Hi Jingsong, Thanks for clarifying it. Are you suggesting a new method or changing the name of the methods described in the FLIP? Please see my answers and further questions below.
Best regards, Jing On Wed, Jul 20, 2022 at 4:28 AM Jingsong Li <jingsongl...@gmail.com> wrote: > Hi Jing, > > I understand that the statistics for partitions are currently only > used by Hive, so we can look at the Hive implementation: > > See HiveCatalog.getPartitionStatistics. > To get the statistics, we actually get them from the > org.apache.hadoop.hive.metastore.api.Partition object. > Correct. Both new methods will do the same thing but in bulk mode. > > According to HiveMetastore's API, partition-related operations > actually get the partition as well as the statistics information. > I am not really sure which API it is. Methods in HiveMetaStoreClient that are dealing with partitions will either return partitions or statisticObjs, e.g. listPartitions(...) or getPartitionColumnStatistics(...) > > So if the current partition statistics are just for Hive, can we > consider unifying it with Hive? > Yes, we are on the same page. This FLIP is trying to unify it with HiveMetaStoreClient. > > For example, in PushPartitionIntoTableSourceScanRule, just use > `listPartitionWithStats`, and adjust table statistics from partitions. > Does the bulkGetPartitionStatistics work in this case too? Or, do you mean you need both partitions and related statistics returned by a new method called `listPartitionWithStats`? > Best, > Jingsong > > On Tue, Jul 19, 2022 at 8:44 PM Jing Ge <j...@ververica.com> wrote: > > > > Thanks Jingsong for the suggestion. > > > > Do you mean using a different naming convention? There is a thought and > > description in the FLIP about using "list" or "bulkGet": > > > > - bulkGetPartitionStatistics(...) has been chosen over > > listPartitionStatistics(...), because, comparing to database and > partition > > that are static and can be listed, statistics are more dynamic and > will > > need more computation logic to create, therefore using "get" is > > semantically more feasible than list. The "bulk" gives users the hint > that > > this method will work in the bulk mode and return a collection of > instances. > > > > > > As a reference, we can see that no method in MetaStoreClient, that > > calculates statistics, uses the "list" naming convention. > > > > Best regards, > > Jing > > > > On Fri, Jul 15, 2022 at 5:38 AM Jingsong Li <jingsongl...@gmail.com> > wrote: > > > > > Thanks for starting this discussion. > > > > > > Have we considered introducing a listPartitionWithStats() in Catalog? > > > > > > Best, > > > Jingsong > > > > > > On Fri, Jul 15, 2022 at 10:08 AM Jark Wu <imj...@gmail.com> wrote: > > > > > > > > Hi Jing, > > > > > > > > Thanks for starting this discussion. The bulk fetch is a great > > > improvement > > > > for the optimizer. > > > > The FLIP looks good to me. > > > > > > > > Best, > > > > Jark > > > > > > > > On Fri, 8 Jul 2022 at 17:36, Jing Ge <j...@ververica.com> wrote: > > > > > > > > > Hi devs, > > > > > > > > > > After having multiple discussions with Jark and Goldfrey, I'd like > to > > > start > > > > > a discussion on the mailing list w.r.t. FLIP-247[1], which will > > > > > significantly improve the performance by providing the bulk fetch > > > > > capability for table and column statistics. > > > > > > > > > > Currently the statistics information about tables can only be > fetched > > > from > > > > > the catalog by each given partition iteratively. Since getting > > > statistics > > > > > information from catalogs is a very heavy operation, in order to > > > improve > > > > > the query performance, we’d better provide functionality to fetch > the > > > > > statistics information of a table for all given partitions in one > shot. > > > > > > > > > > Based on the manual performance test, for 2000 partitions, the cost > > > will be > > > > > improved from 10s to 2s. The improvement result is 500%. > > > > > > > > > > [1] > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/display/FLINK/FLIP-247%3A+Bulk+fetch+of+table+and+column+statistics+for+given+partitions > > > > > > > > > > Best regards, > > > > > Jing > > > > > > > > >
