[multi-db] Added preliminary drop-table generation to django.db.backends.ansi.sql.SchemaBuilder.

git-svn-id: http://code.djangoproject.com/svn/django/branches/multiple-db-support@3320 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/backends/ansi/sql.py

@@ -43,8 +43,13 @@ class SchemaBuilder(object):
     or other constraints.
     """
     def __init__(self):
+        # models that I have created
         self.models_already_seen = set()
-
+        # model references, keyed by the referrent model
+        self.references = {}
+        # table cache; set to short-circuit table lookups
+        self.tables = None
+        
     def get_create_table(self, model, style=None):
         """Construct and return the SQL expression(s) needed to create the
         table for the given model, and any constraints on that
@@ -218,8 +223,8 @@ class SchemaBuilder(object):
     def get_drop_table(self, model, cascade=False, style=None):
         """Construct and return the SQL statment(s) needed to drop a model's
         table. If cascade is true, then output additional statments to drop any
-        dependant man-many tables and drop any foreign keys that reference
+        many-to-many tables that this table created and any foreign keys that
-        this table.
+        reference this table.
         """
         if style is None:
             style = default_style
@@ -227,16 +232,45 @@ class SchemaBuilder(object):
         info = opts.connection_info
         db_table = opts.db_table
         backend = info.backend
+        qn = backend.quote_name
         output = []
         output.append(BoundStatement(
                 '%s %s;' % (style.SQL_KEYWORD('DROP TABLE'),
-                            style.SQL_TABLE(backend.quote_name(db_table))),
+                            style.SQL_TABLE(qn(db_table))),
                 info.connection))
 
         if cascade:
-            # FIXME deal with my foreign keys, others that might have a foreign
+            # deal with others that might have a foreign key TO me: alter
-            # key TO me, and many-many
+            # their tables to drop the constraint
-            pass
+            if backend.supports_constraints:
+                references_to_delete = self.get_references()
+                if model in references_to_delete:
+                    for rel_class, f in references_to_delete[model]:
+                        table = rel_class._meta.db_table
+                        if not self.table_exists(info, table):
+                            continue
+                        col = f.column
+                        r_table = opts.db_table
+                        r_col = opts.get_field(f.rel.field_name).column
+                        output.append(BoundStatement(
+                            '%s %s %s %s;' % 
+                            (style.SQL_KEYWORD('ALTER TABLE'),
+                             style.SQL_TABLE(qn(table)),
+                             style.SQL_KEYWORD(
+                                        backend.get_drop_foreignkey_sql()),
+                             style.SQL_FIELD(qn("%s_referencing_%s_%s" %
+                                                (col, r_table, r_col)))),
+                            info.connection))
+                    del references_to_delete[model]
+            # many to many: drop any many-many tables that are my
+            # responsiblity
+            for f in opts.many_to_many:
+                if not isinstance(f.rel, models.GenericRel):
+                    output.append(BoundStatement(
+                            '%s %s;' %
+                            (style.SQL_KEYWORD('DROP TABLE'),
+                             style.SQL_TABLE(qn(f.m2m_db_table()))),
+                            info.connection))
         # Reverse it, to deal with table dependencies.        
         output.reverse()
         return output
@@ -273,11 +307,36 @@ class SchemaBuilder(object):
     def get_initialdata_path(self, model):
         """Get the path from which to load sql initial data files for a model.
         """
-        return os.path.normpath(os.path.join(os.path.dirname(models.get_app(model._meta.app_label).__file__), 'sql'))
+        return os.path.normpath(os.path.join(os.path.dirname(
+                    models.get_app(model._meta.app_label).__file__), 'sql'))
             
