anchor.diff:                      None
                   
               mayBeUsableSource
  +            |> Option.map (
  +                fun x -> x, sqlSources
  +            )
               |> Option.defaultWith (fun () ->
  -                {
  -                    Schema = schema
  -                    Columns =
  -                        schema.Columns
  -                        |> Seq.toList
  -                        |> List.map (fun col -> { Schema = schema.GetColumn(col) })
  -                }
  +                let newSource =
  +                    {
  +                        Schema = schema
  +                        Columns =
  +                            schema.Columns
  +                            |> Seq.toList
  +                            |> List.map (fun col -> { Schema = schema.GetColumn(col) })
  +                    }
  +                let updatedSources = newSource :: (sqlSources |> Map.tryFind pattern |> Option.defaultValue List.empty)
  +                newSource, sqlSources |> Map.add pattern updatedSources
               )
   
           | Statement _ -> "SQL Statements are not yet supported" |> NotImplementedException |> raise
  -        |> fun x ->
  -            let updatedSources = sqlSources |> Map.tryFind pattern |> Option.defaultValue List.empty |> fun xs -> x :: xs
  -            x, sqlSources |> Map.add pattern updatedSources
   
       let applyPatternMatch filters (valueBindings: Map<_,_>) source pattern mapping =
           let variables =
  
positive.code:             }
  
  let private expressionSetValuesEqualCondition left right =
      sprintf "ExpressionSet equality for %A and %A" left right |> NotImplementedException |> raise
  
  let private valueBinderValueEqualToNodeCondition typeIndexer valueBinder node =
      (valueBinder |> valueBinderToExpressionSet typeIndexer, node |> nodeToExpressionSet typeIndexer)
  
negative.code:             neededVariables
              |> List.map (
                  fun var ->
                      var, source |> SqlSource.getColumn var |> Column
              )
              |> Map.ofList
  
  