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Posted to issues@beam.apache.org by "ASF GitHub Bot (Jira)" <ji...@apache.org> on 2022/04/01 14:37:00 UTC
[jira] [Work logged] (BEAM-14166) Improvements to RowWithGetter
[ https://issues.apache.org/jira/browse/BEAM-14166?focusedWorklogId=751592&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-751592 ]
ASF GitHub Bot logged work on BEAM-14166:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 01/Apr/22 14:36
Start Date: 01/Apr/22 14:36
Worklog Time Spent: 10m
Work Description: mosche commented on pull request #17172:
URL: https://github.com/apache/beam/pull/17172#issuecomment-1085981280
I've drilled down into this a bit and I think I've got some interesting finding's to share @reuvenlax & @TheNeuralBit.
Investigating a few approaches, I would to suggest to push field type based logic in `RowWithGetters` down into `FieldValueGetter`s to remove any branching and allow for better inlining, see [code & benchmark](https://github.com/apache/beam/compare/master...mosche:RowWithGetters-JMH-Getters-LogicPushDown).
I also looked a bit into costs of caching, the picture isn't as clear there. The costs of initializing any data structure facilitating a cache is certainly high compared to the costs of calling getters. One finding though was that `TreeMap` didn't perform any worse than `HashMap`. Given the much lower memory footprint that might be a good pick then. Also, using [materialized Pojo lists](https://github.com/mosche/beam/blob/RowWithGetters-JMH-Getters-LogicPushDown/sdks/java/core/src/main/java/org/apache/beam/sdk/schemas/GetterBasedSchemaProvider.java#L178-L180) helped to improve the performance gain from caching (compared to lazy transforms using `Lists.transform`).
On the other hand, I'm not sure what the original motivation for adding a field value cache in `RowWithGetters` was. Is it just about performance?
Some visualizations for a few selected runs:
- [master vs suggested approach (no caching)](https://jmh.morethan.io/?sources=https://raw.githubusercontent.com/mosche/beam/RowWithGetters-JMH-Getters-LogicPushDown/sdks/java/harness/jmh/jmh-master-cache-disabled.json,https://raw.githubusercontent.com/mosche/beam/RowWithGetters-JMH-Getters-LogicPushDown/sdks/java/harness/jmh/jmh-pr-getters-cache-disabled.json)
- [master vs suggested approach (with caching)](https://jmh.morethan.io/?sources=https://raw.githubusercontent.com/mosche/beam/RowWithGetters-JMH-Getters-LogicPushDown/sdks/java/harness/jmh/jmh-master-cache-HashMaps.json,https://raw.githubusercontent.com/mosche/beam/RowWithGetters-JMH-Getters-LogicPushDown/sdks/java/harness/jmh/jmh-pr-getters-cache-TreeMap-lazy-lists.json)
- [costs of caching (master)](https://jmh.morethan.io/?sources=https://raw.githubusercontent.com/mosche/beam/RowWithGetters-JMH-Getters-LogicPushDown/sdks/java/harness/jmh/jmh-master-cache-disabled.json,https://raw.githubusercontent.com/mosche/beam/RowWithGetters-JMH-Getters-LogicPushDown/sdks/java/harness/jmh/jmh-master-cache-HashMaps.json)
- [costs of caching (suggested approach, treemap)](https://jmh.morethan.io/?sources=https://raw.githubusercontent.com/mosche/beam/RowWithGetters-JMH-Getters-LogicPushDown/sdks/java/harness/jmh/jmh-pr-getters-cache-disabled.json,https://raw.githubusercontent.com/mosche/beam/RowWithGetters-JMH-Getters-LogicPushDown/sdks/java/harness/jmh/jmh-pr-getters-cache-TreeMap-lazy-lists.json)
- [costs of caching (suggested approach, hashmap)](https://jmh.morethan.io/?sources=https://raw.githubusercontent.com/mosche/beam/RowWithGetters-JMH-Getters-LogicPushDown/sdks/java/harness/jmh/jmh-pr-getters-cache-disabled.json,https://raw.githubusercontent.com/mosche/beam/RowWithGetters-JMH-Getters-LogicPushDown/sdks/java/harness/jmh/jmh-pr-getters-cache-HashMap-lazy-lists.json)
- [hashmap vs treemap if using materialized rather than lazy Pojo collections](https://jmh.morethan.io/?sources=https://raw.githubusercontent.com/mosche/beam/RowWithGetters-JMH-Getters-LogicPushDown/sdks/java/harness/jmh/jmh-pr-getters-cache-HashMap-persisted-pojolists.json,https://raw.githubusercontent.com/mosche/beam/RowWithGetters-JMH-Getters-LogicPushDown/sdks/java/harness/jmh/jmh-pr-getters-cache-TreeMap-persisted-pojolists.json)
[](https://jmh.morethan.io/?sources=https://raw.githubusercontent.com/mosche/beam/RowWithGetters-JMH-Getters-LogicPushDown/sdks/java/harness/jmh/jmh-master-cache-HashMaps.json,https://raw.githubusercontent.com/mosche/beam/RowWithGetters-JMH-Getters-LogicPushDown/sdks/java/harness/jmh/jmh-pr-getters-cache-TreeMap-lazy-lists.json)
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Issue Time Tracking
-------------------
Worklog Id: (was: 751592)
Time Spent: 1h 20m (was: 1h 10m)
> Improvements to RowWithGetter
> -----------------------------
>
> Key: BEAM-14166
> URL: https://issues.apache.org/jira/browse/BEAM-14166
> Project: Beam
> Issue Type: Improvement
> Components: sdk-java-core
> Reporter: Moritz Mack
> Assignee: Moritz Mack
> Priority: P2
> Time Spent: 1h 20m
> Remaining Estimate: 0h
>
> Various improvements to getValue(fieldIdx) in RowWithGetters mentioned [here|[https://github.com/apache/beam/pull/16947#discussion_r833602836]:]
> * Minimize memory overhead of cache using either a index lookup (array) or a single hash map if number of fields exceeds the initial hashmap capacity
> * The cache should be checked before calling a getter to avoid any potentially unnecessary conversion in the getter itself.
> * [Nested rows|https://github.com/apache/beam/blob/master/sdks/java/core/src/main/java/org/apache/beam/sdk/values/RowWithGetters.java#L111] should be cached, otherwise the cache of such nested rows can't be leveraged.
> * Handling of collections / maps / iterables can be significantly improved by simply skipping the transform in all cases where {{getValue}} for members is the [identity transform|https://github.com/apache/beam/blob/master/sdks/java/core/src/main/java/org/apache/beam/sdk/values/RowWithGetters.java#L142].
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