fix: DuckDB TIMESTAMPTZ and TIMETZ columns displaying as null (#424)

[datlechin]

Summary

• Fix TIMESTAMPTZ and TIMETZ columns showing as null in DuckDB plugin
• Add missing type names: TIMESTAMPTZ, TIMETZ, TIME_NS, UHUGEINT, ARRAY
• Add type-specific fallback extraction when duckdb_value_varchar returns nil
• Re-query with SQL CAST for TZ types where no C API extraction works (DuckDB v1.5.0 limitation)

Root cause

DuckDB v1.5.0 C API duckdb_value_varchar() returns NULL for TIMESTAMPTZ and TIMETZ columns. duckdb_value_is_null() is also unreliable for these types. The deprecated duckdb_column_data() works for TIMESTAMPTZ but not TIMETZ.

Approach

• TIMESTAMPTZ/TIMETZ: Re-execute query with CASE WHEN col IS NULL THEN NULL ELSE CAST(col AS VARCHAR) END for TZ columns, then patch results
• Other fallback types: Type-specific extraction via duckdb_value_timestamp, duckdb_value_int*, etc.
• Missing type names: Added 5 missing DuckDB type constants to typeName(for:)

Closes #424

Test plan

• Build succeeds
• Lint clean (0 violations)
• Manual: DuckDB SELECT '2026-03-22T12:00:00Z'::timestamptz AS tm shows timestamp value
• Manual: DuckDB SELECT '12:00:00+05:30'::timetz AS t shows time with offset
• Manual: NULL TIMESTAMPTZ/TIMETZ values display as NULL (not garbage)
• Manual: Non-TZ types (DATE, TIME, TIMESTAMP, VARCHAR, INTEGER) still work

Summary by CodeRabbit

• Bug Fixes
  • Fixed an issue where certain temporal column types were incorrectly displayed as null values in DuckDB queries. These columns now properly return their actual values.

[coderabbitai]

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: f5371e54-4c96-45b8-a01a-ef2e2e05b596

📥 Commits

Reviewing files that changed from the base of the PR and between 63b8873 and caeaa5d.

📒 Files selected for processing (1)

• Plugins/DuckDBDriverPlugin/DuckDBPlugin.swift

📝 Walkthrough

Walkthrough

The DuckDB plugin was updated to fix temporal columns (TIMESTAMPTZ, TIMETZ, etc.) displaying as null. Changes include post-processing query results with a TZ column patcher, implementing fallback type conversions when varchar extraction fails, and extending type name recognition for additional DuckDB temporal and numeric types.

Changes

Cohort / File(s)	Summary
Documentation CHANGELOG.md	Added fix entry documenting DuckDB update preventing temporal columns from displaying as null.
DuckDB Plugin Core Logic Plugins/DuckDBDriverPlugin/DuckDBPlugin.swift	Implemented post-processing via patchTzColumns to handle TIMESTAMPTZ/TIMETZ columns; enhanced extractResult to track column types and use fallback conversions; extended type name recognition; added helpers for formatted extraction of timestamps, times, booleans, and integers; changed DuckDBRawResult.rows to mutable for in-place patching.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~50 minutes

Poem

🐰 Timestamps were lost in the void so deep,
TZ columns slumbered, null in their sleep,
But now with a patch and conversions so bright,
Temporal values hop back into sight! 🕐✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 10.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title directly summarizes the main fix: addressing TIMESTAMPTZ and TIMETZ columns displaying as null in DuckDB, matching the core objective of the PR.
Linked Issues check	✅ Passed	The PR implements all required fixes: adds missing DuckDB type names, implements fallback type-specific extraction, and patches TZ columns to resolve the null display issue reported in #424.
Out of Scope Changes check	✅ Passed	All changes are directly related to fixing TIMESTAMPTZ/TIMETZ null display: type recognition, fallback extraction, and TZ column patching. No out-of-scope changes detected.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/duckdb-timestamptz-424

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