AssertEventStreamMaxEventId.cs

using System;
using System.Text;

namespace Marten.Services.Events
{
    public class AssertEventStreamMaxEventId : IStorageOperation
    {
        private readonly Guid stream;
        private readonly int expectedVersion;
        private readonly string tableName;

        public AssertEventStreamMaxEventId(Guid stream, int expectedVersion, string tableName)
        {
            this.stream = stream;
            this.expectedVersion = expectedVersion;
            this.tableName = tableName;
        }

        public string _sql;
        
        void ICall.WriteToSql(StringBuilder builder)
        {
            builder.Append(_sql);
        }

        public void AddParameters(IBatchCommand batch)
        {
            // Parameterized queries won't work here: https://github.com/npgsql/npgsql/issues/331
            _sql = $@"DO $$ BEGIN IF
  (SELECT max(events.version)
   FROM {tableName} AS events
   WHERE events.stream_id = '{stream}') <> {expectedVersion} THEN 
RAISE EXCEPTION 'Unexpected MAX(id) for event stream'; END IF; END; $$;";
        }

        public override string ToString()
        {
            return _sql;
        }
    }
}