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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-4278) Implement pure client side transactional index maintenance
Date Thu, 08 Feb 2018 01:18:00 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-4278?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16356329#comment-16356329
] 

ASF GitHub Bot commented on PHOENIX-4278:
-----------------------------------------

Github user JamesRTaylor commented on a diff in the pull request:

    https://github.com/apache/phoenix/pull/291#discussion_r166808341
  
    --- Diff: phoenix-core/src/main/java/org/apache/phoenix/query/ConnectionQueryServicesImpl.java
---
    @@ -850,19 +849,12 @@ private void addCoprocessors(byte[] tableName, HTableDescriptor
descriptor, PTab
                         && !SchemaUtil.isMetaTable(tableName)
                         && !SchemaUtil.isStatsTable(tableName)) {
                     if (isTransactional) {
    -                    if (!descriptor.hasCoprocessor(PhoenixTransactionalIndexer.class.getName()))
{
    -                        descriptor.addCoprocessor(PhoenixTransactionalIndexer.class.getName(),
null, priority, null);
    -                    }
    --- End diff --
    
    This handles the case of the creation of new tables, but we'd need to handle the case
of existing tables as well. This is somewhat trickier because ideally we'd want to handle
the case in which the server jar has been upgraded, but the client jar hasn't been. Until
the client is upgraded (in which case index maintenance will occur on the client side), we'd
need to continue performing index maintenance through this coprocessor. The somewhat clunky
way of doing that is to pass the client Phoenix version through the PhoenixIndexMetaData.
This would be somewhat painful.
    
    Since we've labelled transactions as "beta", perhaps we can punt on this. In this case,
we'd require both the client and server jar to be upgraded at the same time (if transactional
tables are already being used). With this approach, we'd want to modify PhoenixTransactionalIndexer
to be an empty class derived still from BaseRegionObserver.


> Implement pure client side transactional index maintenance
> ----------------------------------------------------------
>
>                 Key: PHOENIX-4278
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-4278
>             Project: Phoenix
>          Issue Type: Improvement
>            Reporter: James Taylor
>            Assignee: Ohad Shacham
>            Priority: Major
>
> The index maintenance for transactions follows the same model as non transactional tables
- coprocessor based on data table updates that looks up previous row value to perform maintenance.
This is necessary for non transactional tables to ensure the rows are locked so that a consistent
view may be obtained. However, for transactional tables, the time stamp oracle ensures uniqueness
of time stamps (via transaction IDs) and the filtering handles a scan seeing the "true" last
committed value for a row. Thus, there's no hard dependency to perform this on the server
side.
> Moving the index maintenance to the client side would prevent any RS->RS RPC calls
(which have proved to be troublesome for HBase). It would require returning more data to the
client (i.e. the prior row value), but this seems like a reasonable tradeoff.



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