[fix](fe) Fix PullUpPredicates losing NULL rows in INTERSECT/EXCEPT

fe/fe-core/src/main/java/org/apache/doris/nereids/rules/rewrite/PullUpPredicates.java

@@ -464,11 +464,20 @@ private ImmutableSet<Expression> getFiltersFromUnionConstExprs(LogicalUnion unio
                     break;
                 }
             }
-            options.removeIf(option -> option instanceof NullLiteral);
+            boolean hasNull = options.removeIf(option -> option instanceof NullLiteral);
+            Expression predicate = null;
             if (options.size() > 1) {
-                filtersFromConstExprs.add(new InPredicate(compareExpr, options));
+                predicate = new InPredicate(compareExpr, options);
             } else if (options.size() == 1) {
-                filtersFromConstExprs.add(new EqualTo(compareExpr, options.iterator().next()));
+                predicate = new EqualTo(compareExpr, options.iterator().next());
+            }
+            if (hasNull && predicate != null) {
+                predicate = new Or(predicate, new IsNull(compareExpr));
+            } else if (hasNull) {
+                predicate = new IsNull(compareExpr);
+            }
+            if (predicate != null) {
+                filtersFromConstExprs.add(predicate);
             }
         }
         return ImmutableSet.copyOf(filtersFromConstExprs);

regression-test/data/query_p0/set_operations/test_pullup_predicate_null.out

@@ -0,0 +1,32 @@
+-- This file is automatically generated. You should know what you did if you want to edit this
+-- !intersect_null --
+\N
+2
+
+-- !except_null --
+6
+
+-- !except_null_only_left --
+\N
+
+-- !all_null_intersect --
+\N
+
+-- !union_distinct_null --
+\N
+1
+2
+
+-- !no_null_intersect --
+2
+
+-- !multi_col_null --
+1	\N
+
+-- !table_intersect_null --
+\N
+2
+
+-- !table_except_null --
+1
+

regression-test/suites/query_p0/set_operations/test_pullup_predicate_null.groovy

@@ -0,0 +1,137 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+// Regression test for PullUpPredicates.getFiltersFromUnionConstExprs() incorrectly
+// removing NULL from pulled-up predicates without compensating with OR IS NULL.
+// This caused INTERSECT/EXCEPT to lose NULL rows when InferPredicates pushed down
+// the incomplete IN(...) filter to set operation children.
+suite("test_pullup_predicate_null", "query,p0") {
+    sql "SET enable_nereids_planner=true"
+    sql "SET enable_fallback_to_original_planner=false"
+
+    // Original reproducing case: INTERSECT with NULL in CTE constants
+    // tbl0 n*2 = {2, 6, NULL}, tbl1 n*2 = {4, NULL, 2}
+    // INTERSECT should return {2, NULL}
+    order_qt_intersect_null """
+        WITH
+            tbl0(n) AS (SELECT 1 UNION ALL SELECT 3 UNION ALL SELECT NULL),
+            tbl1(n) AS (SELECT 2 UNION ALL SELECT NULL UNION ALL SELECT 1)
+        (
+            SELECT (n * 2) AS n FROM tbl0
+            INTERSECT
+            SELECT (n * 2) AS n FROM tbl1
+        )
+    """
+
+    // EXCEPT with NULL: {2, 6, NULL} EXCEPT {4, NULL, 2} = {6}
+    order_qt_except_null """
+        WITH
+            tbl0(n) AS (SELECT 1 UNION ALL SELECT 3 UNION ALL SELECT NULL),
+            tbl1(n) AS (SELECT 2 UNION ALL SELECT NULL UNION ALL SELECT 1)
+        (
+            SELECT (n * 2) AS n FROM tbl0
+            EXCEPT
+            SELECT (n * 2) AS n FROM tbl1
+        )
+    """
+
+    // EXCEPT where NULL is only in first set: {1, NULL} EXCEPT {1, 2} = {NULL}
+    order_qt_except_null_only_left """
+        WITH
+            tbl0(n) AS (SELECT 1 UNION ALL SELECT NULL),
+            tbl1(n) AS (SELECT 1 UNION ALL SELECT 2)
+        (
+            SELECT n FROM tbl0
+            EXCEPT
+            SELECT n FROM tbl1
+        )
+    """
+
+    // All-NULL INTERSECT: {NULL} INTERSECT {NULL, 1} = {NULL}
+    order_qt_all_null_intersect """
+        SELECT * FROM (SELECT NULL a UNION ALL SELECT NULL) t1
+        INTERSECT
+        SELECT * FROM (SELECT NULL a UNION ALL SELECT 1) t2
+    """
+
+    // UNION DISTINCT with NULL from both sides
+    order_qt_union_distinct_null """
+        WITH
+            tbl0(n) AS (SELECT 1 UNION ALL SELECT NULL),
+            tbl1(n) AS (SELECT NULL UNION ALL SELECT 2)
+        (
+            SELECT n FROM tbl0
+            UNION
+            SELECT n FROM tbl1
+        )
+    """
+
+    // Non-null case: verify no regression
+    order_qt_no_null_intersect """
+        WITH
+            tbl0(n) AS (SELECT 1 UNION ALL SELECT 3),
+            tbl1(n) AS (SELECT 2 UNION ALL SELECT 1)
+        (
+            SELECT (n * 2) AS n FROM tbl0
+            INTERSECT
+            SELECT (n * 2) AS n FROM tbl1
+        )
+    """
+
+    // Multi-column with NULL in one column
+    order_qt_multi_col_null """
+        WITH
+            t1(a, b) AS (SELECT 1, NULL UNION ALL SELECT 2, 'y'),
+            t2(a, b) AS (SELECT 1, NULL UNION ALL SELECT 3, 'z')
+        (
+            SELECT a, b FROM t1
+            INTERSECT
+            SELECT a, b FROM t2
+        )
+    """
+
+    // Table-based test with NULL values
+    sql "DROP TABLE IF EXISTS test_pullup_null_t1"
+    sql """
+        CREATE TABLE test_pullup_null_t1 (
+            k1 INT NULL
+        ) DISTRIBUTED BY HASH(k1) BUCKETS 3
+        PROPERTIES ("replication_num" = "1")
+    """
+    sql "INSERT INTO test_pullup_null_t1 VALUES (1), (2), (NULL)"
+
+    sql "DROP TABLE IF EXISTS test_pullup_null_t2"
+    sql """
+        CREATE TABLE test_pullup_null_t2 (
+            k1 INT NULL
+        ) DISTRIBUTED BY HASH(k1) BUCKETS 3
+        PROPERTIES ("replication_num" = "1")
+    """
+    sql "INSERT INTO test_pullup_null_t2 VALUES (2), (3), (NULL)"
+
+    order_qt_table_intersect_null """
+        SELECT k1 FROM test_pullup_null_t1
+        INTERSECT
+        SELECT k1 FROM test_pullup_null_t2
+    """
+
+    order_qt_table_except_null """
+        SELECT k1 FROM test_pullup_null_t1
+        EXCEPT
+        SELECT k1 FROM test_pullup_null_t2
+    """
+}