[fix](fe) Quote variant predefined field comments in generated SQL

fe/fe-core/src/main/java/org/apache/doris/nereids/parser/LogicalPlanBuilder.java

@@ -5537,13 +5537,8 @@ public List<VariantField> visitVariantSubColTypeList(VariantSubColTypeListContex
 
     @Override
     public VariantField visitVariantSubColType(VariantSubColTypeContext ctx) {
-        String comment;
-        if (ctx.commentSpec() != null) {
-            comment = ctx.commentSpec().STRING_LITERAL().getText();
-            comment = LogicalPlanBuilderAssistant.escapeBackSlash(comment.substring(1, comment.length() - 1));
-        } else {
-            comment = "";
-        }
+        String comment = ctx.commentSpec() == null ? ""
+                : SqlLiteralUtils.parseStringLiteral(ctx.commentSpec().STRING_LITERAL().getText());
         String pattern = ctx.STRING_LITERAL().getText();
         pattern = pattern.substring(1, pattern.length() - 1);
         if (ctx.variantSubColMatchType() != null) {

fe/fe-core/src/main/java/org/apache/doris/nereids/types/VariantField.java

@@ -19,6 +19,7 @@
 
 import org.apache.doris.catalog.PatternType;
 import org.apache.doris.common.GlobRegexUtil;
+import org.apache.doris.nereids.util.SqlLiteralUtils;
 import org.apache.doris.nereids.util.Utils;
 
 import com.google.re2j.Pattern;
@@ -118,7 +119,7 @@ public String toSql() {
         sb.append("'").append(pattern).append("'");
         sb.append(":").append(dataType.toSql());
         if (!comment.isEmpty()) {
-            sb.append(" COMMENT '").append(comment).append("'");
+            sb.append(" COMMENT ").append(SqlLiteralUtils.quoteStringLiteral(comment));
         }
         return sb.toString();
     }

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

@@ -17,6 +17,8 @@
 
 package org.apache.doris.catalog;
 
+import org.apache.doris.nereids.parser.NereidsParser;
+
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 
@@ -162,6 +164,21 @@ public void testVariantToSqlSerializesNestedGroupProperty() {
         Assertions.assertTrue(variantType.toSql().contains("\"variant_enable_nested_group\" = \"true\""));
     }
 
+    @Test
+    public void testVariantFieldCommentToSqlRoundTrip() {
+        String comment = "O'Reilly \"quoted\" a\\b";
+        ArrayList<VariantField> fields = new ArrayList<>();
+        fields.add(new VariantField("price", Type.INT, comment));
+        String sql = new VariantType(fields, 0, false, 10000, 1, false, 0L, 64, false).toSql();
+
+        org.apache.doris.nereids.types.VariantType parsed = (org.apache.doris.nereids.types.VariantType)
+                new NereidsParser().parseDataType(sql);
+        Assertions.assertEquals(comment, parsed.getPredefinedFields().get(0).getComment());
+        org.apache.doris.nereids.types.VariantType reparsed = (org.apache.doris.nereids.types.VariantType)
+                new NereidsParser().parseDataType("variant<" + parsed.getPredefinedFields().get(0).toSql() + ">");
+        Assertions.assertEquals(comment, reparsed.getPredefinedFields().get(0).getComment());
+    }
+
     @Test
     public void testVariantToThriftUsesV2() {
         Assertions.assertTrue(new VariantType().toThrift().types.get(0).scalar_type.variant_is_v2);

fe/fe-type/src/main/java/org/apache/doris/catalog/VariantField.java

@@ -17,6 +17,7 @@
 
 package org.apache.doris.catalog;
 
+import org.apache.doris.common.util.SqlUtils;
 import org.apache.doris.thrift.TTypeDesc;
 import org.apache.doris.thrift.TTypeNode;
 
@@ -74,7 +75,8 @@ public String toSql(int depth) {
         sb.append("'").append(pattern).append("'");
         sb.append(":").append(type.toSql(depth + 1));
         if (!comment.isEmpty()) {
-            sb.append(" COMMENT '").append(comment).append("'");
+            // Quote the comment so SHOW CREATE TABLE output can be replayed when it holds quotes or backslashes.
+            sb.append(" COMMENT ").append(SqlUtils.quoteStringLiteral(comment, false));
         }
         return sb.toString();
     }

regression-test/data/variant_p0/predefine/test_variant_predefine_comment_escape.out

