Fix image columns

[gerhardgruber]

When using MSSQL::Type::Image columns updates to this column always bring an error like "The conversion from UNKNOWN to UNKNOWN is unsupported."

I have a JRuby on Rails application which ran very long with Rails 4.2 (quite well) and now we are upgrading it to 5.2.
Every time when we do an update on a "binary" column (which has the "image" type in the database), we get the error:

[10] pry(main)> Draft.columns_hash[ "data" ]
=> #<ActiveRecord::ConnectionAdapters::MSSQLColumn:0x4ffa078d
 @collation=nil,
 @comment=nil,
 @default=nil,
 @default_function=nil,
 @name="data",
 @null=true,
 @sql_type_metadata=#<ActiveRecord::ConnectionAdapters::SqlTypeMetadata:0x42238078 @limit=2147483647, @precision=nil, @scale=nil, @sql_type="image", @type=:image>,
 @table_name="drafts">
[11] pry(main)> d.data = "test"
=> "test"
[12] pry(main)> d.save!
DEBUG - 2019-10-17 09:44:35 (:83629:2026):    (1.4ms)  BEGIN TRANSACTION
DEBUG - 2019-10-17 09:44:35 (:83629:2026):   Draft Update (2.1ms)  UPDATE [drafts] SET [data] = ?, [updated_at] = ?, [lock_version] = ? WHERE [drafts].[id] = ? AND [drafts].[lock_version] = ?  [["data", "<4 bytes of binary data>"], ["updated_at", 2019-10-17 07:44:35 UTC], ["lock_version", 11], ["id", 192], ["lock_version", 10]]
DEBUG - 2019-10-17 09:44:35 (:83629:2026):    (2.2ms)  ROLLBACK TRANSACTION
ActiveRecord::StatementInvalid: ActiveRecord::JDBCError: com.microsoft.sqlserver.jdbc.SQLServerException: Die Konvertierung von "UNKNOWN" in "UNKNOWN" wird nicht unterstützt.: UPDATE [drafts] SET [data] = ?, [updated_at] = ?, [lock_version] = ? WHERE [drafts].[id] = ? AND [drafts].[lock_version] = ?
from arjdbc/jdbc/RubyJdbcConnection.java:983:in `execute_prepared_update'
Caused by ActiveRecord::JDBCError: com.microsoft.sqlserver.jdbc.SQLServerException: Die Konvertierung von "UNKNOWN" in "UNKNOWN" wird nicht unterstützt.
from arjdbc/jdbc/RubyJdbcConnection.java:983:in `execute_prepared_update'
Caused by Java::ComMicrosoftSqlserverJdbc::SQLServerException: Die Konvertierung von "UNKNOWN" in "UNKNOWN" wird nicht unterstützt.
from com.microsoft.sqlserver.jdbc.SQLServerException.makeFromDriverError(SQLServerException.java:234)

After changing the type map, the code runs:

[2] pry(main)> Draft.columns_hash["data"]
=> #<ActiveRecord::ConnectionAdapters::MSSQLColumn:0x63eea8c4
 @collation=nil,
 @comment=nil,
 @default=nil,
 @default_function=nil,
 @name="data",
 @null=true,
 @sql_type_metadata=#<ActiveRecord::ConnectionAdapters::SqlTypeMetadata:0x19924f15 @limit=2147483647, @precision=nil, @scale=nil, @sql_type="image", @type=:binary>,
 @table_name="drafts">
[3] pry(main)> d.data = "test"
=> "test"
[4] pry(main)> d.save!
DEBUG - 2019-10-17 09:48:17 (:84219:2026):    (2.5ms)  BEGIN TRANSACTION
DEBUG - 2019-10-17 09:48:17 (:84219:2026):   Draft Update (8.2ms)  UPDATE [drafts] SET [updated_at] = ?, [data] = ?, [lock_version] = ? WHERE [drafts].[id] = ? AND [drafts].[lock_version] = ?  [["updated_at", 2019-10-17 07:48:17 UTC], ["data", "<4 bytes of binary data>"], ["lock_version", 11], ["id", 192], ["lock_version", 10]]
DEBUG - 2019-10-17 09:48:17 (:84219:2026):    (10.1ms)  COMMIT TRANSACTION
=> true