Tested and documented comparedb update

docs/index.rst

@@ -57,24 +57,6 @@ Options for upgradedb
   `./manage.py upgradedb --seed 005` will skip migrations 000 to 005 but not
   006.
 
-
-Configuration for comparedb
----------------------------
-
-The `comparedb` command is available only for Postgres. It executes a few raw
-postgres shell commands which you might need to customize to add user
-credentials, encoding or specify database templates. This can be done through
-the `NASHVEGAS` dictionnary in your setting::
-
-    NASHVEGAS = {
-        "createdb": "createdb -U postgres -T template0 -E UTF8",
-        "dropdb": "dropdb -U postgres",
-        "pg_dump": "pg_dump -U postgres",
-    }
-
-By default, nashvegas executes raw `createdb`, `dropdb` or `pg_dump` commands.
-
-
 Conventions
 -----------
 
@@ -110,6 +92,100 @@ product codes on next release::
             product.code = "NEW-%s" % product.code
             product.save()
 
+Configuration for comparedb
+---------------------------
+
+The `comparedb` command is available only for advanced system administrators.
+It proceeds as such:
+
+* get the SQL structure dump of the current database
+* create a new database, the "compare" database
+* syncdb in the "compare" database,
+* get the SQL structure dump of the "compare" database
+* output the diff
+
+It executes a few raw shell commands which you might need to customize to add
+user credentials, encoding or specify database templates. This can be done
+through the `NASHVEGAS` dictionnary in your setting.
+
+Example for PostgreSQL
+``````````````````````
+
+By default, nashvegas executes raw `createdb`, `dropdb` or `pg_dump` commands,
+example customisation::
+
+    NASHVEGAS = {
+        "createdb": "createdb -U postgres -T template0 -E UTF8 {dbname}",
+        "dropdb": "dropdb -U postgres {dbname}",
+        "dumpdb": "pg_dump -U postgres {dbname}",
+    }
+
+
+If you add a field "test" on model "Foo", comparedb will output::
+
+    >>> ./manage.py comparedb
+    Getting schema for current database...
+    Getting schema for fresh database...
+    Outputing diff between the two...
+    --- 
+    +++ 
+    @@ -515,7 +515,8 @@
+
+     CREATE TABLE testapp_foo (
+         id integer NOT NULL,
+    -    bar character varying(100)
+    +    bar character varying(100),
+    +    test character varying(100)
+     );
+
+Example for MySQL
+`````````````````
+
+MySQL is not supported by default thought such settings do work::
+
+    NASHVEGAS = { 
+        "createdb": "mysql -u root -p -e \"create database {dbname}\"",
+        "dropdb": "mysql -u root -p -e \"drop database {dbname}\"",
+        "dumpdb": "mysqldump -u root -p {dbname}",
+    }
+
+If you add a field "test" on model "Foo", comparedb will output::
+
+    >>> ./manage.py comparedb       
+    Getting schema for current database...
+    Enter password: 
+    Getting schema for fresh database...
+    Enter password: 
+    Enter password: 
+    Enter password: 
+    Outputing diff between the two...
+    --- 
+    +++ 
+    @@ -1,6 +1,6 @@
+     -- MySQL dump 10.13  Distrib 5.1.58, for debian-linux-gnu (x86_64)
+     --
+    --- Host: localhost    Database: testproject
+    +-- Host: localhost    Database: testproject_compare
+     -- ------------------------------------------------------
+     -- Server version  5.1.58-1ubuntu1
+
+    @@ -419,6 +419,7 @@
+     CREATE TABLE `testapp_foo` (
+       `id` int(11) NOT NULL AUTO_INCREMENT,
+       `bar` varchar(100) DEFAULT NULL,
+    +  `test` varchar(100) DEFAULT NULL,
+       PRIMARY KEY (`id`)
+     ) ENGINE=MyISAM DEFAULT CHARSET=latin1;
+     /*!40101 SET character_set_client = @saved_cs_client */;
+    @@ -441,4 +442,4 @@
+     /*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;
+     /*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;
+
+    --- Dump completed on 2012-03-07 12:58:15
+    +-- Dump completed on 2012-03-07 12:58:18
+
+Typicall customisation would be to setup a `$HOME/.my.cnf` that contains
+credentials allowing to run this command without password prompt.
 
 Indices and tables
 ==================

nashvegas/management/commands/comparedb.py

@@ -9,7 +9,7 @@
 from django.core.management.base import BaseCommand
 
 
-NASHVEGAS = getattr(settings, "NASHVEGAS", None)
+NASHVEGAS = getattr(settings, "NASHVEGAS", {})
 
 
 class Command(BaseCommand):
@@ -24,16 +24,12 @@ class Command(BaseCommand):
     help = "Compares current database with the one that nashvegas will build from scratch."
 
     def setup_database(self):
-        command = "createdb %s" % self.name
-        if NASHVEGAS and "createdb" in settings.NASHVEGAS:
-            command = "%s %s" % (settings.NASHVEGAS["createdb"], self.name)
-        Popen(command.split()).wait()
+        command = NASHVEGAS.get("createdb", "createdb {dbname}")
+        Popen(command.format(dbname=self.compare_name), shell=True).wait()
 
     def teardown_database(self):
-        command = "dropdb %s" % self.name
-        if NASHVEGAS and "dropdb" in settings.NASHVEGAS:
-            command = "%s %s" % (settings.NASHVEGAS["dropdb"], self.name)
-        Popen(command.split()).wait()
+        command = NASHVEGAS.get("dropdb", "dropdb {dbname}")
+        Popen(command.format(dbname=self.compare_name), shell=True).wait()
 
     def handle(self, *args, **options):
         """
@@ -44,30 +40,26 @@ def handle(self, *args, **options):
         report the diffs to the user.
         """
         self.db = options.get("database", DEFAULT_DB_ALIAS)
-        self.name = options.get("db_name")
-        if not self.name:
-            self.name = "%s_compare" % connections.databases[self.db]["NAME"]
-
-        command = "pg_dump -s %s" % connections[self.db].settings_dict["NAME"]
-        if NASHVEGAS and "pg_dump" in settings.NASHVEGAS:
-            command = "%s -s %s" % (settings.NASHVEGAS["pg_dump"], 
-                connections[self.db].settings_dict["NAME"])
-
+        self.current_name = connections[self.db].settings_dict["NAME"]
+        self.compare_name = options.get("db_name")
+        if not self.compare_name:
+            self.compare_name = "%s_compare" % self.current_name
+
+        command = NASHVEGAS.get("dumpdb", "pg_dump -s {dbname}")
+
         print "Getting schema for current database..."
-        print command
-        current_sql = Popen(command.split(), stdout=PIPE).stdout.readlines()
+        current_sql = Popen(command.format(dbname=self.current_name),
+            shell=True, stdout=PIPE).stdout.readlines()
 
         print "Getting schema for fresh database..."
         self.setup_database()
-        orig = connections[self.db].settings_dict["NAME"]
         connections[self.db].close()
-        connections[self.db].settings_dict["NAME"] = self.name
+        connections[self.db].settings_dict["NAME"] = self.compare_name
         call_command("syncdb", interactive=False, verbosity=0)
-        print command
-        new_sql = Popen(command.split() + ["-s", self.name], 
+        new_sql = Popen(command.format(dbname=self.compare_name).split(), 
             stdout=PIPE).stdout.readlines()
         connections[self.db].close()
-        connections[self.db].settings_dict["NAME"] = orig
+        connections[self.db].settings_dict["NAME"] = self.current_name
         self.teardown_database()
 
         print "Outputing diff between the two..."