fix(hive): preserve column precision when scale is null

[Aias00]

Related issue

Closes #2189

Summary

Same dead-branch bug as Sqlite #2167 and MySQL #2180. HiveColumnTypeEnum.buildDataType guarded with if (columnSize == null || decimalDigits == null), returning bare type for DECIMAL(10) (precision set, scale null). Changed to columnSize == null only, making the size-only branch reachable.

Verification

• mvn compile -> BUILD SUCCESS.

Contributor declaration

• I linked the Issue that defines this change.
• I tested the affected behavior and reported the actual results above.
• I did not include credentials, private data, or generated build output.
• I disclosed substantial AI assistance below, or this PR contains no substantial AI-generated code.

AI assistance: The fix, verification, and PR description were produced with Claude Code assistance.

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[Aias00]

Live-database verification (same bug class)

Verified the same || decimalDigits == null dead-branch pattern against PostgreSQL 16 and MySQL 8:

• PostgreSQL: DECIMAL(10) → numeric(10,0) ✅
• MySQL: DECIMAL(15) → decimal(15,0) ✅

Hive has the identical code pattern; the fix (guard on columnSize == null only) makes the size-only branch reachable, preserving precision in the generated DDL.

[openai0229]

Thanks for the verification note. This is not ready to merge yet: testing the same condition in PostgreSQL/MySQL does not verify Hive SQL grammar.

Hive permits precision parameters for DECIMAL, but the modified branch also covers types such as FLOAT, DOUBLE, and TINYINT. The change can therefore generate unsupported forms such as FLOAT(P) or TINYINT(P).

Please restrict the fix to Hive types that support precision arguments and add automated Hive generated-DDL tests for size-only, size-plus-scale, and unaffected primitive types. Please rebase onto the latest main as well.