[multi-db] Added postgresql-specific SchemaBuilder subclass that includes method for sequence resets.

git-svn-id: http://code.djangoproject.com/svn/django/branches/multiple-db-support@3442 bcc190cf-cafb-0310-a4f2-bffc1f526a37

1 files changed, 41 insertions, 0 deletions

diff --git a/django/db/backends/postgresql/sql.py b/django/db/backends/postgresql/sql.py
new file mode 100644
index 0000000000..efba646956
--- /dev/null
+++ b/django/db/backends/postgresql/sql.py
@@ -0,0 +1,41 @@
+from django.db import models
+from django.db.backends.ansi.sql import BoundStatement, SchemaBuilder, \
+    default_style
+
+class PgSchemaBuilder(SchemaBuilder):
+    """SchemaBuilder for postgres. Implements an additional method that
+    outputs SQL statements to reset the sequence(s) for a model.
+    """
+    def get_sequence_reset(self, model, style=None):
+        """Get sequence reset sql for a model.
+        """
+        if style is None:
+            style=default_style
+        for f in model._meta.fields:
+            output = []
+            db = model._default_manager.db
+            connection = db.connection
+            qn = db.backend.quote_name
+            if isinstance(f, models.AutoField):
+                output.append(BoundStatement(
+                        "%s setval('%s', (%s max(%s) %s %s));" % \
+                        (style.SQL_KEYWORD('SELECT'),
+                         style.SQL_FIELD('%s_%s_seq' %
+                                         (model._meta.db_table, f.column)),
+                         style.SQL_KEYWORD('SELECT'),
+                         style.SQL_FIELD(qn(f.column)),
+                         style.SQL_KEYWORD('FROM'),
+                         style.SQL_TABLE(qn(model._meta.db_table))),
+                        connection))
+                break # Only one AutoField is allowed per model, so don't bother continuing.
+        for f in model._meta.many_to_many:
+            output.append(
+                BoundStatement("%s setval('%s', (%s max(%s) %s %s));" % \
+                               (style.SQL_KEYWORD('SELECT'),
+                                style.SQL_FIELD('%s_id_seq' % f.m2m_db_table()),
+                                style.SQL_KEYWORD('SELECT'),
+                                style.SQL_FIELD(qn('id')),
+                                style.SQL_KEYWORD('FROM'),
+                                style.SQL_TABLE(f.m2m_db_table())),
+                               connection))
+        return output