feat(duckdb): implement strftime

ibis/backends/duckdb/registry.py

@@ -146,6 +146,19 @@ def _regex_extract(t, expr):
     return result
 
 
+def _strftime(t, expr):
+    op = expr.op()
+    format_str = op.format_str
+    if not isinstance(format_str_op := format_str.op(), ops.Literal):
+        raise TypeError(
+            "DuckDB format_str must be a literal `str`; "
+            f"got {type(format_str)}"
+        )
+    return sa.func.strftime(
+        t.translate(op.arg), sa.text(repr(format_str_op.value))
+    )
+
+
 operation_registry.update(
     {
         ops.ArrayColumn: _array_column,
@@ -173,6 +186,7 @@ def _regex_extract(t, expr):
             lambda arg: sa.func.approx_quantile(arg, sa.text(str(0.5)))
         ),
         ops.HLLCardinality: reduction(sa.func.approx_count_distinct),
+        ops.Strftime: _strftime,
     }
 )
 

ibis/backends/tests/test_temporal.py

@@ -467,15 +467,40 @@ def test_interval_add_cast_column(backend, alltypes, df):
 
 
 @pytest.mark.parametrize(
-    ('ibis_pattern', 'pandas_pattern'), [('%Y%m%d', '%Y%m%d')]
+    ('expr_fn', 'pandas_pattern'),
+    [
+        param(
+            lambda t: t.timestamp_col.strftime('%Y%m%d').name("formatted"),
+            '%Y%m%d',
+            id="literal_format_str",
+        ),
+        param(
+            lambda t: (
+                t.mutate(suffix="%d")
+                .select(
+                    [
+                        lambda t: t.timestamp_col.strftime(
+                            "%Y%m" + t.suffix
+                        ).name("formatted")
+                    ]
+                )
+                .formatted
+            ),
+            '%Y%m%d',
+            marks=[
+                pytest.mark.notimpl(["dask", "pandas", "postgres"]),
+                pytest.mark.notyet(["duckdb"]),
+            ],
+            id="column_format_str",
+        ),
+    ],
 )
-@pytest.mark.notimpl(["datafusion", "duckdb", "impala"])
-def test_strftime(backend, con, alltypes, df, ibis_pattern, pandas_pattern):
-    expr = alltypes.timestamp_col.strftime(ibis_pattern)
-    expected = df.timestamp_col.dt.strftime(pandas_pattern)
+@pytest.mark.notimpl(["datafusion", "impala"])
+def test_strftime(backend, alltypes, df, expr_fn, pandas_pattern):
+    expr = expr_fn(alltypes)
+    expected = df.timestamp_col.dt.strftime(pandas_pattern).rename("formatted")
 
     result = expr.execute()
-    expected = backend.default_series_rename(expected)
     backend.assert_series_equal(result, expected)