DuckDB 1.5.6 Fixes Silent Wrong-Result Bugs in UNION ALL and Integer Literals

DuckDB released v1.5.6 on September 28, 2026, the sixth patch in the 1.5 'Variegata' line, and the notable fixes aren't crashes but silent correctness bugs that could return wrong data without any error. These include common subplan elimination producing wrong results when UNION ALL arms share a join subtree, silent truncation of very long integer literals into HUGEINT, and several Parquet read/write issues around VARIANT shredding and TIME_NS values.

• Fix for wrong results from common subplan elimination when UNION ALL arms share a join subtree (#25831)
• Silent truncation of very long integer literals into HUGEINT patched (#25714)
• Parquet VARIANT shredding corrected for REQUIRED fields and element groups (#26162), plus a TIME_NS read/write fix (#25728)
• Caveat: the only sources are DuckDB's own GitHub release notes and blog post, so there's no independent confirmation of how widely these correctness bugs were triggered in practice
• Additional fixes cover UNNEST pushdown, LIMIT pushdown through volatile projections, and max() on Hive partition columns after file pruning

Bottom line If you run DuckDB 1.5.x for analytics or ETL, upgrade to 1.5.6 now since the UNION ALL and integer-literal bugs can return silently wrong results rather than fail loudly.