Merge pull request louischatriot#364 from mitsos1os/$elemMatch

Implement $elemMatch operator

.gitignore

@@ -6,7 +6,7 @@ lib-cov
 *.out
 *.pid
 *.gz
-
+.idea
 pids
 logs
 results

README.md

@@ -271,7 +271,7 @@ db.find({ planet: { $regex: /ar/, $nin: ['Jupiter', 'Earth'] } }, function (err,
 ```
 
 #### Array fields
-When a field in a document is an array, NeDB first tries to see if the query value is an array to perform an exact match, then whether there is an array-specific comparison function (for now there is only `$size`) being used. If not, the query is treated as a query on every element and there is a match if at least one element matches.
+When a field in a document is an array, NeDB first tries to see if the query value is an array to perform an exact match, then whether there is an array-specific comparison function (for now there is only `$size` and `$elemMatch`) being used. If not, the query is treated as a query on every element and there is a match if at least one element matches.
 
 ```javascript
 // Exact match
@@ -283,6 +283,20 @@ db.find({ satellites: ['Deimos', 'Phobos'] }, function (err, docs) {
 })
 
 // Using an array-specific comparison function
+// $elemMatch operator will provide match for a document, if an element from the array field satisfies all the conditions specified with the `$elemMatch` operator
+db.find({ completeData: { planets: { $elemMatch: { name: 'Earth', number: 3 } } } }, function (err, docs) {
+  // docs contains documents with id 5 (completeData)
+});
+
+db.find({ completeData: { planets: { $elemMatch: { name: 'Earth', number: 5 } } } }, function (err, docs) {
+  // docs is empty
+});
+
+// You can use inside #elemMatch query any known document query operator
+db.find({ completeData: { planets: { $elemMatch: { name: 'Earth', number: { $gt: 2 } } } } }, function (err, docs) {
+  // docs contains documents with id 5 (completeData)
+});
+
 // Note: you can't use nested comparison functions, e.g. { $size: { $lt: 5 } } will throw an error
 db.find({ satellites: { $size: 2 } }, function (err, docs) {
   // docs contains Mars

lib/model.js

@@ -622,7 +622,20 @@ comparisonFunctions.$size = function (obj, value) {
 
     return (obj.length == value);
 };
+comparisonFunctions.$elemMatch = function (obj, value) {
+  if (!util.isArray(obj)) { return false; }
+  var i = obj.length;
+  var result = false;   // Initialize result
+  while (i--) {
+    if (match(obj[i], value)) {   // If match for array element, return true
+      result = true;
+      break;
+    }
+  }
+  return result;
+};
 arrayComparisonFunctions.$size = true;
+arrayComparisonFunctions.$elemMatch = true;
 
 
 /**

test/model.test.js

@@ -1216,6 +1216,30 @@ describe('Model', function () {
         model.match({ childrens: [ 'Riri', 'Fifi', 'Loulou' ] }, { "childrens": { $size: 3, $size: 4 } }).should.equal(false);   // Of course this can never be true
       });
 
+      it('Can query array documents with multiple simultaneous conditions', function () {
+        // Non nested documents
+        model.match({ childrens: [ { name: "Huey", age: 3 }, { name: "Dewey", age: 7 }, { name: "Louie", age: 12 } ] }, { "childrens": { $elemMatch: { name: "Dewey", age: 7 } } }).should.equal(true);
+        model.match({ childrens: [ { name: "Huey", age: 3 }, { name: "Dewey", age: 7 }, { name: "Louie", age: 12 } ] }, { "childrens": { $elemMatch: { name: "Dewey", age: 12 } } }).should.equal(false);
+        model.match({ childrens: [ { name: "Huey", age: 3 }, { name: "Dewey", age: 7 }, { name: "Louie", age: 12 } ] }, { "childrens": { $elemMatch: { name: "Louie", age: 3 } } }).should.equal(false);
+
+        // Nested documents
+        model.match({ outer: { childrens: [ { name: "Huey", age: 3 }, { name: "Dewey", age: 7 }, { name: "Louie", age: 12 } ] } }, { "outer.childrens": { $elemMatch: { name: "Dewey", age: 7 } } }).should.equal(true);
+        model.match({ outer: { childrens: [ { name: "Huey", age: 3 }, { name: "Dewey", age: 7 }, { name: "Louie", age: 12 } ] } }, { "outer.childrens": { $elemMatch: { name: "Dewey", age: 12 } } }).should.equal(false);
+        model.match({ outer: { childrens: [ { name: "Huey", age: 3 }, { name: "Dewey", age: 7 }, { name: "Louie", age: 12 } ] } }, { "outer.childrens": { $elemMatch: { name: "Louie", age: 3 } } }).should.equal(false);
+
+      });
+
+      it('$elemMatch operator works with empty arrays', function () {
+        model.match({ childrens: [] }, { "childrens": { $elemMatch: { name: "Mitsos" } } }).should.equal(false);
+        model.match({ childrens: [] }, { "childrens": { $elemMatch: {} } }).should.equal(false);
+      });
+
+      it('Can use more complex comparisons inside nested query documents', function () {
+        model.match({ childrens: [ { name: "Huey", age: 3 }, { name: "Dewey", age: 7 }, { name: "Louie", age: 12 } ] }, { "childrens": { $elemMatch: { name: "Dewey", age: { $gt: 6, $lt: 8 } } } }).should.equal(true);
+        model.match({ childrens: [ { name: "Huey", age: 3 }, { name: "Dewey", age: 7 }, { name: "Louie", age: 12 } ] }, { "childrens": { $elemMatch: { name: "Dewey", age: { $in: [ 6, 7, 8 ] } } } } ).should.equal(true);
+        model.match({ childrens: [ { name: "Huey", age: 3 }, { name: "Dewey", age: 7 }, { name: "Louie", age: 12 } ] }, { "childrens": { $elemMatch: { name: "Dewey", age: { $gt: 6, $lt: 7 } } } }).should.equal(false);
+        model.match({ childrens: [ { name: "Huey", age: 3 }, { name: "Dewey", age: 7 }, { name: "Louie", age: 12 } ] }, { "childrens": { $elemMatch: { name: "Louie", age: { $gt: 6, $lte: 7 } } } }).should.equal(false);
+      });
     });