fix(mysql,singlestore)!: support charset (#6633)

* support: charset

* support for mysql as well

* test fixed

* pre-commit

* undo the _sql position

* removed nested from unsupported_args in datatype_sql

* handle nested specific to STRUCT

Author: AbhishekASLK

sqlglot/dialects/mysql.py

@@ -293,6 +293,7 @@ class Parser(parser.Parser):
             TokenType.MOD,
             TokenType.SCHEMA,
             TokenType.VALUES,
+            TokenType.CHARACTER_SET,
         }
 
         CONJUNCTION = {

sqlglot/dialects/singlestore.py

@@ -499,7 +499,6 @@ def _unicode_substitute(m: re.Match[str]) -> str:
             ),
             exp.IsAscii: lambda self, e: f"({self.sql(e, 'this')} RLIKE '^[\x00-\x7f]*$')",
             exp.MD5Digest: lambda self, e: self.func("UNHEX", self.func("MD5", e.this)),
-            exp.Chr: rename_func("CHAR"),
             exp.Contains: rename_func("INSTR"),
             exp.RegexpExtractAll: unsupported_args("position", "occurrence", "group")(
                 lambda self, e: self.func(
@@ -1762,8 +1761,13 @@ def jsonarraycontains_sql(self, expression: exp.JSONArrayContains) -> str:
                 self.func("TO_JSON", expression.this),
             )
 
-        @unsupported_args("kind", "nested", "values")
+        @unsupported_args("kind", "values")
         def datatype_sql(self, expression: exp.DataType) -> str:
+            if expression.args.get("nested") and not expression.is_type(exp.DataType.Type.STRUCT):
+                self.unsupported(
+                    f"Argument 'nested' is not supported for representation of '{expression.this.value}' in SingleStore"
+                )
+
             if expression.is_type(exp.DataType.Type.VARBINARY) and not expression.expressions:
                 # `VARBINARY` must always have a size - if it doesn't, we always generate `BLOB`
                 return "BLOB"

tests/dialects/test_mysql.py

@@ -332,6 +332,7 @@ def test_identity(self):
         )
         self.validate_identity("SELECT SUBSTR(1 FROM 2 FOR 3)", "SELECT SUBSTRING(1, 2, 3)")
         self.validate_identity("SELECT ELT(2, 'foo', 'bar', 'baz') AS Result")
+        self.validate_identity("SELECT CHARSET(CHAR(100 USING utf8))")
 
     def test_types(self):
         for char_type in MySQL.Generator.CHAR_CAST_MAPPING:

tests/dialects/test_singlestore.py

@@ -20,6 +20,7 @@ def test_singlestore(self):
         self.validate_identity("SELECT 1")
         self.validate_identity("SELECT * FROM `users` ORDER BY ALL")
         self.validate_identity("SELECT ELT(2, 'foo', 'bar', 'baz')")
+        self.validate_identity("SELECT CHARSET(CHAR(100 USING utf8))")
         self.validate_identity("SELECT TO_JSON(ROW(1, 2) :> RECORD(a INT, b INT))")
 
     def test_byte_strings(self):