[branch-2.1](auto-partition) fix auto partition expr change unexpected (#36345)

fe/fe-core/src/main/java/org/apache/doris/catalog/PartitionInfo.java

@@ -249,8 +249,9 @@ public boolean enableAutomaticPartition() {
         return isAutoCreatePartitions;
     }
 
+    // forbid change metadata.
     public ArrayList<Expr> getPartitionExprs() {
-        return this.partitionExprs;
+        return Expr.cloneList(this.partitionExprs);
     }
 
     public void checkPartitionItemListsMatch(List<PartitionItem> list1, List<PartitionItem> list2) throws DdlException {

fe/fe-core/src/test/java/org/apache/doris/analysis/PartitionPruneTestBase.java

@@ -34,7 +34,9 @@ protected void doTest() throws Exception {
     }
 
     private void assertExplainContains(String sql, String subString) throws Exception {
-        Assert.assertTrue(String.format("sql=%s, expectResult=%s", sql, subString),
+        Assert.assertTrue(
+                String.format("sql=%s, expectResult=%s, but got %s", sql, subString,
+                        getSQLPlanOrErrorMsg("explain " + sql)),
                 getSQLPlanOrErrorMsg("explain " + sql).contains(subString));
     }
 

fe/fe-core/src/test/java/org/apache/doris/analysis/RangePartitionPruneTest.java

@@ -206,9 +206,6 @@ private void initTestCases() {
                 "partitions=6/8");
         addCase("select /*+ SET_VAR(enable_nereids_planner=false) */ * from test.test_to_date_trunc where event_day= \"2023-08-07 11:00:00\" ",
                 "partitions=1/2");
-        addCase("select /*+ SET_VAR(enable_nereids_planner=false) */ * from test.test_to_date_trunc where date_trunc(event_day, \"day\")= \"2023-08-07 11:00:00\" ",
-                "partitions=1/2");
-
     }
 
 

regression-test/suites/nereids_rules_p0/partition_prune/test_date_function_prune.groovy

@@ -91,4 +91,35 @@ suite("test_date_function_prune") {
         sql "select * from dp where date_time > str_to_date('2020-01-02','%Y-%m-%d')"
         contains("partitions=2/3 (p2,p3)")
     }
+
+    sql "drop table if exists test_to_date_trunc"
+    sql """
+        CREATE TABLE test_to_date_trunc(
+            event_day DATETIME NOT NULL
+        )
+        DUPLICATE KEY(event_day)
+        AUTO PARTITION BY range (date_trunc(event_day, "day")) (
+            PARTITION `p20230807` values [(20230807 ), (20230808 )),
+            PARTITION `p20020106` values [(20020106 ), (20020107 ))
+        )
+        DISTRIBUTED BY HASH(event_day) BUCKETS 4
+        PROPERTIES("replication_num" = "1");
+    """
+    explain {
+        sql """ select /*+ SET_VAR(enable_nereids_planner=false) */ * from test_to_date_trunc where date_trunc(event_day, "day")= "2023-08-07 11:00:00" """
+        contains("partitions=0/2")
+    }
+    explain {
+        sql """ select * from test_to_date_trunc where date_trunc(event_day, "day")= "2023-08-07 11:00:00" """
+        contains("VEMPTYSET")
+    }
+    sql """ insert into test_to_date_trunc values ("20230807000000"); """
+    explain {
+        sql """ select /*+ SET_VAR(enable_nereids_planner=false) */ * from test_to_date_trunc where date_trunc(event_day, "day")= "2023-08-07 11:00:00" """
+        contains("partitions=1/2 (p20230807)")
+    }
+    explain {
+        sql """ select * from test_to_date_trunc where date_trunc(event_day, "day")= "2023-08-07 11:00:00" """
+        contains("partitions=1/2 (p20230807)")
+    }
 }