jackjlli opened a new pull request #6479:
URL: https://github.com/apache/incubator-pinot/pull/6479
## Description
Currently when generating an offline segment, raw data has to be traversed
two times; one time for gathering stats in
`RecordReaderSegmentCreationDataSource`, another time for ingesting actual data.
In this PR, we introduce a new way of ingesting offline data by traversing
the raw data only once. Similarly to mutable realtime segment, a simplified
class called `IntermediateSegment` will be initialized to gather all the data
into dictionary and forwarded index. After all the records are ingested,
`IntermediateSegmentRecordReader` will be passed into
`SegmentIndexCreationDriver` with `SegmentGeneratorConfig`, and the final
offline segment will be built like this:
```
// Build the segment from intermediate segment.
SegmentIndexCreationDriverImpl driver = new
SegmentIndexCreationDriverImpl();
driver.init(segmentGeneratorConfig, intermediateSegmentRecordReader);
driver.build();
```
This mechanism helps greatly reduce the memory pressure in some environment.
E.g. if pinot segments need to be generated directly from spark executors when
data is loaded as iterator, the raw data doesn't have to load into memory two
times.
## Upgrade Notes
Does this PR prevent a zero down-time upgrade? (Assume upgrade order:
Controller, Broker, Server, Minion)
* [ ] Yes (Please label as **<code>backward-incompat</code>**, and complete
the section below on Release Notes)
Does this PR fix a zero-downtime upgrade introduced earlier?
* [ ] Yes (Please label this as **<code>backward-incompat</code>**, and
complete the section below on Release Notes)
Does this PR otherwise need attention when creating release notes? Things to
consider:
- New configuration options
- Deprecation of configurations
- Signature changes to public methods/interfaces
- New plugins added or old plugins removed
* [ ] Yes (Please label this PR as **<code>release-notes</code>** and
complete the section on Release Notes)
## Release Notes
If you have tagged this as either backward-incompat or release-notes,
you MUST add text here that you would like to see appear in release notes of
the
next release.
If you have a series of commits adding or enabling a feature, then
add this section only in final commit that marks the feature completed.
Refer to earlier release notes to see examples of text
## Documentation
If you have introduced a new feature or configuration, please add it to the
documentation as well.
See
https://docs.pinot.apache.org/developers/developers-and-contributors/update-document
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