fix: give HiveDialect its own colspecs dict

[rusackas]

Summary

HiveDialect never defines its own colspecs, so it inherits sqlalchemy.engine.default.DefaultDialect.colspecs directly -- the exact same dict object, not a copy:

>>> from sqlalchemy.engine.default import DefaultDialect
>>> from pyhive.sqlalchemy_hive import HiveDialect
>>> HiveDialect.colspecs is DefaultDialect.colspecs
True

Every SQLAlchemy built-in dialect (postgresql, mysql, etc.) defines its own colspecs dict, even when there's nothing to override yet, specifically to avoid this. The reason: mutating a dialect's colspecs in place (HiveDialect.colspecs[SomeType] = ...) is a completely normal way to customize how a type renders for one dialect. Without its own dict, that mutation silently corrupts type handling for every other dialect in the process that also hasn't defined its own colspecs -- not just Hive.

This isn't hypothetical. Apache Superset's Databricks engine spec (which subclasses PyHive's HiveDialect for Databricks support) patches HiveDialect.colspecs[types.String] = ... to customize string-type handling. Because of the shared object, that one line broke type compilation for ~38 unrelated third-party dialects loaded in the same process, until Superset worked around it on its own side: apache/superset#44707.

Fix

Give HiveDialect its own (currently empty) colspecs dict, same as every SQLAlchemy built-in dialect does:

colspecs = {}

Verified this fully isolates it with no other behavior change -- colspecs was and remains empty for this dialect; it's just no longer the same object as DefaultDialect's:

>>> HiveDialect.colspecs is DefaultDialect.colspecs
False
>>> HiveDialect.colspecs[str] = 'test'
>>> DefaultDialect.colspecs
{}

Testing

pyhive/tests/test_sqlalchemy_hive.py requires a live Hive server on localhost:10000, which I didn't have available to run the full suite. This change touches only a class-level attribute with no effect on connection or query logic, so I'm confident it's safe, but flagging that I couldn't run the existing integration tests end to end.

🤖 Generated with Claude Code

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