-# Copyright (c) 2009, 2010 Nicira Networks
+# Copyright (c) 2009, 2010, 2011 Nicira Networks
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
self.version = version
self.tables = tables
+ # "isRoot" was not part of the original schema definition. Before it
+ # was added, there was no support for garbage collection. So, for
+ # backward compatibility, if the root set is empty then assume that
+ # every table is in the root set.
+ if self.__root_set_size() == 0:
+ for table in self.tables.itervalues():
+ table.is_root = True
+
# Validate that all ref_tables refer to the names of tables
# that exist.
+ #
+ # Also force certain columns to be persistent, as explained in
+ # __check_ref_table(). This requires 'is_root' to be known, so this
+ # must follow the loop updating 'is_root' above.
for table in self.tables.itervalues():
for column in table.columns.itervalues():
self.__check_ref_table(column, column.type.key, "key")
self.__check_ref_table(column, column.type.value, "value")
+ def __root_set_size(self):
+ """Returns the number of tables in the schema's root set."""
+ n_root = 0
+ for table in self.tables.itervalues():
+ if table.is_root:
+ n_root += 1
+ return n_root
+
@staticmethod
def from_json(json):
parser = ovs.db.parser.Parser(json, "database schema")
return DbSchema(name, version, tables)
def to_json(self):
+ # "isRoot" was not part of the original schema definition. Before it
+ # was added, there was no support for garbage collection. So, for
+ # backward compatibility, if every table is in the root set then do not
+ # output "isRoot" in table schemas.
+ default_is_root = self.__root_set_size() == len(self.tables)
+
tables = {}
for table in self.tables.itervalues():
- tables[table.name] = table.to_json()
+ tables[table.name] = table.to_json(default_is_root)
json = {"name": self.name, "tables": tables}
if self.version:
json["version"] = self.version
return json
def __check_ref_table(self, column, base, base_name):
- if (base and base.type == types.UuidType and base.ref_table and
- base.ref_table not in self.tables):
+ if not base or base.type != types.UuidType or not base.ref_table:
+ return
+
+ ref_table = self.tables.get(base.ref_table)
+ if not ref_table:
raise error.Error("column %s %s refers to undefined table %s"
% (column.name, base_name, base.ref_table),
tag="syntax error")
+ if base.is_strong_ref() and not ref_table.is_root:
+ # We cannot allow a strong reference to a non-root table to be
+ # ephemeral: if it is the only reference to a row, then replaying
+ # the database log from disk will cause the referenced row to be
+ # deleted, even though it did exist in memory. If there are
+ # references to that row later in the log (to modify it, to delete
+ # it, or just to point to it), then this will yield a transaction
+ # error.
+ column.persistent = True
+
class IdlSchema(DbSchema):
def __init__(self, name, version, tables, idlPrefix, idlHeader):
DbSchema.__init__(self, name, version, tables)
idlPrefix, idlHeader)
class TableSchema(object):
- def __init__(self, name, columns, mutable=True, max_rows=sys.maxint):
+ def __init__(self, name, columns, mutable=True, max_rows=sys.maxint,
+ is_root=True):
self.name = name
self.columns = columns
self.mutable = mutable
- self.max_rows = max_rows
+ self.max_rows = max_rows
+ self.is_root = is_root
@staticmethod
def from_json(json, name):
columnsJson = parser.get("columns", [dict])
mutable = parser.get_optional("mutable", [bool], True)
max_rows = parser.get_optional("maxRows", [int])
+ is_root = parser.get_optional("isRoot", [bool], False)
parser.finish()
if max_rows == None:
columns[columnName] = ColumnSchema.from_json(columnJson,
columnName)
- return TableSchema(name, columns, mutable, max_rows)
+ return TableSchema(name, columns, mutable, max_rows, is_root)
- def to_json(self):
+ def to_json(self, default_is_root=False):
+ """Returns this table schema serialized into JSON.
+
+ The "isRoot" member is included in the JSON only if its value would
+ differ from 'default_is_root'. Ordinarily 'default_is_root' should be
+ false, because ordinarily a table would be not be part of the root set
+ if its "isRoot" member is omitted. However, garbage collection was not
+ orginally included in OVSDB, so in older schemas that do not include
+ any "isRoot" members, every table is implicitly part of the root set.
+ To serialize such a schema in a way that can be read by older OVSDB
+ tools, specify 'default_is_root' as True.
+ """
json = {}
if not self.mutable:
json["mutable"] = False
+ if default_is_root != self.is_root:
+ json["isRoot"] = self.is_root
json["columns"] = columns = {}
for column in self.columns.itervalues():