refactor: fix notnull op with bracket

Author: chelsea-lin

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

@@ -125,7 +125,10 @@ def _(expr: TypedExpr, op: ops.MapOp) -> sge.Expression:
 
 @register_unary_op(ops.notnull_op)
 def _(expr: TypedExpr) -> sge.Expression:
-    return sge.Not(this=sge.Is(this=expr.expr, expression=sge.Null()))
+    return sge.Is(
+        this=sge.paren(expr.expr, copy=False),
+        expression=sg.not_(sge.Null(), copy=False),
+    )
 
 
 @register_ternary_op(ops.where_op)

tests/unit/core/compile/sqlglot/aggregations/snapshots/test_unary_compiler/test_qcut/out.sql

@@ -6,7 +6,9 @@ WITH `bfcte_0` AS (
 ), `bfcte_1` AS (
   SELECT
     *,
-    NOT `int64_col` IS NULL AS `bfcol_4`
+    (
+      `int64_col`
+    ) IS NOT NULL AS `bfcol_4`
   FROM `bfcte_0`
 ), `bfcte_2` AS (
   SELECT
@@ -28,7 +30,9 @@ WITH `bfcte_0` AS (
 ), `bfcte_4` AS (
   SELECT
     *,
-    NOT `int64_col` IS NULL AS `bfcol_10`
+    (
+      `int64_col`
+    ) IS NOT NULL AS `bfcol_10`
   FROM `bfcte_3`
 ), `bfcte_5` AS (
   SELECT

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

@@ -5,7 +5,9 @@ WITH `bfcte_0` AS (
 ), `bfcte_1` AS (
   SELECT
     *,
-    NOT `float64_col` IS NULL AS `bfcol_1`
+    (
+      `float64_col`
+    ) IS NOT NULL AS `bfcol_1`
   FROM `bfcte_0`
 )
 SELECT

tests/unit/core/compile/sqlglot/snapshots/test_compile_window/test_compile_window_w_groupby_rolling/out.sql

@@ -17,7 +17,9 @@ WITH `bfcte_0` AS (
     *
   FROM `bfcte_1`
   WHERE
-    NOT `bfcol_9` IS NULL
+    (
+      `bfcol_9`
+    ) IS NOT NULL
 ), `bfcte_3` AS (
   SELECT
     *,