Relates to Core #184 - Partial Updates

language_specification/projection.md

@@ -14,11 +14,11 @@ the field remains excluded, and vice versa.
 projection := basic_projection | [ basic_projection, ... ]
 basic_projection := field_projection | array_projection
 
-field_projection := { "field": <pattern>, "include": boolean, recursive: boolean }
-array_projection := { "field": <pattern>, "include": boolean,
-                      match: query_expression, project : projection, sort : sort  } }  |
-                    { "field": <pattern>, "include": boolean,
-                      "range": [ from, to ], project : projection, "sort": sort }
+field_projection := { "field": <pattern>, "include": boolean[true], "recursive": boolean[false] }
+array_projection := { "field": <pattern>, "include": boolean[true],
+                      match: query_expression, projection : projection, sort : sort  } }  |
+                    { "field": <pattern>, "include": boolean[true],
+                      "range": [ from, to ], projection : projection, "sort": sort }
 ```
 Examples:
 
@@ -35,13 +35,13 @@ Return everything but firstname:
 Return only those elements of the addresses array with
 city="Raleigh", and only return the streetaddress field.
 ```javascript
- [ { "field": "address", "include": true,
-     "match": { "city": "Raleigh" }, "project": { "streetaddress": true} } ]
+ [ { "field": "addresses", "include": true,
+     "match": { "city": "Raleigh" }, "projection": { "field": "streetaddress"} } ]
 ```
 Return the first 5 addresses
 ```javascript
- [ { "field": "address", "include": true, "range": [ 0, 4 ],
-     "project": { "*", "recursive": true} }]
+ [ { "field": "addresses", "include": true, "range": [ 0, 4 ],
+     "projection": { "*", "recursive": true} }]
 ```
 
 ### Sorting array elements in projection
@@ -63,4 +63,4 @@ projects the array 'someArray', thus the elements are not sorted. Whereas:
  [  { "field": "*", "include": true },
     { "field": "someArray", "include": true, "range": [0,2], "sort": {"someField":"$asc"} } ]
 ```
-Here, both projection expression include "someArray", but the latest inclusion contains the sort, so the array elements are sorted.
+Here, both projection expression include "someArray", but the latest inclusion contains the sort, so the array elements are sorted.

language_specification/update.md

@@ -2,23 +2,32 @@
 ```javascript
 update_expression := partial_update_expression |
                     [ partial_update_expression,...]
+
 partial_update_expression := primitive_update_expression |
                              array_update_expression
+
 primitive_update_expression := { $set : { path : rvalue_expression , ...} } |
+                               { $set : { path : rvalue_expression }, fields : field_projection | [ field_projection, ... ]
                                { $unset : path } |
                                { $unset :[ path, ... ] }
                                { $add : { path : rvalue_expression, ... } }
+
 rvalue_expression := value | { $valueof : path }
+
 value := primitive_value | json_container
+
+field_projection := { "field": <pattern>, "include": boolean[true], "recursive": boolean[false] }
+
 json_container := jsonObjectNode | jsonArrayNode
 
 array_update_expression := { $append : { path : rvalue_expression } } |
                            { $append : { path : [ rvalue_expression, ... ] }} |
                            { $insert : { path : rvalue_expression } } |
                            { $insert : { path : [ rvalue_expression,...] }} |
-                           { $foreach : { path : update_query_expression,
-                                         $update : foreach_update_expression } }
+                           { $foreach : { path : update_query_expression, $update : foreach_update_expression } }
+
 update_query_expression := $all | query_expression
+
 foreach_update_expression := $remove | update_expression
 ```
 
@@ -33,8 +42,10 @@ the first two elements of an array, use:
 ```javascript
      { "$set" : { "path" : value } }
      { "$set" : { "path" : [...] } }
-      { "$set" : { "path" : { ... } } }
-    { "$set" : { "path" : { "$valueof" : field } }
+     { "$set" : { "path" : { ... } } }
+     { "$set" : { "path" : { ... }, "fields" : [...] } }
+     { "$set" : { "path" : { ... }, "fields" : { ... } } }
+     { "$set" : { "path" : { "$valueof" : field } }
      { "$unset" : "path" }  (array index is supported, can be used to
                            remove elements of array)
      { "$add" : { "path" : number } }
@@ -110,6 +121,13 @@ Remove x.y.z from doc.
 ```
 $add is similar to $set
 
+##### Examples of partial updates
+
+```javascript
+{ "$set": { "$this" : { "f1" : "foo", "f2" : "bar" } } , "fields" : { "field" : "f2" } }
+```
+Update an object with the given data, but only update field `f2`.
+
 #### Examples of $foreach
 
 ```javascript
@@ -166,3 +184,20 @@ Set field 'k' in matching elements to 'blah' (".k" means
 ```
 For each element of ```x.y.*.z``` where ```x.y.*.z.arr.p=1``` set ```x.y.*.z.arr.v```
 to the value of ```k``` (k is from root of doc) .
+
+##### Examples of partial updates
+
+```javascript
+"$foreach" : { 
+    "x.y.z" : { 
+        "field" : "f3", " op": "$eq", "value" = "jaber"
+    }, 
+    "$update" : { 
+        "$set": { 
+            "$this" : { "f1" : "foo", "f2" : "bar", "f3" : "jaber" }
+        },
+        "fields" : { "field" : "f2" } 
+    } 
+}
+```
+`x` is an object, `y` is an object, `z` is an array.  Update all objects in array `z` where `z` has a field `f3` that equals `jaber`, but only update field `f2` and set it to `bar`.