > leaning > >> > > > > >>>> towards the user-provided POJO option. > >> > > > > >>>> > >> > > > > >>>> i would also lean towards the POJO option. > >> > > > > >>> > >> > > > > >>> 2) The JDBCInputFormat is located in a dedicated Maven > >> module. I > >> > > > think > >> > > > > we > >> > > > > >>>> can add a dependency to that module. However, it should > also > >> be > >> > > > > possible > >> > > > > >>>> to > >> > > > > >>>> reuse the same connection of an InputFormat across > >> InputSplits, > >> > > > i.e., > >> > > > > >>>> calls > >> > > > > >>>> of the open() method. Wouldn't that be sufficient? > >> > > > > >>>> > >> > > > > >>>> this is the right approach imo. > >> > > > > >>> > >> > > > > >>> Best, Fabian > >> > > > > >>>> > >> > > > > >>>> 2016-04-14 16:59 GMT+02:00 Flavio Pompermaier < > >> > > pomperma...@okkam.it > >> > > > >: > >> > > > > >>>> > >> > > > > >>>> Hi guys, > >> > > > > >>>> > >> > > > > >>>>> I'm integrating the comments of Chesnay to my PR but > >> there's a > >> > > > couple > >> > > > > >>>>> of > >> > > > > >>>>> thing that I'd like to discuss with the core developers. > >> > > > > >>>>> > >> > > > > >>>>> > >> > > > > >>>>> 1. about the JDBC type mapping (addValue() method at > >> [1]: > >> > At > >> > > > the > >> > > > > >>>>> moment > >> > > > > >>>>> if I find a null value for a Double, the getDouble > of > >> > jdbc > >> > > > > return > >> > > > > >>>>> 0.0. > >> > > > > >>>>> Is > >> > > > > >>>>> it really the correct behaviour? Wouldn't be better > to > >> > use a > >> > > > > POJO > >> > > > > >>>>> or > >> > > > > >>>>> the > >> > > > > >>>>> Row of datatable that can handle void? Moreover, the > >> > mapping > >> > > > > >>>>> between > >> > > > > >>>>> SQL > >> > > > > >>>>> type and Java types varies much from the single JDBC > >> > > > > >>>>> implementation. > >> > > > > >>>>> Wouldn't be better to rely on the Java type coming > from > >> > > using > >> > > > > >>>>> resultSet.getObject() to get such a mapping rather > than > >> > > using > >> > > > > the > >> > > > > >>>>> ResultSetMetadata types? > >> > > > > >>>>> 2. I'd like to handle connections very efficiently > >> because > >> > > we > >> > > > > >>>>> have a > >> > > > > >>>>> use > >> > > > > >>>>> case with billions of records and thus millions of > >> splits > >> > > and > >> > > > > >>>>> establish > >> > > > > >>>>> a > >> > > > > >>>>> new connection each time could be expensive. Would it > >> be a > >> > > > > >>>>> problem to > >> > > > > >>>>> add > >> > > > > >>>>> apache pool dependency to the jdbc batch connector in > >> > order > >> > > to > >> > > > > >>>>> reuase > >> > > > > >>>>> the > >> > > > > >>>>> created connections? > >> > > > > >>>>> > >> > > > > >>>>> > >> > > > > >>>>> [1] > >> > > > > >>>>> > >> > > > > >>>>> > >> > > > > >>>>> > >> > > > > >>>>> > >> > > > > > >> > > > > >> > > > >> > > >> > https://github.com/fpompermaier/flink/blob/FLINK-3750/flink-batch-connectors/flink-jdbc/src/main/java/org/apache/flink/api/java/io/jdbc/JDBCInputFormat.java > >> > > > > >>>>> > >> > > > > >>>>> > >> > > > > >>>>> > >> > > > > > > >> > > > > > >> > > > > >> > > > >> > > >> > > > > >
