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https://issues.apache.org/jira/browse/HIVE-8485?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14267083#comment-14267083
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Sushanth Sowmyan commented on HIVE-8485:
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I've done some debugging, and am able to verify the same issue. That said,
since thrift does not support nulls in maps, we should be verifying on our end
that we do not send back nulls in any case. To this end, I have a patch that
does the following:
* Introduces a new HiveConf parameter :
*hive.metastore.orm.retrieveMapNullsAsEmptyStrings* that defaults to *false*
* For operation with oracle, or any other datastore that convers empty
strings to nulls, we'd set this to true, but by default, it'd be false.
* If this parameter is set to true, ObjectStore will transform any null map
values it finds in any of the parameters maps to "".
* If this parameter is set to false, ObjectStore will prune any map entry
where the value is null.
This way, irrespective of whether or not we get nulls back from DN, we
sanity-guard our usage.
> HMS on Oracle incompatibility
> -----------------------------
>
> Key: HIVE-8485
> URL: https://issues.apache.org/jira/browse/HIVE-8485
> Project: Hive
> Issue Type: Bug
> Components: Metastore
> Environment: Oracle as metastore DB
> Reporter: Ryan Pridgeon
> Assignee: Chaoyu Tang
>
> Oracle does not distinguish between empty strings and NULL,which proves
> problematic for DataNucleus.
> In the event a user creates a table with some property stored as an empty
> string the table will no longer be accessible.
> i.e. TBLPROPERTIES ('serialization.null.format'='')
> If they try to select, describe, drop, etc the client prints the following
> exception.
> ERROR ql.Driver: FAILED: SemanticException [Error 10001]: Table not found
> <table name>
> The work around for this was to go into the hive metastore on the Oracle
> database and replace NULL with some other string. Users could then drop the
> tables or alter their data to use the new null format they just set.
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