refactor: support ops.case_when_op for the sqlglot compiler

Author: chelsea-lin

bigframes/core/compile/sqlglot/expressions/generic_ops.py

@@ -23,6 +23,7 @@
 import bigframes.core.compile.sqlglot.scalar_compiler as scalar_compiler
 
 register_unary_op = scalar_compiler.scalar_op_compiler.register_unary_op
+register_nary_op = scalar_compiler.scalar_op_compiler.register_nary_op
 register_ternary_op = scalar_compiler.scalar_op_compiler.register_ternary_op
 
 
@@ -67,18 +68,6 @@ def _(expr: TypedExpr, op: ops.AsTypeOp) -> sge.Expression:
     return _cast(sg_expr, sg_to_type, op.safe)
 
 
-@register_ternary_op(ops.clip_op)
-def _(
-    original: TypedExpr,
-    lower: TypedExpr,
-    upper: TypedExpr,
-) -> sge.Expression:
-    return sge.Greatest(
-        this=sge.Least(this=original.expr, expressions=[upper.expr]),
-        expressions=[lower.expr],
-    )
-
-
 @register_unary_op(ops.hash_op)
 def _(expr: TypedExpr) -> sge.Expression:
     return sge.func("FARM_FINGERPRINT", expr.expr)
@@ -114,6 +103,44 @@ def _(
     return sge.If(this=condition.expr, true=original.expr, false=replacement.expr)
 
 
+@register_ternary_op(ops.clip_op)
+def _(
+    original: TypedExpr,
+    lower: TypedExpr,
+    upper: TypedExpr,
+) -> sge.Expression:
+    return sge.Greatest(
+        this=sge.Least(this=original.expr, expressions=[upper.expr]),
+        expressions=[lower.expr],
+    )
+
+
+@register_nary_op(ops.case_when_op)
+def _(*cases_and_outputs: TypedExpr) -> sge.Expression:
+    # Need to upcast BOOL to INT if any output is numeric
+    result_values = cases_and_outputs[1::2]
+    do_upcast_bool = any(
+        dtypes.is_numeric(t.dtype, include_bool=False) for t in result_values
+    )
+    if do_upcast_bool:
+        result_values = tuple(
+            TypedExpr(
+                sge.Cast(this=val.expr, to="INT64"),
+                dtypes.INT_DTYPE,
+            )
+            if val.dtype == dtypes.BOOL_DTYPE
+            else val
+            for val in result_values
+        )
+
+    return sge.Case(
+        ifs=[
+            sge.If(this=predicate.expr, true=output.expr)
+            for predicate, output in zip(cases_and_outputs[::2], result_values)
+        ],
+    )
+
+
 # Helper functions
 def _cast_to_json(expr: TypedExpr, op: ops.AsTypeOp) -> sge.Expression:
     from_type = expr.dtype

tests/system/small/engines/test_generic_ops.py

@@ -357,7 +357,7 @@ def test_engines_fillna_op(scalars_array_value: array_value.ArrayValue, engine):
     assert_equivalence_execution(arr.node, REFERENCE_ENGINE, engine)
 
 
-@pytest.mark.parametrize("engine", ["polars", "bq"], indirect=True)
+@pytest.mark.parametrize("engine", ["polars", "bq", "bq-sqlglot"], indirect=True)
 def test_engines_casewhen_op_single_case(
     scalars_array_value: array_value.ArrayValue, engine
 ):
@@ -373,7 +373,7 @@ def test_engines_casewhen_op_single_case(
     assert_equivalence_execution(arr.node, REFERENCE_ENGINE, engine)
 
 
-@pytest.mark.parametrize("engine", ["polars", "bq"], indirect=True)
+@pytest.mark.parametrize("engine", ["polars", "bq", "bq-sqlglot"], indirect=True)
 def test_engines_casewhen_op_double_case(
     scalars_array_value: array_value.ArrayValue, engine
 ):

tests/unit/core/compile/sqlglot/expressions/snapshots/test_generic_ops/test_case_when_op/out.sql

@@ -0,0 +1,29 @@
+WITH `bfcte_0` AS (
+  SELECT
+    `bool_col` AS `bfcol_0`,
+    `int64_col` AS `bfcol_1`,
+    `int64_too` AS `bfcol_2`,
+    `float64_col` AS `bfcol_3`
+  FROM `bigframes-dev`.`sqlglot_test`.`scalar_types`
+), `bfcte_1` AS (
+  SELECT
+    *,
+    CASE WHEN `bfcol_0` THEN `bfcol_1` END AS `bfcol_4`,
+    CASE WHEN `bfcol_0` THEN `bfcol_1` WHEN `bfcol_0` THEN `bfcol_2` END AS `bfcol_5`,
+    CASE WHEN `bfcol_0` THEN `bfcol_0` WHEN `bfcol_0` THEN `bfcol_0` END AS `bfcol_6`,
+    CASE
+      WHEN `bfcol_0`
+      THEN `bfcol_1`
+      WHEN `bfcol_0`
+      THEN CAST(`bfcol_0` AS INT64)
+      WHEN `bfcol_0`
+      THEN `bfcol_3`
+    END AS `bfcol_7`
+  FROM `bfcte_0`
+)
+SELECT
+  `bfcol_4` AS `single_case`,
+  `bfcol_5` AS `double_case`,
+  `bfcol_6` AS `bool_types_case`,
+  `bfcol_7` AS `mixed_types_cast`
+FROM `bfcte_1`

tests/unit/core/compile/sqlglot/expressions/test_generic_ops.py

@@ -168,6 +168,47 @@ def test_astype_json_invalid(
         )
 
 
+def test_case_when_op(scalar_types_df: bpd.DataFrame, snapshot):
+    ops_map = {
+        "single_case": ops.case_when_op.as_expr(
+            "bool_col",
+            "int64_col",
+        ),
+        "double_case": ops.case_when_op.as_expr(
+            "bool_col",
+            "int64_col",
+            "bool_col",
+            "int64_too",
+        ),
+        "bool_types_case": ops.case_when_op.as_expr(
+            "bool_col",
+            "bool_col",
+            "bool_col",
+            "bool_col",
+        ),
+        "mixed_types_cast": ops.case_when_op.as_expr(
+            "bool_col",
+            "int64_col",
+            "bool_col",
+            "bool_col",
+            "bool_col",
+            "float64_col",
+        ),
+    }
+
+    array_value = scalar_types_df._block.expr
+    result, col_ids = array_value.compute_values(list(ops_map.values()))
+
+    # Rename columns for deterministic golden SQL results.
+    assert len(col_ids) == len(ops_map.keys())
+    result = result.rename_columns(
+        {col_id: key for col_id, key in zip(col_ids, ops_map.keys())}
+    ).select_columns(list(ops_map.keys()))
+
+    sql = result.session._executor.to_sql(result, enable_cache=False)
+    snapshot.assert_match(sql, "out.sql")
+
+
 def test_clip(scalar_types_df: bpd.DataFrame, snapshot):
     op_expr = ops.clip_op.as_expr("rowindex", "int64_col", "int64_too")