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https://issues.apache.org/jira/browse/TRAFODION-40?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14646335#comment-14646335
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ASF GitHub Bot commented on TRAFODION-40:
-----------------------------------------
GitHub user zellerh opened a pull request:
https://github.com/apache/incubator-trafodion/pull/34
TRAFODION-40 Make index-maintenance delete conditional
This fixes the issue where we update an indexed column to itself, and
the index maintenance tree both deletes and re-inserts the index row
within the same millisecond. This makes the index row disappear, as the
delete takes precedence over the insert, even though it happened earlier.
As a side-effect, index maintenance may get faster, because we are
also replacing the CheckAndPut of the index insert with a Put.
We could further improve this by processing multiple Puts together.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/zellerh/incubator-trafodion bug/udf1
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/incubator-trafodion/pull/34.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #34
----
commit 7801e6a200ebef7b0794d4749c38b73c14b28be6
Author: Hans Zeller <[email protected]>
Date: 2015-07-29T16:06:06Z
TRAFODION-40 Make index-maintenance delete conditional
This fixes the issue where we update an indexed column to itself, and
the index maintenance tree both deletes and re-inserts the index row
within the same millisecond. This makes the index row disappear, as the
delete takes precedence over the insert, even though it happened earlier.
As a side-effect, index maintenance may get faster, because we are
also replacing the CheckAndPut of the index insert with a Put.
We could further improve this by processing multiple Puts together.
----
> Compiler work to allow a conditional delete
> -------------------------------------------
>
> Key: TRAFODION-40
> URL: https://issues.apache.org/jira/browse/TRAFODION-40
> Project: Apache Trafodion
> Issue Type: Sub-task
> Reporter: Hans Zeller
>
> Part of TRAFODION-14.
> Selva and Suresh found that we sometimes miss index rows. This is causes if
> all of the following happen: a) we perform index maintenance for an update
> (delete of the old index row, followed by insert of the new row), b) the old
> and new row of the index have the same row key, i.e. we didn't change the
> column values in the index and c) the HBase timestamp is the same for the
> index delete and the update (delete and insert happen in the same
> millisecond).
> Selva suggested to solutions:
> 1. Determine the max. timestamp of the old row and use that timestamp for the
> delete. That would work (unlikely someone did an insert in a different
> statement in the same millisecond), but it would require reading the value
> before an index delete.
> 2. Add a new expression for the index delete (could also do it for the
> insert) that skips the delete if old and new index values match.
> We want to go with solution 2., since it has the better performance. I'm
> filing this JIRA for the necessary compiler work,
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