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https://issues.apache.org/jira/browse/GOBBLIN-1126?focusedWorklogId=426741&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-426741
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ASF GitHub Bot logged work on GOBBLIN-1126:
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Author: ASF GitHub Bot
Created on: 23/Apr/20 21:11
Start Date: 23/Apr/20 21:11
Worklog Time Spent: 10m
Work Description: autumnust opened a new pull request #2966:
URL: https://github.com/apache/incubator-gobblin/pull/2966
Dear Gobblin maintainers,
Please accept this PR. I understand that it will not be reviewed until I
have checked off all the steps below!
### JIRA
- https://issues.apache.org/jira/browse/GOBBLIN-1126
### Description
The contribution of this PR contains:
- Refactored `upConvertOrcStruct` which was used specifically for handling
schema evolution. The downside of the original implementation is, it creates
new OrcStruct for each map call which is usually considered as an anti-pattern
in MR execution. The fix makes it possible to reuse the same `OrcStruct` object
by making this method only generating side-effect but return void.
- The refactored `upConvertOrcStruct` can be reused in column projection of
`OrcStruct` so that if we want to have an arbitrary subset of columns to form a
shuffle key (we used to use the whole record for shuffle key which is
unnecessarily burdensome and harm the performance).
- To accommodate with tests I created a bunch of tools in `OrcUtils`:
-- `orcStructFillerWithFixedValue`: Given a schema, generate a `OrcStruct`
with some value. This would be useful to randomly generate some record in
row-manner and we could write them into a ORC file easily.
-- `writableComparableTypeWidening`: The original `upConvertOrcStruct`
cannot handle this. Added for correctness.
-- `createValueRecursively`: The ORC API to create a `OrcStruct`,
`OrcStruct.createValue` has a problem: If there's nested type within a
contain-type like List/MAP, `createValue` call doesn't create any instance
within the container, so that any nested-type information within the
container's element type is lost. It might be worthwhile to contribute this
back to ORC upstream.
The test might be hard to read, but given all the tools mentioned above,
what I really do is mostly following this sequence:
1. create a ORC schema by: `schema =
TypeDescription.createFromString(schemaString);`
2. create a OrcStruct by `orcStruct =
OrcUtils.createValueRecursively(schema)`.
3. Fill in the value by `OrcUtils.orcStructFillerWithFixedValue(orcStruct,
schema, valueForDifferntTypes ...)`
4. Do this for two different schema: writer schema and reader schema with
certain evolution.
5. `upConvertOrcStruct(recordInWriterSchema, recordInReaderSchema,
readerSchema); `
6. Examine if `recordInReaderSchema`'s result is expected.
### Tests
- [ ] My PR adds the following unit tests __OR__ does not need testing for
this extremely good reason:
### Commits
- [ ] My commits all reference JIRA issues in their subject lines, and I
have squashed multiple commits if they address the same issue. In addition, my
commits follow the guidelines from "[How to write a good git commit
message](http://chris.beams.io/posts/git-commit/)":
1. Subject is separated from body by a blank line
2. Subject is limited to 50 characters
3. Subject does not end with a period
4. Subject uses the imperative mood ("add", not "adding")
5. Body wraps at 72 characters
6. Body explains "what" and "why", not "how"
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Issue Time Tracking
-------------------
Worklog Id: (was: 426741)
Remaining Estimate: 0h
Time Spent: 10m
> Supporting Column Projection in OrcStruct in compaction for making shuffle
> key slimmer
> --------------------------------------------------------------------------------------
>
> Key: GOBBLIN-1126
> URL: https://issues.apache.org/jira/browse/GOBBLIN-1126
> Project: Apache Gobblin
> Issue Type: Bug
> Reporter: Lei Sun
> Priority: Major
> Time Spent: 10m
> Remaining Estimate: 0h
>
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