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https://issues.apache.org/jira/browse/HBASE-13408?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Eshcar Hillel updated HBASE-13408:
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Attachment: HBASE-13408-trunk-v09.patch
We attach a new patch which includes the changes required by the recent
discussion.
Specifically, we removed (undo) some of the changes to the HRegion and
FlushPolicy classes. We moved the code for triggering in memory flush into the
compacting memstore implementation.
We excluded two changes:
(1) we did not remove the StoreSegmentScanner tier from the KeyValueScanner
hierarchy as this would result in empty implementation (of the two methods we
define here) in the other 5 concrete classes implementing the KeyValueScanner
interface, which seems unnecessary.
(2) we did not remove the snapshot - this needs to be discussed in a different
Jira; there are pros and cons, and it shouldn’t be decided without thorough
discussion.
> HBase In-Memory Memstore Compaction
> -----------------------------------
>
> Key: HBASE-13408
> URL: https://issues.apache.org/jira/browse/HBASE-13408
> Project: HBase
> Issue Type: New Feature
> Reporter: Eshcar Hillel
> Assignee: Eshcar Hillel
> Fix For: 2.0.0
>
> Attachments: HBASE-13408-trunk-v01.patch,
> HBASE-13408-trunk-v02.patch, HBASE-13408-trunk-v03.patch,
> HBASE-13408-trunk-v04.patch, HBASE-13408-trunk-v05.patch,
> HBASE-13408-trunk-v06.patch, HBASE-13408-trunk-v07.patch,
> HBASE-13408-trunk-v08.patch, HBASE-13408-trunk-v09.patch,
> HBaseIn-MemoryMemstoreCompactionDesignDocument-ver02.pdf,
> HBaseIn-MemoryMemstoreCompactionDesignDocument-ver03.pdf,
> HBaseIn-MemoryMemstoreCompactionDesignDocument.pdf,
> InMemoryMemstoreCompactionEvaluationResults.pdf,
> InMemoryMemstoreCompactionMasterEvaluationResults.pdf,
> InMemoryMemstoreCompactionScansEvaluationResults.pdf,
> StoreSegmentandStoreSegmentScannerClassHierarchies.pdf
>
>
> A store unit holds a column family in a region, where the memstore is its
> in-memory component. The memstore absorbs all updates to the store; from time
> to time these updates are flushed to a file on disk, where they are
> compacted. Unlike disk components, the memstore is not compacted until it is
> written to the filesystem and optionally to block-cache. This may result in
> underutilization of the memory due to duplicate entries per row, for example,
> when hot data is continuously updated.
> Generally, the faster the data is accumulated in memory, more flushes are
> triggered, the data sinks to disk more frequently, slowing down retrieval of
> data, even if very recent.
> In high-churn workloads, compacting the memstore can help maintain the data
> in memory, and thereby speed up data retrieval.
> We suggest a new compacted memstore with the following principles:
> 1. The data is kept in memory for as long as possible
> 2. Memstore data is either compacted or in process of being compacted
> 3. Allow a panic mode, which may interrupt an in-progress compaction and
> force a flush of part of the memstore.
> We suggest applying this optimization only to in-memory column families.
> A design document is attached.
> This feature was previously discussed in HBASE-5311.
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