[fix](schema-change) Complete check for string type length change

fe/fe-core/src/main/java/org/apache/doris/alter/SchemaChangeHandler.java

@@ -630,7 +630,7 @@ private boolean processModifyColumn(ModifyColumnClause alterClause, OlapTable ol
                     // TODO:the case where columnPos is not empty has not been considered
                     if (columnPos == null && col.getDataType() == PrimitiveType.VARCHAR
                             && modColumn.getDataType() == PrimitiveType.VARCHAR) {
-                        ColumnType.checkSupportSchemaChangeForCharType(col.getType(), modColumn.getType());
+                        ColumnType.checkForTypeLengthChange(col.getType(), modColumn.getType());
                         lightSchemaChange = olapTable.getEnableLightSchemaChange();
                     }
                     if (columnPos == null && col.getDataType().isComplexType()

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

@@ -883,6 +883,10 @@ public void checkSchemaChangeAllowed(Column other) throws DdlException {
             }
         }
 
+        if (type.isStringType() && other.type.isStringType()) {
+            ColumnType.checkForTypeLengthChange(type, other.type);
+        }
+
         // Nested types only support changing the order and increasing the length of the nested char type
         // Char-type only support length growing
         ColumnType.checkSupportSchemaChangeForComplexType(type, other.type, false);

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

@@ -169,19 +169,31 @@ static boolean isSchemaChangeAllowed(Type lhs, Type rhs) {
         return schemaChangeMatrix[lhs.getPrimitiveType().ordinal()][rhs.getPrimitiveType().ordinal()];
     }
 
+    /**
+     * Used for checking type length changing.
+     * Currently, type length is only meaningful for string types{@link Type#isStringType()},
+     * see {@link ScalarType#len}.
+     */
+    public static void checkForTypeLengthChange(Type src, Type dst) throws DdlException {
+        final int srcTypeLen = src.getLength();
+        final int dstTypeLen = dst.getLength();
+        if (srcTypeLen < 0 || dstTypeLen < 0) {
+            // type length is negative means that it is meaningless, just return
+            return;
+        }
+        if (srcTypeLen > dstTypeLen) {
+            throw new DdlException(
+                String.format("Shorten type length is prohibited, srcType=%s, dstType=%s", src.toSql(), dst.toSql()));
+        }
+    }
+
     // This method defines the char type
     // to support the schema-change behavior of length growth.
     // return true if the checkType and other are both char-type otherwise return false,
     // which used in checkSupportSchemaChangeForComplexType
-    public static boolean checkSupportSchemaChangeForCharType(Type checkType, Type other) throws DdlException {
-        if ((checkType.getPrimitiveType() == PrimitiveType.VARCHAR && other.getPrimitiveType() == PrimitiveType.VARCHAR)
-                || (checkType.getPrimitiveType() == PrimitiveType.CHAR
-                && other.getPrimitiveType() == PrimitiveType.VARCHAR)
-                || (checkType.getPrimitiveType() == PrimitiveType.CHAR
-                && other.getPrimitiveType() == PrimitiveType.CHAR)) {
-            if (checkType.getLength() > other.getLength()) {
-                throw new DdlException("Cannot shorten string length");
-            }
+    private static boolean checkSupportSchemaChangeForCharType(Type checkType, Type other) throws DdlException {
+        if (checkType.isStringType() && other.isStringType()) {
+            checkForTypeLengthChange(checkType, other);
             return true;
         } else {
             // types equal can return true

regression-test/data/schema_change_p0/test_type_length_change.out

@@ -0,0 +1,21 @@
+-- This file is automatically generated. You should know what you did if you want to edit this
+-- !master_sql --
+1	abc	abc
+2	abcde	abc
+
+-- !master_sql --
+1	abc	abc
+2	abcde	abc
+3	abcde	abcde
+
+-- !master_sql --
+1	abc	abc
+2	abcde	abc
+3	abcde	abcde
+4	abcde	abcde
+
+-- !master_sql --
+k	int	Yes	true	\N	
+c0	varchar(6)	Yes	true	\N	
+c1	varchar(6)	Yes	true	\N	
+

