implement expression updaters

Author: eiriktsarpalis

src/FSharp.DynamoDB/Expression/ConditionalExpr.fs

@@ -279,14 +279,14 @@ let extractQueryExpr (recordInfo : RecordInfo) (expr : Expr) : ConditionalExpres
                 if not <| isValidFieldName key then
                     invalidArg key "map key must be alphanumeric not starting with a digit"
 
-                Attribute_Exists (attr.Id.Append key)
+                Attribute_Exists (attr.Id.AppendField key)
 
             | SpecificCall2 <@ fun (x : Map<_,_>) y -> x.ContainsKey y @> (Some(AttributeGet attr), _, _, [key]) when key.IsClosed ->
                 let key = evalRaw key
                 if not <| isValidFieldName key then
                     invalidArg key "map key must be alphanumeric not starting with a digit"
 
-                Attribute_Exists (attr.Id.Append key)
+                Attribute_Exists (attr.Id.AppendField key)
 
             | SpecificCall2 <@ BETWEEN @> (None, _, _, [value ; lower; upper]) ->
                 let pickler = Pickler.resolveUntyped value.Type

src/FSharp.DynamoDB/Expression/ExprCommon.fs

@@ -21,20 +21,24 @@ open Swensen.Unquote
 /// DynamoDB Attribute identifier
 type AttributeId = 
     { 
-        Path : string
         RootName : string
         RootId : string
+        NestedPath : string list
         Type : AttributeType 
     }
 with
+    member id.Id = String.concat "" (id.RootId :: id.NestedPath)
+    member id.Name = String.concat "" (id.RootName :: id.NestedPath)
+    member id.Tokens = id.RootName :: id.NestedPath
     member id.IsHashKey = id.Type = AttributeType.HashKey
     member id.IsRangeKey = id.Type = AttributeType.RangeKey
-    member id.Append(suffix) = { id with Path = sprintf "%s.%s" id.Path suffix }
+    member id.AppendField(suffix) = { id with NestedPath = id.NestedPath @ ["." + suffix] }
+    member id.AppendIndex(index) = { id with NestedPath = id.NestedPath @ [sprintf "[%d]" index] }
 
     static member FromKeySchema(schema : TableKeySchema) =
         let rootId = "#HKEY"
         let hkName = schema.HashKey.AttributeName
-        { Path = rootId ; RootId = rootId ; RootName = hkName ; Type = AttributeType.HashKey }
+        { RootId = rootId ; RootName = hkName ; NestedPath = [] ; Type = AttributeType.HashKey }
 
 type RecordPropertyInfo with
     /// Gets an attribute Id for given record property that
@@ -67,17 +71,6 @@ with
 
         aux ap
 
-    /// Gets a list of string tokens that identify the attribute path
-    member ap.Tokens =
-        let rec getTokens acc ap =
-            match ap with
-            | Root rp -> rp.Name :: acc
-            | Nested (rp,p) -> getTokens ("." + rp.Name :: acc) p
-            | Item(i,_,p) -> getTokens (sprintf ".[%d]" i :: acc) p
-            | Optional(_,p) -> getTokens acc p
-
-        getTokens [] ap
-
     /// Gets an attribute identifier for given Quoted attribute instace
     member ap.Id =
         let rec getTokens acc ap =
@@ -87,9 +80,9 @@ with
             | Optional(_,p) -> getTokens acc p
             | Root rp ->
                 {
-                    Path = String.concat "" (rp.AttrId :: acc)
                     RootId = rp.AttrId
                     RootName = rp.Name
+                    NestedPath = acc
                     Type = rp.AttributeType
                 }
 
@@ -192,7 +185,7 @@ type AttributeWriter(names : Dictionary<string, string>, values : Dictionary<str
 
     member __.WriteAttibute(attr : AttributeId) =
         names.[attr.RootId] <- attr.RootName
-        attr.Path
+        attr.Id
 
