Fixes Issue 15: case insensitive mysql short code search takes very long

1. fix bug when getting latest short code using order by link.id
2. fix bug when comparing two short code using collate

README.md

@@ -1,8 +1,8 @@
+<p align="center"><img src="src/pyui/static/logo/logov2.png" alt="pygmy" height="200px"></p>
+
 Pygmy
 =====
 
-<p align="center"><img src="src/pyui/static/logo/logov2.png" alt="pygmy" height="200px"></p>
-
 [![Build Status](https://travis-ci.org/amitt001/pygmy.svg?branch=master)](https://travis-ci.org/amitt001/pygmy) [![Coverage Status](https://coveralls.io/repos/github/amitt001/pygmy/badge.svg?branch=master)](https://coveralls.io/github/amitt001/pygmy?branch=master) [![Requirements Status](https://requires.io/github/amitt001/pygmy/requirements.svg?branch=master)](https://requires.io/github/amitt001/pygmy/requirements/?branch=master)
 
 Live version of this project @ [https://pygy.co](https://pygy.co)
@@ -90,20 +90,26 @@ DB Setup:
 Use MySQL
 ---------
 
+First install `pymysql`:
+
 `pip install pymysql`
 
 Check correct port:
 
 `mysqladmin variables | grep port`
 
-Enter below line in src/pygmy/core/pygmy.cfg fro database->url value
+Change below line in `src/pygmy/core/pygmy.cfg`:
 
-`mysql+pymysql://root:root@127.0.0.1:3306/pygmy`
+```
+engine: mysql
+url: mysql+pymysql://root:root@127.0.0.1:3306/pygmy
+```
 
 Enter MySQL URL
 
 `CREATE DATABASE pygmy;`
 
+Note: Better using Mysql with version > `5.6.5` to use default value of `CURRENT_TIMESTAMP` for `DATETIME`.
 
 Use Postgresql
 --------------

src/pygmy/database/factory.py

@@ -2,6 +2,7 @@
 from pygmy.config import config
 from pygmy.database.sqlite import SqliteDatabase
 from pygmy.database.postgresql import PostgreSQLDatabase
+from pygmy.database.mysql import MySQLDatabase
 from pygmy.database.base import Model
 
 
@@ -15,6 +16,8 @@ def create():
             database = SqliteDatabase()
         elif config.database['engine'] == 'postgresql':
             database = PostgreSQLDatabase()
+        elif config.database['engine'] == 'mysql':
+            database = MySQLDatabase()
         else:
             raise Exception(
                 "Unsupported DB type. Supported types are "

src/pygmy/database/mysql.py

@@ -0,0 +1,5 @@
+from pygmy.database.base import BaseDatabase
+
+
+class MySQLDatabase(BaseDatabase):
+    pass

src/pygmy/model/link.py

@@ -2,7 +2,7 @@
 import binascii
 import datetime
 
-from sqlalchemy import event, and_, or_
+from sqlalchemy import event, and_, or_, DDL
 from sqlalchemy.exc import IntegrityError
 from sqlalchemy.orm import relationship
 from sqlalchemy import (Column, String, Integer, Boolean,
@@ -67,6 +67,17 @@ def generate_short_code(_, connection, target):
 
 event.listen(Link, 'after_insert', Link.generate_short_code)
 
+# adding event to modify field `short_code` when using mysql
+event.listen(
+    Link.__table__,
+    "after_create",
+    DDL(
+        "alter table {table} modify short_code varchar(6) "
+        "CHARACTER SET utf8 COLLATE utf8_bin default null".format(
+            table=Link.__tablename__
+        )
+    ).execute_if(dialect='mysql')
+)
 
 class LinkManager:
     """Link model manager"""
@@ -244,7 +255,7 @@ def latest_default_link(self, db):
             Link.is_custom.is_(False),
             Link.short_code.isnot(None),
             Link.short_code != ''
-        )).order_by(Link.created_at.desc()).first()
+        )).order_by(Link.id.desc()).first()
 
     @dbconnection
     def find(self, db, **kwargs):