Added some migrations

WARNING: Still not ready for production — schema version needs incrementing, and testing still required

supysonic/schema/migration/mysql/20181010.py

@@ -0,0 +1,24 @@
+import argparse
+from supysonic import db
+try:
+    import MySQLdb as provider
+except ImportError:
+    import pymysql as provider
+
+parser = argparse.ArgumentParser()
+parser.add_argument('username')
+parser.add_argument('password')
+parser.add_argument('database')
+parser.add_argument('-H', '--host', default = 'localhost', help = 'default: localhost')
+args = parser.parse_args()
+
+with provider.connect(host = args.host, user = args.username, passwd = args.password, db = args.database) as conn:
+    c = conn.cursor()
+    c.execute('ALTER TABLE track ADD COLUMN has_art BOOLEAN NOT NULL DEFAULT false')
+
+    art = dict()
+	c.execute('SELECT path FROM track')
+    for row in c:
+        art[row[0]] = bool(db.Track._extract_cover_art(row[0].encode('utf-8')))
+    c.executemany('UPDATE track SET has_art=? WHERE path=?', [ (a, p) for p, a in art.items() ])
+    conn.commit()

supysonic/schema/migration/postgres/20181010.py

@@ -0,0 +1,21 @@
+import argparse
+import psycopg2
+from supysonic import db
+
+parser = argparse.ArgumentParser()
+parser.add_argument('username')
+parser.add_argument('password')
+parser.add_argument('database')
+parser.add_argument('-H', '--host', default = 'localhost', help = 'default: localhost')
+args = parser.parse_args()
+
+with psycopg2.connect(host = args.host, user = args.username, password = args.password, dbname = args.database) as conn:
+    c = conn.cursor()
+    c.execute('ALTER TABLE track ADD COLUMN has_art BOOLEAN NOT NULL DEFAULT false')
+
+    art = dict()
+    c.execute('SELECT path FROM track')
+    for row in c.fetchall():
+        art[row[0]] = bool(db.Track._extract_cover_art(row[0].encode('utf-8')))
+    c.executemany('UPDATE track SET has_art=%s WHERE path=%s', [ (a, p) for p, a in art.items() ])
+    conn.commit()

supysonic/schema/migration/sqlite/20181010.py

@@ -0,0 +1,18 @@
+import argparse
+import sqlite3
+from supysonic import db
+
+parser = argparse.ArgumentParser()
+parser.add_argument('dbfile', help = 'Path to the SQLite database file')
+args = parser.parse_args()
+
+with sqlite3.connect(args.dbfile) as conn:
+    c = conn.cursor()
+    c.execute('ALTER TABLE track ADD COLUMN has_art BOOLEAN NOT NULL DEFAULT false')
+
+    art = dict()
+    for row in c.execute('SELECT path FROM track'):
+        art[row[0]] = bool(db.Track._extract_cover_art(row[0].encode('utf-8')))
+    c.executemany('UPDATE track SET has_art=? WHERE path=?', [ (a, p) for p, a in art.items() ])
+    conn.commit()
+    conn.execute('VACUUM')