     def get_rel_data_type(self, f):
         return (f.get_internal_type() in ('AutoField', 'PositiveIntegerField',
                                           'PositiveSmallIntegerField')) \
                                           and 'IntegerField' \
                                           or f.get_internal_type()
-        
+    
+    def get_references(self):
+        """Fill (if needed) and return the reference cache.
+        """
+        if self.references:
+            return self.references
+        for klass in models.get_models():
+            for f in klass._meta.fields:
+                if f.rel:
+                    self.references.setdefault(f.rel.to, []).append((klass, f))
+        return self.references
+
+    def get_table_list(self, connection_info):
+        """Get list of tables accessible via the connection described by
+        connection_info.
+        """
+        if self.tables is not None:
+            return self.tables
+        cursor = info.connection.cursor()
+        introspection = connection_info.get_introspection_module()
+        return introspection.get_table_list(cursor)        
+    
+    def table_exists(self, connection_info, table):
+        tables = self.get_table_list(connection_info)
+        return table in tables

django/db/models/manager.py

@@ -159,9 +159,8 @@ class Manager(object):
         """Get list of tables accessible via my model's connection.
         """
         info = self.model._meta.connection_info
-        cursor = info.connection.cursor()
+        builder = info.get_creation_module.builder()
-        introspect = info.get_introspection_module()
+        return builder.get_table_list(info)
-        return introspect.get_table_list(cursor)
     
 class ManagerDescriptor(object):
     # This class ensures managers aren't accessible via model instances.

tests/othertests/ansi_sql.py

@@ -1,52 +1,24 @@
-# For Python 2.3
-if not hasattr(__builtins__, 'set'):
-    from sets import Set as set
-
 """
->>> from django.db import models
 >>> from django.db.backends.ansi import sql
 
-# test models
+# so we can test with a predicatable constraint setting
->>> class Car(models.Model):
+>>> real_cnst = Mod._meta.connection_info.backend.supports_constraints
-...     make = models.CharField(maxlength=32)
+>>> Mod._meta.connection_info.backend.supports_constraints = True
-...     model = models.CharField(maxlength=32)
-...     year = models.IntegerField()
-...     condition = models.CharField(maxlength=32)
-...     
-...     class Meta:
-...         app_label = 'ansi_sql'
-
->>> class Collector(models.Model):
-...     name = models.CharField(maxlength=32)
-...     cars = models.ManyToManyField(Car)
-...     
-...     class Meta:
-...         app_label = 'ansi_sql'
-
->>> class Mod(models.Model):
-...     car = models.ForeignKey(Car)
-...     part = models.CharField(maxlength=32, db_index=True)
-...     description = models.TextField()
-...     
-...     class Meta:
-...         app_label = 'ansi_sql'
     
 # generate create sql
 >>> builder = sql.SchemaBuilder()
 >>> builder.get_create_table(Car)
-([BoundStatement('CREATE TABLE "ansi_sql_car" (...);')], [])
+([BoundStatement('CREATE TABLE "ansi_sql_car" (...);')], {})
 >>> builder.models_already_seen
-[<class 'othertests.ansi_sql.Car'>]
+Set([<class 'othertests.ansi_sql.Car'>])
 >>> builder.models_already_seen = set()
 
 # test that styles are used
 >>> builder.get_create_table(Car, style=mockstyle())
-([BoundStatement('SQL_KEYWORD(CREATE TABLE) SQL_TABLE("ansi_sql_car") (...SQL_FIELD("id")...);')], [])
+([BoundStatement('SQL_KEYWORD(CREATE TABLE) SQL_TABLE("ansi_sql_car") (...SQL_FIELD("id")...);')], {})
 
 # test pending relationships
 >>> builder.models_already_seen = set()
->>> real_cnst = Mod._meta.connection_info.backend.supports_constraints
->>> Mod._meta.connection_info.backend.supports_constraints = True
 >>> builder.get_create_table(Mod)
 ([BoundStatement('CREATE TABLE "ansi_sql_mod" (..."car_id" integer NOT NULL,...);')], {<class 'othertests.ansi_sql.Car'>: [BoundStatement('ALTER TABLE "ansi_sql_mod" ADD CONSTRAINT ... FOREIGN KEY ("car_id") REFERENCES "ansi_sql_car" ("id");')]})
 >>> builder.models_already_seen = set()
@@ -54,7 +26,6 @@ if not hasattr(__builtins__, 'set'):
 ([BoundStatement('CREATE TABLE "ansi_sql_car" (...);')], {})
 >>> builder.get_create_table(Mod)
 ([BoundStatement('CREATE TABLE "ansi_sql_mod" (..."car_id" integer NOT NULL REFERENCES "ansi_sql_car" ("id"),...);')], {})
->>> Mod._meta.connection_info.backend.supports_constraints = real_cnst
 
