SqlCatalog: namespace_exists matches parent namespaces case-insensitively on SQLite #4163

Apache Iceberg version

main (development)

Please describe the bug 🐞

SqlCatalog.namespace_exists treats a namespace as existing when a child namespace exists, and checks that with LIKE '<namespace>.%'. SQLite evaluates LIKE case-insensitively for ASCII characters, so on SQLite a namespace that differs only in case from the parent of an existing namespace is reported as existing. The exact-match lookups elsewhere in the catalog (==) are case-sensitive, so the catalog ends up inconsistent with itself, and the result differs from PostgreSQL, where LIKE is case-sensitive.

Because create_table, register_table, rename_table, drop_namespace, list_tables, list_namespaces and the namespace property methods all go through namespace_exists, the effects show up across the API:

import tempfile
from pyiceberg.catalog.sql import SqlCatalog
from pyiceberg.schema import Schema
from pyiceberg.types import NestedField, LongType

w = tempfile.mkdtemp()
cat = SqlCatalog("t", uri=f"sqlite:///{w}/c.db", warehouse=f"file://{w}")
cat.create_namespace("sales.eu")

print(cat.namespace_exists("SALES"))  # True, expected False
print(cat.create_table("SALES.orders", schema=Schema(NestedField(1, "id", LongType()))).name())
# ('SALES', 'orders'), expected NoSuchNamespaceError

On a fresh catalog with only sales.eu, cat.create_namespace("SALES") raises NamespaceAlreadyExistsError: Namespace SALES already exists, and cat.load_namespace_properties("SALES") returns {} instead of raising NoSuchNamespaceError.

Expected: namespace_exists("SALES") returns False when only sales / sales.eu exist, matching the case-sensitive exact lookups and the PostgreSQL behaviour. create_table("SALES.orders") raises NoSuchNamespaceError and create_namespace("SALES") succeeds.

Without a nested namespace the check is correct (namespace_exists("SALES") is False when only sales exists), because only the LIKE branch is affected.

Environment: pyiceberg main (0.12.0 dev), SQLAlchemy 2.0.54, SQLite 3.50.4, Python 3.12, macOS arm64.

Willingness to contribute

• I can contribute a fix for this bug independently
• I would be willing to contribute a fix for this bug with guidance from the Iceberg community
• I cannot contribute a fix for this bug at this time