HIVE-29554: Refactor MTableColumnStatistics and MPartitionColumnStatistics to avoid code duplication

[thomasrebele]

HIVE-29554

What changes were proposed in this pull request?

Extract a common superclass MColumnStatistics from MPartitionColumnStatistics and MColumnStatistics and combine some methods that use the latter two.

Why are the changes needed?

There is a lot of code duplication around column statistics, which increases the risk of diverging code and partially applied fixes.

Does this PR introduce any user-facing change?

No

How was this patch tested?

1. I've run Hive from the master branch (13f3208), created a table with some values, and executed analyze table tab1 compute statistics for columns;. I verified the statistics with describe formatted tab1 a;.
2. I stopped Hive, and run Hive with the changes of the PR. I checked that the statistics are shown correctly. I inserted more values into the table and executed the ANALYZE TABLE ... command. I verified the statistics.
3. I stopped Hive, and run Hive from the master branch again. I verified the statistics. I inserted more values into the table and executed the ANALYZE TABLE ... command. I verified the statistics.

I started and run the DESCRIBE FORMATTED, ANALYZE TABLE, DESCRIBE FORMATTED sequence for

• a metastore server with the changes from the PR, and
• a hiveserver and beeline from the master branch

and vice versa, i.e.,

• a metastore server from the master branch, and
• a hiveserver and beeline with the changes from the PR

All commands worked as expected.

[sonarqubecloud]

Quality Gate passed

Issues
14 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
1.5% Duplication on New Code

See analysis details on SonarQube Cloud

[thomasrebele]

There are Sonar warnings about the length of the line. The original methods in MPartitionColumnStatistics and MTableColumnStatistics had them as well. In case I make an update to the PR, I'll fix it, otherwise I would just leave that line (and setTimestampStats) as-is.

[thomasrebele]

Sonar warns about the "cognitive complexity" limit. The limit has been exceeded in the original implementation as well. I think refactoring the methods is out-of-scope for this PR, so I'll just leave them as-is.

[Copilot]

Pull request overview

Refactors metastore column-statistics persistence models to remove duplicated fields/methods by introducing a shared MColumnStatistics superclass, and consolidates converter logic to operate on the common base type.

Changes:

• Introduce MColumnStatistics as a shared superclass for table/partition column stats and move common fields/methods there.
• Update JDO metadata to model inheritance and remove duplicated field mappings from the subclasses.
• Consolidate conversion/copy logic in StatObjectConverter and update call sites to use the unified APIs.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
standalone-metastore/metastore-server/src/main/resources/package.jdo	Adds MColumnStatistics JDO class with subclass-table inheritance and removes duplicated field mappings from table/partition stats classes.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/model/MTableColumnStatistics.java	Makes table column stats extend MColumnStatistics, keeping only the table reference.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/model/MPartitionColumnStatistics.java	Makes partition column stats extend MColumnStatistics, keeping only the partition reference.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/model/MColumnStatistics.java	New shared superclass containing the common stats fields and helper setters/getters.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/StatObjectConverter.java	Reuses shared copy/merge logic via MColumnStatistics and unifies get*ColumnStatisticsObj into getColumnStatisticsObj.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/ObjectStore.java	Updates callers to use StatObjectConverter.getColumnStatisticsObj(...) for both table and partition stats.

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