regression-test/suites/schema_change_p0/test_type_length_change.groovy

@@ -0,0 +1,77 @@
+// 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.
+
+suite("test_type_length_change", "p0") {
+    def tableName = "test_type_length_change";
+    sql """ DROP TABLE IF EXISTS ${tableName} """
+    sql """
+        CREATE TABLE ${tableName}
+        (
+            k INT,
+            c0 CHAR(5),
+            c1 VARCHAR(5)
+        )
+        PROPERTIES ( "replication_allocation" = "tag.location.default: 1");
+    """
+
+    def getTableStatusSql = " SHOW ALTER TABLE COLUMN WHERE IndexName='${tableName}' ORDER BY createtime DESC LIMIT 1  "
+
+    sql """ INSERT INTO ${tableName} VALUES(1, "abc", "abc") """
+
+    test {
+        sql """ ALTER TABLE ${tableName} MODIFY COLUMN c0 CHAR(3) """
+        exception "Shorten type length is prohibited"
+    }
+
+    sql """ ALTER TABLE ${tableName} MODIFY COLUMN c0 CHAR(6) """
+    waitForSchemaChangeDone {
+        sql getTableStatusSql
+        time 600
+    }
+
+    sql """  INSERT INTO ${tableName} VALUES(2, "abcde", "abc") """
+    qt_master_sql """ SELECT * FROM ${tableName} ORDER BY k"""
+
+    test {
+        sql """ ALTER TABLE ${tableName} MODIFY COLUMN c1 VARCHAR(3) """
+        exception "Shorten type length is prohibited"
+    }
+
+    sql """ ALTER TABLE ${tableName} MODIFY COLUMN c1 VARCHAR(6) """
+    waitForSchemaChangeDone {
+        sql getTableStatusSql
+        time 600
+    }
+
+    sql """  INSERT INTO ${tableName} VALUES(3, "abcde", "abcde") """
+    qt_master_sql """ SELECT * FROM ${tableName} ORDER BY k"""
+
+    test {
+        sql """ ALTER TABLE ${tableName} MODIFY COLUMN c0 VARCHAR(3) """
+        exception "Shorten type length is prohibited"
+    }
+
+    sql """ ALTER TABLE ${tableName} MODIFY COLUMN c0 VARCHAR(6) """
+    waitForSchemaChangeDone {
+        sql getTableStatusSql
+        time 600
+    }
+
+    sql """  INSERT INTO ${tableName} VALUES(4, "abcde", "abcde") """
+    qt_master_sql """ SELECT * FROM ${tableName} ORDER BY k"""
+    qt_master_sql """ DESC ${tableName} """
+}

regression-test/suites/schema_change_p0/test_varchar_sc_in_complex.groovy

@@ -62,19 +62,19 @@ suite ("test_varchar_sc_in_complex") {
         test {
             sql """ alter table ${tableName} modify column c_a array<varchar(3)>
                 """
-            exception "Cannot shorten string length"
+            exception "Shorten type length is prohibited"
         }
 
         test {
             sql """ alter table ${tableName} modify column c_m map<varchar(3),varchar(3)>
                 """
-            exception "Cannot shorten string length"
+            exception "Shorten type length is prohibited"
         }
 
         test {
             sql """ alter table ${tableName} modify column c_s struct<col:varchar(3)>
                 """
-            exception "Cannot shorten string length"
+            exception "Shorten type length is prohibited"
         }
 
         // add case alter modify array/map/struct to other type

regression-test/suites/schema_change_p0/test_varchar_schema_change.groovy

@@ -55,7 +55,7 @@ suite ("test_varchar_schema_change") {
         test {
             sql """ alter table ${tableName} modify column c2 varchar(10)
                 """
-            exception "Cannot shorten string length"
+            exception "Shorten type length is prohibited"
         }
 
         // test {//为什么第一次改没发生Nothing is changed错误？查看branch-1.2-lts代码