Re: [hibernate-dev] Where are the batched fetch statements generated?

fwiw... I have a lot of this implemented locally. At the moment it is "swappable", but I have not yet exposed this as a setting. Also, I only have (1) and (2) implemented. (2) is implemented by padding with the main identifier that triggered the batch load. Plan is to work on (3) tomorrow, if I do not get to it today. https://hibernate.onjira.com/browse/HHH-7746 is the issue I am working for this. On Thu 01 Nov 2012 10:04:03 AM CDT, Steve Ebersole wrote: > > Just to clarify... (3) is not building the entire statement. Most of > the statement can be pre-built. It just needs to append the proper > IN-condition > > On Thu 01 Nov 2012 09:30:41 AM CDT, Steve Ebersole wrote: >> >> Maybe its best to make this configurable too? >> >> I can see 3 selections: >> 1) current algorithm - the current code as is >> 2) current size break down but with padding - the current code except >> selecting the next higher batch size and padding extras (current code >> selects next smaller size, iteratively) >> 3) dynamic - dynamically build the batch statement >> >> wdyt? >> >> On Tue 30 Oct 2012 02:28:31 PM CDT, Steve Ebersole wrote: >>> >>> Well the other option is to not pre-build/cache the statements for the >>> batch sizes. That would free up memory as well as reduce the number >>> of queries to just one, with the offset being the need to build the >>> SQL dynamically (although most of it could be built up front). >>> >>> >>> On 05/08/2012 02:06 AM, Clemens Eisserer wrote: >>>> >>>> Hi Guenther, >>>> >>>>>>> Is it possible to disable prepared statement caching for batched >>>>>>> fetching, so I end up with a single query in the < >>>>>>> default_batch_fetch_size case only >>instead of the >>>>>>> fixed-size batch loading hibernate does by default? >>>> >>>> >>>>> I think the main reason for no feedback so far, is that nobody was >>>>> able to understand this sentence. >>>>> Usually 'prepared statement caching' is a synonym to 'prepared >>>>> statement pooling' and is something which has to be provided by a >>>>> connection-pool (or a jdbc-driver) and thus >>>>> Hibernate does actually not implement any prepared statement >>>>> cache/pooling. >>>>> Can you please explain what you intend under 'prepared statement >>>>> caching'? >>>>> Can you also please try to better explain the second part of your >>>>> sentence? >>>> >>>> >>>> Sorry for beeing that cryptic, I will try to rephrase it: >>>> >>>> When Hibernate does batch-fetching, it generates PreparedStatements >>>> for certain batch sizes - for a batch_size of 50, the prepared >>>> statements for batch-sizes will have the following sizes: >>>> [1,2,3,4,5,6,7,8,9,10,12,25,50]. When e.g. a batch of size 13 should >>>> be fetched, because of the fixed size of the prepared statements, 3 >>>> queries are issued for batch-fetching, although 13 <= 50. In this case >>>> the 3 batches would be of the size 13 = 8 + 4 + 1. >>>> In a latency bound (between db and application) environment, this >>>> serverly hampers response time - instead of a single round-trip to do >>>> the batched fetch, Hibernate requires 3. >>>> (subselect can't be used in my case, because my queries are already >>>> rather complex, and the added complexity confuses the DBs query >>>> planner too much) >>>> >>>> What I did in this case (only for integer PKs) is to pad up to the >>>> next batch size with a non-existant PK. >>>> So, for the example mentioned above, I can use the PreparedStatement >>>> with size 25, and insert padding from 14-25, which will make the query >>>> slightly more inefficient but avoid 2 additioan round-trips. >>>> >>>> - Clemens >>>> _______________________________________________ >>>> hibernate-dev mailing list >>>> hibernate-dev(a)lists.jboss.org >>>> https://lists.jboss.org/mailman/listinfo/hibernate-dev >>>> >>> >> >> -- >> steve(a)hibernate.org >> http://hibernate.org > > > -- > steve(a)hibernate.org > http://hibernate.org -- steve(a)hibernate.org http://hibernate.org