[fix](truncate) fix bug that truncate partition throw NPE (#9339)

1. partition name is case insensitive.
2. add a simple help-resource.zip to help pass the FE ut.

.gitignore

@@ -5,7 +5,6 @@
 *.iml
 *.swp
 *.jar
-*.zip
 *.gz
 *.log
 *.so.tmp

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

@@ -6814,7 +6814,7 @@ public class Catalog {
             // check partitions
             for (Map.Entry<String, Long> entry : origPartitions.entrySet()) {
                 Partition partition = copiedTbl.getPartition(entry.getValue());
-                if (partition == null || !partition.getName().equals(entry.getKey())) {
+                if (partition == null || !partition.getName().equalsIgnoreCase(entry.getKey())) {
                     throw new DdlException("Partition [" + entry.getKey() + "] is changed");
                 }
             }

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

@@ -1286,11 +1286,13 @@ public class OlapTable extends Table {
             return copied;
         }
 
-        Set<String> partNames = Sets.newTreeSet(String.CASE_INSENSITIVE_ORDER);
+        Set<String> partNames = Sets.newHashSet();
         partNames.addAll(copied.getPartitionNames());
 
+        // partition name is case insensitive:
+        Set<String> lowerReservedPartitionNames = reservedPartitions.stream().map(String::toLowerCase).collect(Collectors.toSet());
         for (String partName : partNames) {
-            if (!reservedPartitions.contains(partName)) {
+            if (!lowerReservedPartitionNames.contains(partName.toLowerCase())) {
                 copied.dropPartitionAndReserveTablet(partName);
             }
         }

fe/fe-core/src/main/java/org/apache/doris/common/CaseSensibility.java

@@ -22,7 +22,7 @@ public enum CaseSensibility {
     DATABASE(true),
     TABLE(true),
     ROLLUP(true),
-    PARTITION(true),
+    PARTITION(false),
     COLUMN(false),
     USER(true),
     ROLE(false),

fe/fe-core/src/test/java/org/apache/doris/catalog/TruncateTableTest.java

@@ -56,6 +56,24 @@ public class TruncateTableTest {
                                         "properties('replication_num' = '1');";
         createDb(createDbStmtStr);
         createTable(createTableStr);
+
+        String createTable2 = "CREATE TABLE test.case_sensitive_table (\n" +
+                "  `date_id` date NULL COMMENT \"\",\n" +
+                "  `column2` tinyint(4) NULL COMMENT \"\"\n" +
+                ") ENGINE=OLAP\n" +
+                "DUPLICATE KEY(`date_id`, `column2`)\n" +
+                "COMMENT \"OLAP\"\n" +
+                "PARTITION BY RANGE(`date_id`)\n" +
+                "(\n" +
+                "PARTITION p20211006 VALUES [('2021-10-06'), ('2021-10-07')),\n" +
+                "PARTITION P20211007 VALUES [('2021-10-07'), ('2021-10-08')),\n" +
+                "PARTITION P20211008 VALUES [('2021-10-08'), ('2021-10-09')))\n" +
+                "DISTRIBUTED BY HASH(`column2`) BUCKETS 1\n" +
+                "PROPERTIES (\n" +
+                "\"replication_allocation\" = \"tag.location.default: 1\"\n" +
+                ");";
+
+        createTable(createTable2);
     }
 
     @AfterClass
@@ -64,6 +82,29 @@ public class TruncateTableTest {
         file.delete();
     }
 
+    @Test
+    public void testTruncateWithCaseInsensitivePartitionName() throws Exception {
+        Database db = Catalog.getCurrentCatalog().getDbNullable("default_cluster:test");
+        OlapTable tbl = db.getOlapTableOrDdlException("case_sensitive_table");
+        long p20211006Id = tbl.getPartition("P20211006").getId();
+        long p20211007Id = tbl.getPartition("P20211007").getId();
+        long p20211008Id = tbl.getPartition("p20211008").getId();
+        // truncate p20211008(real name is P20211008)
+        String truncateStr = "TRUNCATE TABLE test.case_sensitive_table PARTITION p20211008; \n";
+        TruncateTableStmt truncateTableStmt = (TruncateTableStmt) UtFrameUtils.parseAndAnalyzeStmt(truncateStr, connectContext);
+        Catalog.getCurrentCatalog().truncateTable(truncateTableStmt);
+        Assert.assertNotEquals(p20211008Id, tbl.getPartition("p20211008").getId());
+        // 2. truncate P20211007
+        truncateStr = "TRUNCATE TABLE test.case_sensitive_table PARTITION P20211007; \n";
+        truncateTableStmt = (TruncateTableStmt) UtFrameUtils.parseAndAnalyzeStmt(truncateStr, connectContext);
+        Catalog.getCurrentCatalog().truncateTable(truncateTableStmt);
+        Assert.assertEquals(3, tbl.getPartitionInfo().idToDataProperty.size());
+        Assert.assertNotEquals(p20211007Id, tbl.getPartition("p20211007").getId());
+        Assert.assertEquals(p20211006Id, tbl.getPartition("p20211006").getId());
+        Assert.assertNotNull(tbl.getPartition("p20211006"));
+        Assert.assertNotNull(tbl.getPartition("P20211006"));
+    }
+
     @Test
     public void testTruncateTable() throws Exception {
         String stmtStr = "ALTER TABLE test.tbl ADD PARTITION p20210902 VALUES [('2021-09-02'), ('2021-09-03')) DISTRIBUTED BY HASH(`k1`) BUCKETS 3;";