Yes, I forgot to mention that I could instantiate the connection in the configure() but then I can't close it (as you confirmed) :(
On Mon, Apr 18, 2016 at 9:46 AM, Aljoscha Krettek <aljos...@apache.org> wrote: > 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 > > >> > > > > >>>>> > > >> > > > > >>>>> > > >> > > > > >>>>> > > >> > > > > > > > >> > > > > > > >> > > > > > >> > > > > >> > > > >> > > > > > > > > >
