Add option to auto-create Properties column as DataType SqlXml

[jducobu]

I work on a console developed in .net core 2.0.
In the appsettings.json file, i have this declaration:

"Serilog": {
    "Using": [ "Serilog.Sinks.MSSqlServer" ],
    "MinimumLevel": "Information",
    "WriteTo": [
      {
        "Name": "MSSqlServer",
        "Args": {
          "connectionString": "Server=.;Database=Serilog;Trusted_Connection=True;MultipleActiveResultSets=true;",
          "tableName": "log",
          "columnOptionsSection": {
            "customColumns": [
              {
                "ColumnName": "EventType",
                "DataType": "int",
                "AllowNull": false
              },
              {
                "ColumnName": "Release",
                "DataType": "varchar",
                "DataLength": 32
              }
            ]
          },
          "autoCreateSqlTable": "true"
        }
      }
    ]
  }

The log table have a properties column's datatype set to nvarchar(max), not xml.

A workaround is to exexute this command :

ALTER TABLE [dbo].[log] ALTER COLUMN Properties XML

[MV10]

I'd strongly disagree with making this a default. Although SQL Server stores the XML data type much more efficiently than the same XML stored as text, it requires extra processing which incurs additional CPU overhead, which potentially reduces write performance -- something you definitely want to avoid when logging. The storage footprint savings are probably irrelevant given that you shouldn't be logging huge data structures. Additionally all of my deployments use JSON for structured data and I'd argue that XML is rapidly falling out of favor.

[MV10]

I'll tag this as an enhancement request since it comes up periodically. Once I grind through the open bugs, I'm going to start looking at new feature requests.

I think it should be implemented as an option with nvarchar remaining the default.

I'd like to start building up a Wiki for this repo since the README is getting unwieldy, and there I'd caution against the XML type in high-frequency logging scenarios.

[MV10]

Currently overhauling configuration and better control over column data types is part of it, including XML column support. Docs will recommend against this for write-performance reasons, most likely.