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https://issues.apache.org/jira/browse/HBASE-3276?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12936123#action_12936123
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HBase Review Board commented on HBASE-3276:
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Message from: "Pranav Khaitan" <[email protected]>
bq. On 2010-11-26 14:54:45, Ryan Rawson wrote:
bq. > trunk/src/main/java/org/apache/hadoop/hbase/KeyValue.java, line 1373
bq. > <http://review.cloudera.org/r/1252/diff/1/?file=17712#file17712line1373>
bq. >
bq. > what are all the consequences for not sorting by type when using
KVComparator? Does this mean we might create HFiles that not sorted properly,
because the HFile comparator uses the KeyComparator directly with ignoreType =
false.
bq. >
bq. > While in memstore we can rely on memstoreTS to roughly order by
insertion time, and the Put/Delete should probably work in that situation, you
are talking about modifiying a pretty core and important concept in how we sort
things.
bq. >
bq. > There are other ways to reconcile bugs like this, one of them is to
extend the memstoreTS concept into the HFile and use that to reconcile during
reads. There is another JIRA where I proposed this.
bq. >
bq. > If we are talking about 0.92 and beyond I'd prefer building a solid
base rather than dangerous hacks like this. Our unit tests are not extremely
extensive, so while they might pass, that doesnt guarantee lack of bad
behaviour later on.
bq. >
Agree. As I mentioned, this is a major change and more thought needs to be
given to it.
However, to resolve issues like HBASE-3276, we need either such a change or
extend the memstoreTS concept to HFile as you mentioned.
About consequences, I don't see anything negative here. This change only
affects the sorting of keys having same row, col, timestamp. After this change,
all keys with the same row, col, ts will be sorted purely based on the order in
which they were inserted. When a memstore is flushed to HFile, the memstoreTS
takes care of ordering. During compactions, the KeyValueHeap breaks ties by
using the sequence ids of storefiles.
- Pranav
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> delete followed by a put with the same timestamp
> ------------------------------------------------
>
> Key: HBASE-3276
> URL: https://issues.apache.org/jira/browse/HBASE-3276
> Project: HBase
> Issue Type: Bug
> Reporter: Kannan Muthukkaruppan
> Assignee: Kannan Muthukkaruppan
>
> [Note: This issue is relevant only for cases that don't use the default
> "time" based versions, but provide/manage versions explicitly.]
> The fix for HBASE-1485 ensures that if there are multiple puts with the same
> timestamp the later one wins.
> However, if there is a delete for a specific timestamp, then the later put
> doesn't win.
> Say for example the following is the sequence of operations:
> put row/col/v1 - value1
> deleteColumn row/col/v1
> put row/col/v1 - value2
> Without the deleteColumn(), HBASE-1485 ensures that "value2" is the winner.
> However, with the deleteColumn() thrown into the mix, the delete wins, and
> one cannot insert a new value at that version. [The only, unsatisfactory,
> workaround at this point seems to be trigger a major compaction. The major
> compact would clear the delete marker, and allow new cells to be created with
> that version again.]
> ---
> Seems like it might not be too complicated to extend the fix for HBASE-1485
> to also respect ordering between delete/put operations. I'll look into this
> further.
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