From cf253dc9e0d6ab1591393dc67b5a8e79023d9e48 Mon Sep 17 00:00:00 2001
From: George Sittas <giwrgos.sittas@gmail.com>
Date: Mon, 9 Sep 2024 17:49:15 +0300
Subject: [PATCH] Fix(mysql): convert VARCHAR without size to TEXT for DDLs

---
 sqlglot/dialects/doris.py     |  1 +
 sqlglot/dialects/mysql.py     | 10 ++++++++++
 sqlglot/dialects/starrocks.py |  1 +
 tests/dialects/test_mysql.py  |  8 ++++++++
 4 files changed, 20 insertions(+)

diff --git a/sqlglot/dialects/doris.py b/sqlglot/dialects/doris.py
index 0891b495fa..05fb32ade8 100644
--- a/sqlglot/dialects/doris.py
+++ b/sqlglot/dialects/doris.py
@@ -40,6 +40,7 @@ class Parser(MySQL.Parser):
 
     class Generator(MySQL.Generator):
         LAST_DAY_SUPPORTS_DATE_PART = False
+        VARCHAR_REQUIRES_SIZE = False
 
         TYPE_MAPPING = {
             **MySQL.Generator.TYPE_MAPPING,
diff --git a/sqlglot/dialects/mysql.py b/sqlglot/dialects/mysql.py
index 2508596283..ff9042042b 100644
--- a/sqlglot/dialects/mysql.py
+++ b/sqlglot/dialects/mysql.py
@@ -690,6 +690,7 @@ class Generator(generator.Generator):
         PARSE_JSON_NAME: t.Optional[str] = None
         PAD_FILL_PATTERN_IS_REQUIRED = True
         WRAP_DERIVED_VALUES = False
+        VARCHAR_REQUIRES_SIZE = True
 
         TRANSFORMS = {
             **generator.Generator.TRANSFORMS,
@@ -1117,10 +1118,19 @@ def extract_sql(self, expression: exp.Extract) -> str:
             return super().extract_sql(expression)
 
         def datatype_sql(self, expression: exp.DataType) -> str:
+            if (
+                self.VARCHAR_REQUIRES_SIZE
+                and expression.is_type(exp.DataType.Type.VARCHAR)
+                and not expression.expressions
+            ):
+                # `VARCHAR` must always have a size - if it doesn't, we always generate `TEXT`
+                return "TEXT"
+
             # https://dev.mysql.com/doc/refman/8.0/en/numeric-type-syntax.html
             result = super().datatype_sql(expression)
             if expression.this in self.UNSIGNED_TYPE_MAPPING:
                 result = f"{result} UNSIGNED"
+
             return result
 
         def jsonarraycontains_sql(self, expression: exp.JSONArrayContains) -> str:
diff --git a/sqlglot/dialects/starrocks.py b/sqlglot/dialects/starrocks.py
index f38c4e6d4a..d447f59797 100644
--- a/sqlglot/dialects/starrocks.py
+++ b/sqlglot/dialects/starrocks.py
@@ -73,6 +73,7 @@ def _parse_unnest(self, with_alias: bool = True) -> t.Optional[exp.Unnest]:
     class Generator(MySQL.Generator):
         EXCEPT_INTERSECT_SUPPORT_ALL_CLAUSE = False
         JSON_TYPE_REQUIRED_FOR_EXTRACTION = False
+        VARCHAR_REQUIRES_SIZE = False
         PARSE_JSON_NAME: t.Optional[str] = "PARSE_JSON"
         WITH_PROPERTIES_PREFIX = "PROPERTIES"
 
diff --git a/tests/dialects/test_mysql.py b/tests/dialects/test_mysql.py
index 2fd9ef07dc..2f1f7ba57b 100644
--- a/tests/dialects/test_mysql.py
+++ b/tests/dialects/test_mysql.py
@@ -81,6 +81,10 @@ def test_ddl(self):
         self.validate_identity(
             "CREATE OR REPLACE VIEW my_view AS SELECT column1 AS `boo`, column2 AS `foo` FROM my_table WHERE column3 = 'some_value' UNION SELECT q.* FROM fruits_table, JSON_TABLE(Fruits, '$[*]' COLUMNS(id VARCHAR(255) PATH '$.$id', value VARCHAR(255) PATH '$.value')) AS q",
         )
+        self.validate_identity(
+            "CREATE TABLE t (name VARCHAR)",
+            "CREATE TABLE t (name TEXT)",
+        )
         self.validate_identity(
             "ALTER TABLE t ADD KEY `i` (`c`)",
             "ALTER TABLE t ADD INDEX `i` (`c`)",
@@ -175,6 +179,10 @@ def test_identity(self):
         self.validate_identity(
             "REPLACE INTO table SELECT id FROM table2 WHERE cnt > 100", check_command_warning=True
         )
+        self.validate_identity(
+            "CAST(x AS VARCHAR)",
+            "CAST(x AS CHAR)",
+        )
         self.validate_identity(
             """SELECT * FROM foo WHERE 3 MEMBER OF(info->'$.value')""",
             """SELECT * FROM foo WHERE 3 MEMBER OF(JSON_EXTRACT(info, '$.value'))""",