fix(oracle): return a sqlglot.DataType, not str, when compiling string dtype (#11124)

Co-authored-by: Phillip Cloud <[email protected]>

Author: NickCrews

ibis/backends/oracle/tests/test_datatypes.py

@@ -1,6 +1,12 @@
 from __future__ import annotations
 
+import pytest
+import sqlglot as sg
+import sqlglot.expressions as sge
+
 import ibis
+import ibis.expr.datatypes as dt
+from ibis.backends.sql.datatypes import OracleType
 
 
 def test_failed_column_inference(con):
@@ -21,3 +27,13 @@ def test_blob_raw(con):
     raw_blob = con.table("blob_raw_blobs_blob_raw")
 
     assert raw_blob.schema() == ibis.Schema(dict(blob="binary", raw="binary"))
+
+
+@pytest.mark.parametrize(
+    ("typ", "length"),
+    [("VARCHAR(4000)", None), ("VARCHAR(3)", 3), ("VARCHAR(4000)", 4000)],
+)
+def test_string(typ, length):
+    expected = sg.parse_one(typ, read="oracle", into=sge.DataType)
+    result = OracleType.from_ibis(dt.String(length=length))
+    assert result == expected

ibis/backends/sql/datatypes.py

@@ -769,8 +769,14 @@ def _from_sqlglot_DECIMAL(
 
     @classmethod
     def _from_ibis_String(cls, dtype: dt.String) -> sge.DataType:
-        nullable = " NOT NULL" if not dtype.nullable else ""
-        return "VARCHAR2(4000)" + nullable
+        expressions = [
+            sge.DataTypeParam(
+                this=sge.convert(dtype.length if dtype.length is not None else 4000)
+            )
+        ]
+        return sge.DataType(
+            this=typecode.VARCHAR, expressions=expressions, is_nested=False
+        )
 
 
 class SnowflakeType(SqlglotType):