Fix: populate PostgresType.oid for array columns to enable binary COPY

[onhate]

Summary

Fixes #431

PostgresType.oid was initialized to 0 and never populated for array child types, causing CopyRequiresText to always fall back to FORMAT TEXT for any table with array columns. This resulted in ~2x slower bulk write throughput.

Root Cause

The check in CopyRequiresText for LIST types:

if (pg_type.children[0].oid != PostgresUtils::ToPostgresOid(child_type)) {
    return true;  // always triggers because oid is always 0
}

Always evaluated as 0 != 1043 → true → FORMAT TEXT because the oid field was never set in either code path.

Changes

1. CreateEmptyPostgresType (DDL-created tables)

When DuckDB creates a table via DDL (e.g. CREATE TABLE ... VARCHAR[]), the child PostgresType.oid was left at 0. Fixed by setting it via ToPostgresOid(), which is correct since DuckDB controls the DDL and the Postgres types will match.

2. TypeToLogicalType (catalog-read tables)

When reading existing Postgres tables from the catalog, the child PostgresType.oid was also never set. Here ToPostgresOid() cannot be used because multiple Postgres type names map to the same DuckDB LogicalType (e.g. both text and varchar map to VARCHAR, but have different OIDs: 25 vs 1043). Added TypeNameToPostgresOid() to resolve the OID from the actual Postgres type name, preserving the text/varchar distinction.

Result

• varchar[] columns now correctly use binary COPY in both paths
• text[] columns correctly fall back to TEXT copy (since TEXTOID != VARCHAROID and the binary writer always emits VARCHAROID)
• Other supported array types (int[], boolean[], uuid[], etc.) also benefit from binary COPY

Test plan

• New test attach_array_binary_copy.test covering 4 scenarios:
  • DDL-created table with VARCHAR[] and INT[]
  • DDL-created table with BOOLEAN[], DATE[], DOUBLE[], UUID[]
  • Existing varchar[] table created via postgres_execute
  • Existing text[] table created via postgres_execute (verifies TEXT fallback still works)
• All existing array and binary copy tests pass

[onhate]

Local test results (macOS ARM64, PostgreSQL 17, DuckDB v1.5.1)

Test	Assertions	Result
attach_array_binary_copy.test (new)	63	✅ Pass
attach_use_binary_copy.test	22	✅ Pass
attach_text_array.test	6	✅ Pass
attach_types.test	401	✅ Pass
attach_types_multidimensional_array.test	66	✅ Pass

No regressions in existing array or binary copy tests.

[staticlibs]

Thanks!

[onhate]

that's cool! thanks @staticlibs