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https://issues.apache.org/jira/browse/HIVE-8485?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14286304#comment-14286304
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Chaoyu Tang commented on HIVE-8485:
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[~sushanth] Thanks for taking care of this. The patch looks good and I thought
of the exactly same implementation as you are having except that I also
considered to enforce hive.metastore.orm.retrieveMapNullsAsEmptyStrings to only
effect when the backend database is Oracle. I was also wondering if there is a
case that the user would really like to use the null or multiple empty space
string (instead of the empty string) as the parameter value, and if these case
are valid.
> 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
> Attachments: HIVE-8485.2.patch, HIVE-8485.patch
>
>
> 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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