[PATCH 3/6] Adding afe custom database engine

[Lucas Meneghel Rodrigues <lmr@redhat.com>]

Turns out that we rely on custom code to generate
joins that does some trickery with Django ORM system,
and was using a method calling get_from_clause, that
was present on the Query class on Django 1.1. Now,
the method was moved to a class upper in the hierarchy,
called SQLCompiler, and SQLCompiler is tied to the db
backend being used. After some research, seems like there's
no solution cleaner than implementing one db backend
special for autotest, just to accomodate this function.

So created one db engine that inherits pretty much everything
from the mysql one, except for the compiler classes.

Tested, and it works fairly well. Eventually more work
needs to be put in getting the web app into better shape.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
---
 frontend/db/backends/afe/base.py          |   22 +++++++++++++++++++
 frontend/db/backends/afe/compiler.py      |   32 +++++++++++++++++++++++++++++
 frontend/db/backends/afe/creation.py      |    1 +
 frontend/db/backends/afe/introspection.py |    1 +
 frontend/db/backends/afe/validation.py    |    1 +
 5 files changed, 57 insertions(+), 0 deletions(-)
 create mode 100644 frontend/db/__init__.py
 create mode 100644 frontend/db/backends/__init__.py
 create mode 100644 frontend/db/backends/afe/__init__.py
 create mode 100644 frontend/db/backends/afe/base.py
 create mode 100644 frontend/db/backends/afe/compiler.py
 create mode 100644 frontend/db/backends/afe/creation.py
 create mode 100644 frontend/db/backends/afe/introspection.py
 create mode 100644 frontend/db/backends/afe/validation.py

diff --git a/frontend/db/__init__.py b/frontend/db/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/frontend/db/backends/__init__.py b/frontend/db/backends/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/frontend/db/backends/afe/__init__.py b/frontend/db/backends/afe/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/frontend/db/backends/afe/base.py b/frontend/db/backends/afe/base.py
new file mode 100644
index 0000000..6d617d2
--- /dev/null
+++ b/frontend/db/backends/afe/base.py
@@ -0,0 +1,22 @@
+from django.db.backends.mysql.base import DatabaseCreation as MySQLCreation
+from django.db.backends.mysql.base import DatabaseOperations as MySQLOperations
+from django.db.backends.mysql.base import DatabaseWrapper as MySQLDatabaseWrapper
+from django.db.backends.mysql.base import DatabaseIntrospection as MySQLIntrospection
+
+try:
+    import MySQLdb as Database
+except ImportError, e:
+    from django.core.exceptions import ImproperlyConfigured
+    raise ImproperlyConfigured("Error loading MySQLdb module: %s" % e)
+
+
+class DatabaseOperations(MySQLOperations):
+    compiler_module = "autotest_lib.frontend.db.backends.afe.compiler"
+
+
+class DatabaseWrapper(MySQLDatabaseWrapper):
+    def __init__(self, *args, **kwargs):
+        super(DatabaseWrapper, self).__init__(*args, **kwargs)
+        self.creation = MySQLCreation(self)
+        self.ops = DatabaseOperations()
+        self.introspection = MySQLIntrospection(self)
diff --git a/frontend/db/backends/afe/compiler.py b/frontend/db/backends/afe/compiler.py
new file mode 100644
index 0000000..9971415
--- /dev/null
+++ b/frontend/db/backends/afe/compiler.py
@@ -0,0 +1,32 @@
+from django.db.backends.mysql import compiler as mysql_compiler
+from autotest_lib.frontend.afe.model_logic import _quote_name
+
+class SQLCompiler(mysql_compiler.SQLCompiler):
+    def get_from_clause(self):
+        from_, params = super(SQLCompiler, self).get_from_clause()
+
+        if hasattr(self.query, "_custom_joins"):
+            for join_dict in self.query._custom_joins:
+                from_.append('%s %s AS %s ON (%s)'
+                             % (join_dict['join_type'],
+                                _quote_name(join_dict['table']),
+                                _quote_name(join_dict['alias']),
+                                join_dict['condition']))
+                params.extend(join_dict['condition_values'])
+
+        return from_, params
+
+class SQLInsertCompiler(mysql_compiler.SQLInsertCompiler, SQLCompiler):
+    pass
+
+class SQLDeleteCompiler(mysql_compiler.SQLDeleteCompiler, SQLCompiler):
+    pass
+
+class SQLUpdateCompiler(mysql_compiler.SQLUpdateCompiler, SQLCompiler):
+    pass
+
+class SQLAggregateCompiler(mysql_compiler.SQLAggregateCompiler, SQLCompiler):
+    pass
+
+class SQLDateCompiler(mysql_compiler.SQLDateCompiler, SQLCompiler):
+    pass
diff --git a/frontend/db/backends/afe/creation.py b/frontend/db/backends/afe/creation.py
new file mode 100644
index 0000000..955a11e
--- /dev/null
+++ b/frontend/db/backends/afe/creation.py
@@ -0,0 +1 @@
+from django.db.backends.mysql.creation import *
diff --git a/frontend/db/backends/afe/introspection.py b/frontend/db/backends/afe/introspection.py
new file mode 100644
index 0000000..222bc9b
--- /dev/null
+++ b/frontend/db/backends/afe/introspection.py
@@ -0,0 +1 @@
+from django.db.backends.mysql.introspection import *
diff --git a/frontend/db/backends/afe/validation.py b/frontend/db/backends/afe/validation.py
new file mode 100644
index 0000000..818b34a
--- /dev/null
+++ b/frontend/db/backends/afe/validation.py
@@ -0,0 +1 @@
+from django.db.backends.mysql.validation import *
-- 
1.7.5.2