From 64be8f29d5a9892047ac40d9306015ac402b1a39 Mon Sep 17 00:00:00 2001 From: Russell Keith-Magee Date: Tue, 9 Jun 2009 12:59:41 +0000 Subject: [PATCH] Fixed #9253 -- Modified the method used to generate constraint names so that it is consistent regardless of machine word size. NOTE: This change is backwards incompatible for some users. If you are using a 32-bit platform, you will observe no differences as a result of this change. However, users on 64-bit platforms may experience some problems using the `reset` management command. Prior to this change, 64-bit platforms would generate a 64-bit, 16 character digest in the constraint name; for example: ALTER TABLE `myapp_sometable` ADD CONSTRAINT `object_id_refs_id_5e8f10c132091d1e` FOREIGN KEY ... Following this change, all platforms, regardless of word size, will generate a 32-bit, 8 character digest in the constraint name; for example: ALTER TABLE `myapp_sometable` ADD CONSTRAINT `object_id_refs_id_32091d1e` FOREIGN KEY ... As a result of this change, you will not be able to use the `reset` management command on any table created with 64-bit constraints. This is because the the new generated name will not match the historically generated name; as a result, the SQL constructed by the `reset` command will be invalid. If you need to reset an application that was created with 64-bit constraints, you will need to manually drop the old constraint prior to invoking `reset`. git-svn-id: http://code.djangoproject.com/svn/django/trunk@10966 bcc190cf-cafb-0310-a4f2-bffc1f526a37 --- django/db/backends/creation.py | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/django/db/backends/creation.py b/django/db/backends/creation.py index f6041c73f3..53874f9f73 100644 --- a/django/db/backends/creation.py +++ b/django/db/backends/creation.py @@ -25,6 +25,10 @@ class BaseDatabaseCreation(object): def __init__(self, connection): self.connection = connection + def _digest(self, *args): + "Generate a 32 bit digest of a set of arguments that can be used to shorten identifying names" + return '%x' % (abs(hash(args)) % (1<<32)) + def sql_create_model(self, model, style, known_models=set()): """ Returns the SQL required to create a single model, as a tuple of: @@ -128,7 +132,7 @@ class BaseDatabaseCreation(object): col = opts.get_field(f.rel.field_name).column # For MySQL, r_name must be unique in the first 64 characters. # So we are careful with character usage here. - r_name = '%s_refs_%s_%x' % (r_col, col, abs(hash((r_table, table)))) + r_name = '%s_refs_%s_%s' % (r_col, col, self._digest(r_table, table)) final_output.append(style.SQL_KEYWORD('ALTER TABLE') + ' %s ADD CONSTRAINT %s FOREIGN KEY (%s) REFERENCES %s (%s)%s;' % \ (qn(r_table), qn(truncate_name(r_name, self.connection.ops.max_name_length())), qn(r_col), qn(table), qn(col), @@ -187,8 +191,7 @@ class BaseDatabaseCreation(object): output.append('\n'.join(table_output)) for r_table, r_col, table, col in deferred: - r_name = '%s_refs_%s_%x' % (r_col, col, - abs(hash((r_table, table)))) + r_name = '%s_refs_%s_%s' % (r_col, col, self._digest(r_table, table)) output.append(style.SQL_KEYWORD('ALTER TABLE') + ' %s ADD CONSTRAINT %s FOREIGN KEY (%s) REFERENCES %s (%s)%s;' % (qn(r_table), qn(truncate_name(r_name, self.connection.ops.max_name_length())), @@ -289,7 +292,7 @@ class BaseDatabaseCreation(object): col = f.column r_table = model._meta.db_table r_col = model._meta.get_field(f.rel.field_name).column - r_name = '%s_refs_%s_%x' % (col, r_col, abs(hash((table, r_table)))) + r_name = '%s_refs_%s_%s' % (col, r_col, self._digest(table, r_table)) output.append('%s %s %s %s;' % \ (style.SQL_KEYWORD('ALTER TABLE'), style.SQL_TABLE(qn(table)),