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Tim Armstrong resolved IMPALA-7360. ----------------------------------- Resolution: Fixed Fix Version/s: Impala 3.1.0 > Avro scanner sometimes skips blocks when skip marker is on HDFS block boundary > ------------------------------------------------------------------------------ > > Key: IMPALA-7360 > URL: https://issues.apache.org/jira/browse/IMPALA-7360 > Project: IMPALA > Issue Type: Bug > Components: Backend > Affects Versions: Impala 2.10.0, Impala 2.11.0, Impala 3.0, Impala 2.12.0 > Reporter: Tim Armstrong > Assignee: Tim Armstrong > Priority: Blocker > Labels: avro, correctness > Fix For: Impala 3.1.0 > > > The Avro changes in IMPALA-3905 introduced a correctness bug. You can hit it > organically if you have a large avro file where the 16 byte sync marker > straddles a block boundary. In that case the block after the sync marker may > not be scanned, resulting in a few records missing. > It's possible to reproduce on our test data by tweaking max_scan_range_length > until you find a value where count(*) returns fewer results. > {code} > [localhost:21000] default> set max_scan_range_length=256k; select count(*) > from tpch_avro_snap.lineitem; > MAX_SCAN_RANGE_LENGTH set to 256k > Query: select count(*) from tpch_avro_snap.lineitem > Query submitted at: 2018-07-26 10:08:21 (Coordinator: > http://tarmstrong-box:25000) > Query progress can be monitored at: > http://tarmstrong-box:25000/query_plan?query_id=5142ec7a702e67ac:b6882a6f00000000 > +----------+ > | count(*) | > +----------+ > | 6001215 | > +----------+ > Fetched 1 row(s) in 6.77s > [localhost:21000] default> set max_scan_range_length=255k; select count(*) > from tpch_avro_snap.lineitem; > MAX_SCAN_RANGE_LENGTH set to 255k > Query: select count(*) from tpch_avro_snap.lineitem > Query submitted at: 2018-07-26 10:08:31 (Coordinator: > http://tarmstrong-box:25000) > Query progress can be monitored at: > http://tarmstrong-box:25000/query_plan?query_id=3d40e63dacaac65b:99d17eaf00000000 > +----------+ > | count(*) | > +----------+ > | 6000679 | > +----------+ > Fetched 1 row(s) in 1.33s > {code} > We do have test coverage in TestScanRangeLengths that exercise the code with > avro blocks straddling scan ranges. However, the necessary condition for this > bug is that the scan range includes a full avro block, followed by a sync > marker on the boundary with the next scan range. We need to add test coverage > for a larger range of values here - larger files and larger scan ranges. -- This message was sent by Atlassian JIRA (v7.6.3#76005) --------------------------------------------------------------------- To unsubscribe, e-mail: issues-all-unsubscr...@impala.apache.org For additional commands, e-mail: issues-all-h...@impala.apache.org