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https://issues.apache.org/jira/browse/CRUNCH-607?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15266824#comment-15266824
]
Josh Wills commented on CRUNCH-607:
-----------------------------------
+1
> MemGroupedTable - iterator() can only be called once on this Iterable
> ---------------------------------------------------------------------
>
> Key: CRUNCH-607
> URL: https://issues.apache.org/jira/browse/CRUNCH-607
> Project: Crunch
> Issue Type: Bug
> Components: Core
> Affects Versions: 0.8.4
> Reporter: Nathan Schile
> Assignee: Josh Wills
> Attachments: CRUNCH-607.patch
>
>
> From the user mailing list:
> I'm running into a "java.lang.IllegalStateException: iterator() can only be
> called once on this Iterable" [1] when running a unit test that
> utilizes a MemCollection. The pipeline appears to runs fine when running on a
> cluster. I have a PGroupedTable that I am running multiple operations
> (mapValues, ungroup) [2] on that is causing the exception. The mapValues and
> the ungroup operations are run in separate jobs on the cluster, so I don't
> believe I should be running into iterator issues. This constraint was
> introduced by CRUNCH-192 [3].
> Gabriel Reid stated "Looks like the MemPipeline is doing something wrong when
> multiple PCollections are created from a single PCollection." [4]
> [1]
> apache-crunch-0.8.4 branch
> iterator() can only be called once on this Iterable
> java.lang.IllegalStateException: iterator() can only be called once on this
> Iterable
> at
> org.apache.crunch.impl.SingleUseIterable.iterator(SingleUseIterable.java:43)
> at
> org.apache.crunch.impl.mem.collect.MemGroupedTable$UngroupFn.process(MemGroupedTable.java:148)
> at
> org.apache.crunch.impl.mem.collect.MemGroupedTable$UngroupFn.process(MemGroupedTable.java:145)
> at
> org.apache.crunch.impl.mem.collect.MemCollection.parallelDo(MemCollection.java:155)
> at
> org.apache.crunch.impl.mem.collect.MemCollection.parallelDo(MemCollection.java:143)
> at
> org.apache.crunch.impl.mem.collect.MemGroupedTable.ungroup(MemGroupedTable.java:142)
> [2]
> PGroupedTable<String, Item> itemsByPersonId =
> AvroCollections.keyByAvroField(items, "person_id",
> Avros.strings()).groupByKey();
> PTable<String, Long> newestOrderByPersonId =
> itemsByPersonId
> .mapValues("Find latest order for each person", new
> MaxOrderMapFn(), Avros.longs());
> return itemsByPersonId.ungroup().join(newestOrderByPersonId).parallelDo(
> "Filter old items, leaving only current order items",
> new PreviousOrderItemFilter(),
> Avros.tableOf(Avros.strings(), Avros.specifics(Item.class)));
> [3] https://issues.apache.org/jira/browse/CRUNCH-192
> https://github.com/apache/crunch/commit/cbc7c2fb30ad0486e7ec60656c079c81e41eda2c
> [4] http://mail-archives.apache.org/mod_mbox/crunch-user/201604.mbox/date
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