Add basic json query support

Author: zbarbuto

README.md

@@ -369,6 +369,37 @@ See [LoopBack types](http://loopback.io/doc/en/lb3/LoopBack-types.html) for de
 
 For details, see the corresponding [driver issue](https://github.com/brianc/node-pg-types/issues/28).
 
+## Querying JSON fields
+
+**Note** The fields you are querying should be setup to use the JSON postgresql data type - see Defining models
+
+Assuming a model such as this:
+
+```json
+{
+  "name": "Customer",
+  "properties": {
+    "address": {
+      "type": "object",
+      "postgresql": {
+        "dataType": "json"
+      }
+    }
+  }
+}
+```
+
+You can query the nested fields with dot notation:
+
+```javascript
+Customer.find({
+  where: {
+    'address.state': 'California'
+  },
+  order: 'address.city'
+})
+```
+
 ## Discovery and auto-migration
 
 ### Model discovery

lib/postgresql.js

@@ -321,6 +321,37 @@ function escapeLiteral(str) {
   return escaped;
 }
 
+/*
+ * Check if a value is attempting to use nested json keys
+ * @param {String} property The property being queried from where clause
+ * @returns {Boolean} True of the property contains dots for nested json
+ */
+function isNested(property) {
+  return property.split('.').length > 1;
+}
+
+/*
+ * Overwrite the loopback-connector column escape
+ * to allow querying nested json keys
+ * @param {String} model The model name
+ * @param {String} property The property name
+ * @returns {String} The escaped column name, or column with nested keys for deep json columns
+ */
+PostgreSQL.prototype.columnEscaped = function(model, property) {
+  if (isNested(property)) {
+    // Convert column to PostgreSQL json style query: "model"->>'val'
+    var self = this;
+    return property
+      .split('.')
+      .map(function(val, idx) { return (idx === 0 ? self.columnEscaped(model, val) : escapeLiteral(val)); })
+      .reduce(function(prev, next, idx, arr) {
+        return idx == 0 ? next : idx < arr.length - 1 ? prev + '->' + next : prev + '->>' + next;
+      });
+  } else {
+    return this.escapeName(this.column(model, property));
+  }
+};
+
 /*!
  * Escape the name for PostgreSQL DB
  * @param {String} name The name
@@ -499,6 +530,12 @@ PostgreSQL.prototype._buildWhere = function(model, where) {
       // The value is not an array, fall back to regular fields
     }
     var p = props[key];
+
+    if (p == null && isNested(key)) {
+      // See if we are querying nested json
+      p = props[key.split('.')[0]];
+    }
+
     if (p == null) {
       // Unknown property, ignore it
       debug('Unknown property %s is skipped for model %s', key, model);

test/postgresql.test.js

@@ -658,6 +658,86 @@ describe('postgresql connector', function() {
       });
     });
   });
+
+  context('json data type', function() {
+    var Customer;
+
+    before(function(done) {
+      db = getDataSource();
+
+      Customer = db.define('Customer', {
+        address: {
+          type: 'object',
+          postgresql: {
+            dataType: 'json',
+          },
+        },
+      });
+
+      db.automigrate(function(err) {
+        if (err) return done(err);
+        Customer.create([{
+          address: {
+            city: 'Springfield',
+            street: {
+              number: 42,
+            },
+          },
+        }, {
+          address: {
+            city: 'Hill Valley',
+            street: {
+              number: 56,
+            },
+          },
+        }], function(err, customers) {
+          return done(err);
+        });
+      });
+    });
+
+    it('allows querying for nested json properties', function(done) {
+      Customer.find({
+        where: {
+          'address.city': 'Hill Valley',
+        },
+      }, function(err, results) {
+        if (err) return done(err);
+        results.length.should.eql(1);
+        results[0].address.city.should.eql('Hill Valley');
+        done();
+      });
+    });
+
+    it('queries multiple levels of nesting', function(done) {
+      Customer.find({
+        where: {
+          'address.street.number': 56,
+        },
+      }, function(err, results) {
+        if (err) return done(err);
+        results.length.should.eql(1);
+        results[0].address.city.should.eql('Hill Valley');
+        done();
+      });
+    });
+
+    it('allows ordering by nested json properties', function(done) {
+      Customer.find({
+        order: ['address.city DESC'],
+      }, function(err, results1) {
+        if (err) return done(err);
+        results1[0].address.city.should.eql('Springfield');
+        Customer.find({
+          order: ['address.city ASC'],
+        }, function(err, results2) {
+          if (err) return done(err);
+          results2[0].address.city.should.eql('Hill Valley');
+          done();
+        });
+      });
+    });
+  });
 });
 
 describe('Serial properties', function() {