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Gabor Kaszab commented on IMPALA-8809: -------------------------------------- Did an experiment to figure out a way to reload a subset of the partitions. Apparently querying table or partition data from HMS doesn't provide any fields that detect compactions. There is one option that would provide us a way: HMS has a compactions table that can be queried by show_compat() interface. However, this call gives back the total list of compactions that doesn't seem optimal to query. Anyway after getting the results it's feasible to query for the table name/partition name. So it's feasible, still I'm not comfortable of going this direction as querying that table can be expensive. > Refresh a subset of partitions for ACID tables > ---------------------------------------------- > > Key: IMPALA-8809 > URL: https://issues.apache.org/jira/browse/IMPALA-8809 > Project: IMPALA > Issue Type: Improvement > Affects Versions: Impala 3.3.0 > Reporter: Gabor Kaszab > Assignee: Gabor Kaszab > Priority: Critical > Labels: impala-acid > > Enhancing REFRESH logic to handle ACID tables was covered by this change: > https://issues.apache.org/jira/browse/IMPALA-8600 > Basically each user initiated REFRESH PARTITION is rejected meanwhile the > REFRESH_PARTITION event in event processor are actually doing a full table > load for ACID tables. > There is room for improvement: When a full table refresh is being executed on > an ACID table we can have 2 scenarios: > - If there was some schema changes then reload the full table. Identify such > a scenario should be possible by checking the table-level writeId. However, > there is a bug in Hive that it doesn't update that field for partitioned > tables (https://issues.apache.org/jira/browse/HIVE-22062). This would be the > desired way but could also be workarounded by checking other fields lik > lastDdlChanged or such. > - If a full table refresh is not needed then we should fetch the > partition-level writeIds and reload only the ones that are out-of-date > locally. -- This message was sent by Atlassian Jira (v8.3.4#803005) --------------------------------------------------------------------- To unsubscribe, e-mail: issues-all-unsubscr...@impala.apache.org For additional commands, e-mail: issues-all-h...@impala.apache.org