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https://issues.apache.org/jira/browse/IGNITE-19395?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17873900#comment-17873900
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Aleksandr Polovtsev commented on IGNITE-19395:
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Benchmarking results:
Throughput mode (first measurements are for the {{main}} branch):
{noformat}
Benchmark Mode Cnt Score Error Units
CommitManyWritesBenchmark.commitManyWrites thrpt 25 1.563 ± 0.237 ops/s
Benchmark Mode Cnt Score Error Units
CommitManyWritesBenchmark.commitManyWrites thrpt 25 0.897 ± 0.144 ops/s
{noformat}
> Reduce write amplification for RocksDB partition storage
> --------------------------------------------------------
>
> Key: IGNITE-19395
> URL: https://issues.apache.org/jira/browse/IGNITE-19395
> Project: Ignite
> Issue Type: Improvement
> Reporter: Ivan Bessonov
> Assignee: Aleksandr Polovtsev
> Priority: Major
> Labels: ignite-3
> Time Spent: 10m
> Remaining Estimate: 0h
>
> Currently, the "commit" operation in rocksdb storage looks like this:
> {code:java}
> val data = db.read(writeIntentKey);
> db.remove(writeIntentKey);
> db.write(committedKey, data);{code}
> This is wasteful, we end up writing everything twice. There's another
> solution, we may add a level of indirection to the data:
> {code:java}
> // RowId index.
> [ TableId?? | PartId | RowId | Timestamp ] -> [ DataId ]
> [ TableId?? | PartId | RowId ] -> [ DataId | TxId | CommitTableId |
> CommitPartId ]
> // Data.
> [ DataId ] -> [ Payload ]{code}
> {{DataId}} must be unique. I don't like the idea of auto-incrementing key (we
> should always persist latest value), there must be another way.
> The main idea is that DataId doesn't change while committing the data,
> meaning that it can be generated using RowId and TxId.
> For example, {{RowId ++ beginTimestamp(TxId)}} seems like a unique value
> (with mandatory partition ID prefix and probably a table ID prefix)
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