 /// Recognizes exprs of shape <@ fun p1 p2 ... -> body @>
 let extractExprParams (recordInfo : RecordInfo) (expr : Expr) =
@@ -220,9 +213,9 @@ let extractExprParams (recordInfo : RecordInfo) (expr : Expr) =
 // however 'r.Foo.Bar.[0]' and 'r.Foo.Bar.[1]' are not conflicting
 type private AttributeNode = { Value : string ; Children : ResizeArray<AttributeNode> }
 /// Detects conflicts in a collection of attribute paths
-let tryFindConflictingPaths (attrs : seq<QuotedAttribute>) =
+let tryFindConflictingPaths (attrs : seq<AttributeId>) =
     let root = new ResizeArray<AttributeNode>()
-    let tryAppendPath (attr : QuotedAttribute) =
+    let tryAppendPath (attr : AttributeId) =
         let tokens = attr.Tokens :> seq<string>
         let enum = tokens.GetEnumerator()
         let mutable ctx = root

src/FSharp.DynamoDB/Expression/ExpressionContainers.fs

@@ -94,4 +94,22 @@ type UpdateExpression<'TRecord> internal (updateOps : UpdateOperations) =
         | :? UpdateExpression<'TRecord> as other -> updateOps.UpdateOps = other.UpdateOps.UpdateOps
         | _ -> false
 
-    override __.GetHashCode() = hash updateOps.UpdateOps
+    override __.GetHashCode() = hash updateOps.UpdateOps
+
+
+type UpdateExpression =
+    /// Combines a collection of compatible update expressions into a single expression.
+    static member Combine([<ParamArray>]exprs : UpdateExpression<'TRecord> []) =
+        match exprs with
+        | [||] -> invalidArg "exprs" "must specify at least one update expression."
+        | [|expr|] -> expr
+        | _ ->
+
+        let uops = exprs |> Array.collect (fun e -> e.UpdateOps.UpdateOps)
+        match uops |> Seq.map (fun o -> o.Attribute) |> tryFindConflictingPaths with
+        | None -> ()
+        | Some(p1,p2) ->
+            let msg = sprintf "found conflicting paths '%s' and '%s' being accessed in update expression." p1 p2
+            invalidArg "expr" msg
+
+        new UpdateExpression<'TRecord>({ UpdateOps = uops ; NParams = 0 })

src/FSharp.DynamoDB/Expression/UpdateExpr.fs

@@ -187,7 +187,7 @@ let extractOpExprUpdaters (recordInfo : RecordInfo) (expr : Expr) : Intermediate
 
         do extract body
 
-        match tryFindConflictingPaths attrs with
+        match attrs |> Seq.map (fun attr -> attr.Id) |> tryFindConflictingPaths with
         | Some (p1,p2) -> 
             let msg = sprintf "found conflicting paths '%s' and '%s' being accessed in update expression." p1 p2
             invalidArg "expr" msg
@@ -308,15 +308,15 @@ let extractUpdateOps (exprs : IntermediateUpdateExprs) =
 
         | SpecificCall2 <@ Map.add @> (None, _, _, [keyE; value; AttributeGet attr]) when attr = parent ->
             let key = evalRaw keyE
-            let attr = parent.Id.Append key
+            let attr = parent.Id.AppendField key
             let ep = getElemPickler parent.Pickler
             match extractUpdateValue ep value with
             | Operand op when op = Undefined -> Remove attr
             | uv -> Set(attr, uv)
 
         | SpecificCall2 <@ Map.remove @> (None, _, _, [keyE; AttributeGet attr]) when attr = parent ->
             let key = evalRaw keyE
-            let attr = parent.Id.Append key
+            let attr = parent.Id.AppendField key
             Remove attr
 
         | e -> 
@@ -333,7 +333,7 @@ let extractUpdateOps (exprs : IntermediateUpdateExprs) =
             if uop.Attribute.IsHashKey then invalidArg "expr" "update expression cannot update hash key."
             if uop.Attribute.IsRangeKey then invalidArg "expr" "update expression cannot update range key."
             uop)
-        |> Seq.sortBy (fun uop -> uop.Id, uop.Attribute.Path)
+        |> Seq.sortBy (fun uop -> uop.Id, uop.Attribute.Id)
         |> Seq.toArray
 
     if updateOps.Length = 0 then invalidArg "expr" "No update clauses found in expression"
@@ -397,7 +397,7 @@ let applyParams (uops : UpdateOperations) (inputValues : obj[]) =
         uops.UpdateOps
         |> Seq.map applyUpdateOp
         |> Seq.filter (function Skip -> false | _ -> true)
-        |> Seq.sortBy (fun uop -> uop.Id, uop.Attribute.Path)
+        |> Seq.sortBy (fun uop -> uop.Id, uop.Attribute.Id)
         |> Seq.toArray
 
     { UpdateOps = updateOps' ; NParams = 0 }