HIVE-28622: Duplicate Entries in TXN_WRITE_NOTIFICATION_LOG Due to Oracle's Handling of Empty Strings #5617
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…acle's Handling of Empty Strings
In Oracle, empty strings ('') are treated as NULL values for VARCHAR2 and CHAR data types. This behavior is unique to Oracle and can be confusing, as an empty string is typically considered distinct from NULL in other databases.
As a result, the TXN_WRITE_NOTIFICATION_LOG table receives duplicate entries for a single Hive ACID transaction involving MERGE statements.
This discrepancy leads to issues: the _files and _dumpmetadata files in a Hive ACID incremental dump will not align if the dump scope includes one or more MERGE statements. Consequently, the Hive ACID incremental LOAD fails at the target (DR), blocking subsequent replication executions.
Solution
* Add additional check for partition being null
Testing:
* Tested on cluster with oracle and mysql as backend database
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+1. Looks good to me. |
pudidic
approved these changes
Jan 22, 2025
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In Oracle, empty strings ('') are treated as NULL values for VARCHAR2 and CHAR data types. This behavior is unique to Oracle and can be confusing, as an empty string is typically considered distinct from NULL in other databases.
As a result, the TXN_WRITE_NOTIFICATION_LOG table receives duplicate entries for a single Hive ACID transaction involving MERGE statements.
This discrepancy leads to issues: the _files and _dumpmetadata files in a Hive ACID incremental dump will not align if the dump scope includes one or more MERGE statements. Consequently, the Hive ACID incremental LOAD fails at the target (DR), blocking subsequent replication executions.
Solution
Testing:
What changes were proposed in this pull request?
Why are the changes needed?
Does this PR introduce any user-facing change?
Is the change a dependency upgrade?
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