deprecate Expr::display_name

Ref: apache/datafusion#11797

Author: Michael-J-Ward

python/datafusion/expr.py

@@ -175,7 +175,16 @@ def display_name(self) -> str:
 
         This name will not include any CAST expressions.
         """
-        return self.expr.display_name()
+        import warnings
+        warnings.warn("deprecated since 40.0.0: use schema_name instead", DeprecationWarning)
+        return self.schema_name()
+
+    def schema_name(self) -> str:
+        """Returns the name of this expression as it should appear in a schema.
+
+        This name will not include any CAST expressions.
+        """
+        return self.expr.schema_name()
 
     def canonical_name(self) -> str:
         """Returns a complete string representation of this expression."""

python/datafusion/tests/test_expr.py

@@ -167,3 +167,23 @@ def traverse_logical_plan(plan):
     assert variant.expr().to_variant().qualified_name() == 'table1.name'
     assert str(variant.list()) == '[Expr(Utf8("dfa")), Expr(Utf8("ad")), Expr(Utf8("dfre")), Expr(Utf8("vsa"))]'
     assert not variant.negated()
+
+
+def test_display_name_deprecation():
+    import warnings
+    expr = col("foo")
+    with warnings.catch_warnings(record=True) as w:
+        # Cause all warnings to always be triggered
+        warnings.simplefilter("always")
+
+        # should trigger warning
+        name = expr.display_name()
+
+        # Verify some things
+        assert len(w) == 1
+        assert issubclass(w[-1].category, DeprecationWarning)
+        assert "deprecated" in str(w[-1].message)
+
+    # returns appropriate result
+    assert name == expr.schema_name()
+    assert name == "foo"

src/expr.rs

@@ -187,8 +187,8 @@ impl PyExpr {
 
     /// Returns the name of this expression as it should appear in a schema. This name
     /// will not include any CAST expressions.
-    fn display_name(&self) -> PyResult<String> {
-        Ok(self.expr.display_name()?)
+    fn schema_name(&self) -> PyResult<String> {
+        Ok(format!("{}", self.expr.schema_name()))
     }
 
     /// Returns a full and complete string representation of this expression.