creating a branch to do partial index with sequelize migration

lib/dialects/abstract/query-generator.js

@@ -548,7 +548,8 @@ module.exports = (function() {
         'ON', this.quoteIdentifiers(tableName),
         this._dialect.supports.index.using === 2 && options.using ? 'USING ' + options.using : '',
         '(' + fieldsSql.join(', ') + (options.operator ? ' '+options.operator : '') + ')',
-        (this._dialect.supports.index.parser && options.parser ? 'WITH PARSER ' + options.parser : undefined)
+        (this._dialect.supports.index.parser && options.parser ? 'WITH PARSER ' + options.parser : undefined),
+        (this._dialect.supports.index.where && options.where ? 'WHERE ' + Utils.smartWhere(options.where) : undefined)
       ]).join(' ');
     },
 

lib/dialects/postgres/index.js

@@ -37,6 +37,7 @@ PostgresDialect.prototype.supports = _.merge(_.cloneDeep(Abstract.prototype.supp
   index: {
     concurrently: true,
     using: 2,
+    where: true
   },
   JSON: true,
   JSONB: true