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https://issues.apache.org/jira/browse/PHOENIX-4579?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16409992#comment-16409992
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ASF GitHub Bot commented on PHOENIX-4579:
-----------------------------------------

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

    https://github.com/apache/phoenix/pull/295#discussion_r176506809
  
    --- Diff: 
phoenix-core/src/main/java/org/apache/phoenix/query/ConnectionQueryServicesImpl.java
 ---
    @@ -2405,16 +2413,26 @@ public Void call() throws Exception {
                                 openConnection();
                                 hConnectionEstablished = true;
                                 boolean isDoNotUpgradePropSet = 
UpgradeUtil.isNoUpgradeSet(props);
    +                            boolean doesSystemCatalogAlreadyExist = false;
    --- End diff --
    
    The flow of this code is very confusing. Let's do the compatibility check 
only once in ensureTableCreated by making the following changes:
    - do not call ensureTableCreated from createTable if the table is a system 
table
    - call ensureTableCreated instead here and remove this entire try block
    - do all checks required in ensureTableCreated where we already determine 
if the table exists or not
    - in ensureTableCreated, if SYSTEM.CATALOG doesn't exist and 
!isAutoUpgradeEnabled or isDoNotUpgradePropSet, then throw our standard 
UpgradeRequiredException immediately without creating system catalog metadata.
    - the only call to checkClientServerCompatibility should be in 
ensureTableCreated (when isMetaTable is true)
    - make sure to be defensive in the creation of the SYSTEM namespace and 
moving of SYSTEM tables as it's possible that multiple clients may be 
attempting to do that.
    
    I think this improve the maintainability of this code (and fix this issue 
too).


> Add a config to conditionally create Phoenix meta tables on first client 
> connection
> -----------------------------------------------------------------------------------
>
>                 Key: PHOENIX-4579
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-4579
>             Project: Phoenix
>          Issue Type: New Feature
>            Reporter: Mujtaba Chohan
>            Assignee: Chinmay Kulkarni
>            Priority: Major
>         Attachments: PHOENIX-4579.patch
>
>
> Currently we create/modify Phoenix meta tables on first client connection. 
> Adding a property to make it configurable (with default true as it is 
> currently implemented).
> With this property set to false, it will avoid lockstep upgrade requirement 
> for all clients when changing meta properties using PHOENIX-4575 as this 
> property can be flipped back on once all the clients are upgraded.



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