Add type: DOUBLE (float8)

.gitignore

@@ -14,3 +14,4 @@ coverage.xml
 .vscode
 results.xml
 venv
+.venv

duckdb_engine/datatypes.py

@@ -11,6 +11,7 @@
 from typing import Any, Callable, Dict, Optional, Type
 
 import duckdb
+import sqlalchemy
 from packaging.version import Version
 from sqlalchemy import exc
 from sqlalchemy.dialects.postgresql.base import PGIdentifierPreparer, PGTypeCompiler
@@ -26,8 +27,10 @@
 (BigInteger, SmallInteger)  # pure reexport
 
 duckdb_version = duckdb.__version__
+sqlalchemy_version = sqlalchemy.__version__
 
 IS_GT_1 = Version(duckdb_version) > Version("1.0.0")
+IS_SQLA_GT_2 = Version(sqlalchemy_version) > Version("2.0.0")
 
 
 class UInt64(Integer):
@@ -206,7 +209,6 @@ def __init__(self, fields: Dict[str, TV]):
     "timetz": sqltypes.TIME,
     "timestamptz": sqltypes.TIMESTAMP,
     "float4": sqltypes.FLOAT,
-    "float8": sqltypes.FLOAT,
     "usmallint": USmallInteger,
     "uinteger": UInteger,
     "ubigint": UBigInteger,
@@ -219,6 +221,9 @@ def __init__(self, fields: Dict[str, TV]):
 }
 if IS_GT_1:
     ISCHEMA_NAMES["varint"] = VarInt
+if IS_SQLA_GT_2:
+    ISCHEMA_NAMES["float8"] = sqltypes.DOUBLE  # type: ignore[attr-defined]
+    ISCHEMA_NAMES["double"] = sqltypes.DOUBLE  # type: ignore[attr-defined]
 
 
 def register_extension_types() -> None:

duckdb_engine/tests/test_datatypes.py

@@ -167,6 +167,26 @@ def test_double_in_sqla_v2(engine: Engine) -> None:
         con.execute(t.select())
 
 
+def test_double(engine: Engine, session: Session) -> None:
+    sqlalchemy = importorskip("sqlalchemy", "2.0.0")
+    base = declarative_base()
+
+    class Entry(base):
+        __tablename__ = "test_double"
+
+        id = Column(Integer, primary_key=True, default=0)
+        value = Column(sqlalchemy.DOUBLE, nullable=False)
+
+    base.metadata.create_all(bind=engine)
+
+    session.add(Entry(value=42.000001))  # type: ignore[call-arg]
+    session.commit()
+
+    result = session.query(Entry).one()
+
+    assert result.value == 42.000001
+
+
 def test_all_types_reflection(engine: Engine) -> None:
     importorskip("sqlalchemy", "1.4.0")
     importorskip("duckdb", "0.5.1")