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https://issues.apache.org/jira/browse/PHOENIX-6499?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17653937#comment-17653937
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Gourab Taparia commented on PHOENIX-6499:
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I was trying to see if there is way a straightforward way to check if the
schema hasn't changed across versions for SYS tables - but probably there
isn't. From the code path looks like whenever there is a upgrade in the server
version, the upgrade
path([https://github.com/apache/phoenix/blob/master/phoenix-core/src/main/java/org/apache/phoenix/query/ConnectionQueryServicesImpl.java#L3506])
detects it, and ensures that the SYS tables are updated(via
[upgradeSystemCatalogIfRequired|https://github.com/apache/phoenix/blob/master/phoenix-core/src/main/java/org/apache/phoenix/query/ConnectionQueryServicesImpl.java#L3776]
and
[upgradeOtherSystemTablesIfRequired|https://github.com/apache/phoenix/blob/master/phoenix-core/src/main/java/org/apache/phoenix/query/ConnectionQueryServicesImpl.java#L4276])
to the latest version.
For e.g. a case where a client 4.1 is connecting to 5.2 server, and assume
there have been no changes in SYS table schemas in these 2 versions. Then is
there a way to compare the schemas of the SYS tables across the version
programmatically ? A theoritical approach is to use the versioning done in
HBase, to compare across the table schemas for the given client version and the
current server version - and if this is same - we allow the client to connect.
This should be done for all the SYS tables. However, I am not aware of the
nuanaces of the versioning comparision for schemas, and not sure if that will
pan out.
[~vjasani] [~tkhurana] Reaching out early to discuss approaches on how we can
handle this.
> Allow old client to connect to new server with higher major version than
> client
> -------------------------------------------------------------------------------
>
> Key: PHOENIX-6499
> URL: https://issues.apache.org/jira/browse/PHOENIX-6499
> Project: Phoenix
> Issue Type: Improvement
> Reporter: Viraj Jasani
> Assignee: Gourab Taparia
> Priority: Major
>
> Although we do not allow old client with lower major version to connect to
> new server with higher major version, we should have this check based on
> System table schema. If there is no change in System tables schema b/ major
> versions of old client and new server (e.g 4.16 client and 5.1 server), we
> should let old client connect to new server.
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