 # test many-many
 >>> builder.get_create_table(Collector)
@@ -75,16 +46,82 @@ if not hasattr(__builtins__, 'set'):
 >>> builder.get_initialdata_path = othertests_sql
 >>> builder.get_initialdata(Car)
 [BoundStatement('insert into ansi_sql_car (...)...values (...);')]
+
+# test drop
+>>> builder.get_drop_table(Mod)
+[BoundStatement('DROP TABLE "ansi_sql_mod";')]
+>>> builder.get_drop_table(Mod, cascade=True)
+[BoundStatement('DROP TABLE "ansi_sql_mod";')]
+>>> builder.get_drop_table(Car)
+[BoundStatement('DROP TABLE "ansi_sql_car";')]
+>>> builder.get_drop_table(Car, cascade=True)
+[BoundStatement('DROP TABLE "ansi_sql_car";')]
+
+>>> builder.tables = ['ansi_sql_car', 'ansi_sql_mod', 'ansi_sql_collector']
+>>> Mod._meta.connection_info.backend.supports_constraints = False
+>>> builder.get_drop_table(Car, cascade=True)
+[BoundStatement('DROP TABLE "ansi_sql_car";')]
+>>> Mod._meta.connection_info.backend.supports_constraints = True
+>>> builder.get_drop_table(Car, cascade=True)
+[BoundStatement('ALTER TABLE "ansi_sql_mod" ...'), BoundStatement('DROP TABLE "ansi_sql_car";')]
+>>> builder.get_drop_table(Collector)
+[BoundStatement('DROP TABLE "ansi_sql_collector";')]
+>>> builder.get_drop_table(Collector, cascade=True)
+[BoundStatement('DROP TABLE "ansi_sql_collector_cars";'), BoundStatement('DROP TABLE "ansi_sql_collector";')]
+>>> Mod._meta.connection_info.backend.supports_constraints = real_cnst
+
 """
 import os
+from django.db import models
+from django.core.management import install
+
+# For Python 2.3
+if not hasattr(__builtins__, 'set'):
+    from sets import Set as set
+
+
+# test models
+class Car(models.Model):
+    make = models.CharField(maxlength=32)
+    model = models.CharField(maxlength=32)
+    year = models.IntegerField()
+    condition = models.CharField(maxlength=32)
+    
+    class Meta:
+        app_label = 'ansi_sql'
+
+        
+class Collector(models.Model):
+    name = models.CharField(maxlength=32)
+    cars = models.ManyToManyField(Car)
+    
+    class Meta:
+        app_label = 'ansi_sql'
+
+        
+class Mod(models.Model):
+    car = models.ForeignKey(Car)
+    part = models.CharField(maxlength=32, db_index=True)
+    description = models.TextField()
+    
+    class Meta:
+        app_label = 'ansi_sql'
+
 
-# mock style that wraps text in STYLE(text), for testing
 class mockstyle:
+    """mock style that wraps text in STYLE(text), for testing"""
     def __getattr__(self, attr):
         if attr in ('ERROR', 'ERROR_OUTPUT', 'SQL_FIELD', 'SQL_COLTYPE',
                     'SQL_KEYWORD', 'SQL_TABLE'):
             return lambda text: "%s(%s)" % (attr, text)
 
+        
 def othertests_sql(mod):
     """Look in othertests/sql for sql initialdata"""
     return os.path.normpath(os.path.join(os.path.dirname(__file__), 'sql'))
+
+
+# install my stuff
+Car.objects.install()
+Collector.objects.install()
+Mod.objects.install()