PostgreSQL TIMESTAMPTZ schema mismatch: builder lacks timezone

[zfarrell]

Summary

When fetching PostgreSQL TIMESTAMPTZ columns, the Arrow schema declares Timestamp(Microsecond, Some("UTC")) but the actual data is created with Timestamp(Microsecond, None), causing a schema mismatch error.

Root Cause

In src/datafetch/native/postgres.rs:

1. pg_type_to_arrow("timestamptz") correctly returns DataType::Timestamp(Microsecond, Some("UTC"))
2. However, make_builder() at line ~372 creates the builder without timezone info:

   DataType::Timestamp(_, _) => Box::new(TimestampMicrosecondBuilder::with_capacity(capacity)),

The TimestampMicrosecondBuilder creates arrays with None timezone by default.

Fix

Use TimestampMicrosecondBuilder::with_capacity(capacity).with_timezone_opt(tz.clone()) to preserve the timezone from the schema.

Discovered By

Type coverage tests in tests/type_coverage/postgres_types.rs.