MySQL Bugs: #101252: Can't query CHAR(36) column containing NULL

Bug #101252	Can't query CHAR(36) column containing NULL
Submitted:	20 Oct 2020 20:09	Modified:	27 Jan 2021 18:56
Reporter:	Bradley Grainger (OCA)	Email Updates:
Status:	Closed	Impact on me:	None
Category:	Connector / NET	Severity:	S2 (Serious)
Version:	8.0.22	OS:	Windows (10)
Assigned to:		CPU Architecture:	Any
Tags:	regression

Description:
The column type CHAR(36) is used to represent a GUID in MySQL Server (and MySqlDataReader.GetValue will return a System.Guid value from that column).

Starting in 8.0.22, querying a CHAR(36) column containing NULL values will throw an ArgumentOutOfRangeException.

ArgumentOutOfRangeException: Non-negative number required. (Parameter 'count') 
StackTrace:
   at System.Text.UTF8Encoding.GetString(Byte[] bytes, Int32 index, Int32 count)
   at MySql.Data.MySqlClient.NativeDriver.ReadColumnValue(Int32 index, MySqlField field, IMySqlValue valObject)
   at MySql.Data.MySqlClient.ResultSet.ReadColumnData(Boolean outputParms)
   at MySql.Data.MySqlClient.ResultSet.NextRow(CommandBehavior behavior)
   at MySql.Data.MySqlClient.MySqlDataReader.Read() 

How to repeat:
Run the following C# code:

using var connection = new MySqlConnection("...");
connection.Open();

using var command = new MySqlCommand(@"drop table if exists guid_test;
create table guid_test(value char(36));
insert into guid_test(value) values(null);", connection);
command.ExecuteNonQuery();

command.CommandText = "select value from guid_test;";
using var reader = command.ExecuteReader();
while (reader.Read()) // <-- exception thrown here
{
	Console.WriteLine(reader.IsDBNull(0)); // expected True
}

Suggested fix:
Test for 'length != -1' here: https://github.com/mysql/mysql-connector-net/commit/c8b7779b9f98f6985600483a5331d951f40127...

Hello Bradley,

Thank you for the report and test case.
Verified as described.

regards,
Umesh

Hi,
When will this bug be fixed? I'm getting the same issue when updating to MySql.Data version 8.0.22.

Regards,
Kevin

Posted by developer:
 
Fixed as of the upcoming MySQL Connector/NET 8.0.24 release, and here's the proposed changelog entry from the documentation team:

An exception was thrown if any CHAR(36) columns containing a NULL value
were referenced in a query. New validation now checks for NULL values when
the MySqlDbType member is Guid.

Thank you for the bug report.

Bug #103259 marked as duplicate of this one.

The error persists despite having scaled the versions, from 8.0.24 to 31 to the present.