@@ -0,0 +1,10 @@
+-- This file is automatically generated. You should know what you did if you want to edit this
+-- !show_create --
+test_variant_predefine_comment_escape	CREATE TABLE `test_variant_predefine_comment_escape` (\n  `id` int NULL,\n  `v` variant<'price':int COMMENT "O'Reilly",'name':text COMMENT "say 'hi' and ""bye""",'path':text COMMENT "C:\\\\tmp",PROPERTIES ("variant_max_subcolumns_count" = "10","variant_enable_typed_paths_to_sparse" = "false","variant_max_sparse_column_statistics_size" = "10000","variant_sparse_hash_shard_count" = "1")> NULL\n) ENGINE=OLAP\nDUPLICATE KEY(`id`)\nDISTRIBUTED BY HASH(`id`) BUCKETS 1\nPROPERTIES (\n"replication_allocation" = "tag.location.default: 1",\n"min_load_replica_num" = "-1",\n"is_being_synced" = "false",\n"storage_medium" = "hdd",\n"storage_format" = "V2",\n"inverted_index_storage_format" = "V3",\n"light_schema_change" = "true",\n"disable_auto_compaction" = "false",\n"group_commit_interval_ms" = "10000",\n"group_commit_data_bytes" = "134217728"\n);
+
+-- !show_create_copy --
+test_variant_predefine_comment_escape_copy	CREATE TABLE `test_variant_predefine_comment_escape_copy` (\n  `id` int NULL,\n  `v` variant<'price':int COMMENT "O'Reilly",'name':text COMMENT "say 'hi' and ""bye""",'path':text COMMENT "C:\\\\tmp",PROPERTIES ("variant_max_subcolumns_count" = "10","variant_enable_typed_paths_to_sparse" = "false","variant_max_sparse_column_statistics_size" = "10000","variant_sparse_hash_shard_count" = "1")> NULL\n) ENGINE=OLAP\nDUPLICATE KEY(`id`)\nDISTRIBUTED BY HASH(`id`) BUCKETS 1\nPROPERTIES (\n"replication_allocation" = "tag.location.default: 1",\n"min_load_replica_num" = "-1",\n"is_being_synced" = "false",\n"storage_medium" = "hdd",\n"storage_format" = "V2",\n"inverted_index_storage_format" = "V3",\n"light_schema_change" = "true",\n"disable_auto_compaction" = "false",\n"group_commit_interval_ms" = "10000",\n"group_commit_data_bytes" = "134217728"\n);
+
+-- !select_copy --
+1	10	n	p
+

regression-test/suites/variant_p0/predefine/test_variant_predefine_comment_escape.groovy

@@ -0,0 +1,44 @@
+// 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.
+
+// SHOW CREATE TABLE must print predefined field comments as SQL literals that can be replayed.
+suite("test_variant_predefine_comment_escape") {
+    sql "DROP TABLE IF EXISTS test_variant_predefine_comment_escape"
+    sql "DROP TABLE IF EXISTS test_variant_predefine_comment_escape_copy"
+    sql """
+        CREATE TABLE test_variant_predefine_comment_escape (
+            id INT,
+            v VARIANT<
+                'price':INT COMMENT "O'Reilly",
+                'name':STRING COMMENT 'say ''hi'' and "bye"',
+                'path':STRING COMMENT 'C:\\\\tmp',
+                PROPERTIES ("variant_max_subcolumns_count" = "10")
+            >
+        ) DUPLICATE KEY(id) DISTRIBUTED BY HASH(id) BUCKETS 1
+        PROPERTIES ("replication_num" = "1")
+    """
+    qt_show_create "SHOW CREATE TABLE test_variant_predefine_comment_escape"
+
+    // Replay the printed DDL under a new name; the copy must print the same comments again.
+    def ddl = sql("SHOW CREATE TABLE test_variant_predefine_comment_escape")[0][1]
+    sql ddl.replace("`test_variant_predefine_comment_escape`", "`test_variant_predefine_comment_escape_copy`")
+    qt_show_create_copy "SHOW CREATE TABLE test_variant_predefine_comment_escape_copy"
+
+    sql """INSERT INTO test_variant_predefine_comment_escape_copy
+            SELECT 1, parse_to_variant('{"price": 10, "name": "n", "path": "p"}')"""
+    order_qt_select_copy "SELECT id, v['price'], v['name'], v['path'] FROM test_variant_predefine_comment_escape_copy"
+}