#!/usr/bin/env python # # Copyright 2007 Google Inc. # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. # """Primitives for dealing with datastore indexes. Example index.yaml file: ------------------------ indexes: - kind: Cat ancestor: no properties: - name: name - name: age direction: desc - kind: Cat properties: - name: name direction: ascending - name: whiskers direction: descending - kind: Store ancestor: yes properties: - name: business direction: asc - name: owner direction: asc """ from google.appengine.api import datastore_types from google.appengine.api import validation from google.appengine.api import yaml_errors from google.appengine.api import yaml_object from google.appengine.datastore import datastore_pb from google.appengine.datastore import entity_pb class Property(validation.Validated): """Representation for an individual property of an index. Attributes: name: Name of attribute to sort by. direction: Direction of sort. """ ATTRIBUTES = { 'name': validation.TYPE_STR, 'direction': validation.Options(('asc', ('ascending',)), ('desc', ('descending',)), default='asc'), } class Index(validation.Validated): """Individual index definition. Order of the properties properties determins a given indixes sort priority. Attributes: kind: Datastore kind that index belongs to. ancestors: Include ancestors in index. properties: Properties to sort on. """ ATTRIBUTES = { 'kind': validation.TYPE_STR, 'ancestor': validation.Type(bool, default=False), 'properties': validation.Optional(validation.Repeated(Property)), } class IndexDefinitions(validation.Validated): """Top level for index definition file. Attributes: indexes: List of Index definitions. """ ATTRIBUTES = { 'indexes': validation.Optional(validation.Repeated(Index)), } def ParseIndexDefinitions(document): """Parse an individual index definitions document from string or stream. Args: document: Yaml document as a string or file-like stream. Raises: EmptyConfigurationFile when the configuration file is empty. MultipleConfigurationFile when the configuration file contains more than one document. Returns: Single parsed yaml file if one is defined, else None. """ try: return yaml_object.BuildSingleObject(IndexDefinitions, document) except yaml_errors.EmptyConfigurationFile: return None def ParseMultipleIndexDefinitions(document): """Parse multiple index definitions documents from a string or stream. Args: document: Yaml document as a string or file-like stream. Returns: A list of datstore_index.IndexDefinitions objects, one for each document. """ return yaml_object.BuildObjects(IndexDefinitions, document) def IndexDefinitionsToKeys(indexes): """Convert IndexDefinitions to set of keys. Args: indexes: A datastore_index.IndexDefinitions instance, or None. Returns: A set of keys constructed from the argument, each key being a tuple of the form (kind, ancestor, properties) where properties is a tuple of (name, direction) pairs, direction being ASCENDING or DESCENDING (the enums). """ keyset = set() if indexes is not None: if indexes.indexes: for index in indexes.indexes: keyset.add(IndexToKey(index)) return keyset def IndexToKey(index): """Convert Index to key. Args: index: A datastore_index.Index instance (not None!). Returns: A tuple of the form (kind, ancestor, properties) where properties is a tuple of (name, direction) pairs, direction being ASCENDING or DESCENDING (the enums). """ props = [] if index.properties is not None: for prop in index.properties: if prop.direction == 'asc': direction = ASCENDING else: direction = DESCENDING props.append((prop.name, direction)) return index.kind, index.ancestor, tuple(props) ASCENDING = datastore_pb.Query_Order.ASCENDING DESCENDING = datastore_pb.Query_Order.DESCENDING EQUALITY_OPERATORS = set((datastore_pb.Query_Filter.EQUAL, )) INEQUALITY_OPERATORS = set((datastore_pb.Query_Filter.LESS_THAN, datastore_pb.Query_Filter.LESS_THAN_OR_EQUAL, datastore_pb.Query_Filter.GREATER_THAN, datastore_pb.Query_Filter.GREATER_THAN_OR_EQUAL, )) EXISTS_OPERATORS = set((datastore_pb.Query_Filter.EXISTS, )) _DIRECTION_MAP = { 'asc': entity_pb.Index_Property.ASCENDING, 'ascending': entity_pb.Index_Property.ASCENDING, 'desc': entity_pb.Index_Property.DESCENDING, 'descending': entity_pb.Index_Property.DESCENDING, } def Normalize(filters, orders): """ Normalizes filter and order query components. The resulting components have the same effect as the given components if used in a query. Returns: (filter, orders) the reduced set of filters and orders """ eq_properties = set() inequality_properties = set() for f in filters: if f.op() == datastore_pb.Query_Filter.IN and f.property_size() == 1: f.set_op(datastore_pb.Query_Filter.EQUAL) if f.op() in EQUALITY_OPERATORS: eq_properties.add(f.property(0).name()) elif f.op() in INEQUALITY_OPERATORS: inequality_properties.add(f.property(0).name()) eq_properties -= inequality_properties remove_set = eq_properties.copy() new_orders = [] for o in orders: if o.property() not in remove_set: remove_set.add(o.property()) new_orders.append(o) orders = new_orders if datastore_types._KEY_SPECIAL_PROPERTY in eq_properties: orders = [] new_orders = [] for o in orders: if o.property() == datastore_types._KEY_SPECIAL_PROPERTY: new_orders.append(o) break new_orders.append(o) orders = new_orders return (filters, orders) def RemoveNativelySupportedComponents(filters, orders): """ Removes query components that are natively supported by the datastore. The resulting filters and orders should not be used in an actual query. Returns (filters, orders) the reduced set of filters and orders """ (filters, orders) = Normalize(filters, orders) has_key_desc_order = False if orders and orders[-1].property() == datastore_types._KEY_SPECIAL_PROPERTY: if orders[-1].direction() == ASCENDING: orders = orders[:-1] else: has_key_desc_order = True if not has_key_desc_order: for f in filters: if (f.op() in INEQUALITY_OPERATORS and f.property(0).name() != datastore_types._KEY_SPECIAL_PROPERTY): break else: filters = [f for f in filters if f.property(0).name() != datastore_types._KEY_SPECIAL_PROPERTY] return (filters, orders) def CompositeIndexForQuery(query): """Return the composite index needed for a query. A query is translated into a tuple, as follows: - The first item is the kind string, or None if we're not filtering on kind (see below). - The second item is a bool giving whether the query specifies an ancestor. - After that come (property, ASCENDING) pairs for those Filter entries whose operator is EQUAL or IN. Since the order of these doesn't matter, they are sorted by property name to normalize them in order to avoid duplicates. - After that comes at most one (property, ASCENDING) pair for a Filter entry whose operator is on of the four inequalities. There can be at most one of these. - After that come all the (property, direction) pairs for the Order entries, in the order given in the query. Exceptions: (a) if there is a Filter entry with an inequality operator that matches the first Order entry, the first order pair is omitted (or, equivalently, in this case the inequality pair is omitted). (b) if an Order entry corresponds to an equality filter, it is ignored (since there will only ever be one value returned). (c) if there is an equality filter on __key__ all orders are dropped (since there will be at most one result returned). (d) if there is an order on __key__ all further orders are dropped (since keys are unique). (e) orders on __key__ ASCENDING are dropped (since this is supported natively by the datastore). - Finally, if there are Filter entries whose operator is EXISTS, and whose property names are not already listed, they are added, with the direction set to ASCENDING. This algorithm should consume all Filter and Order entries. Additional notes: - The low-level implementation allows queries that don't specify a kind; but the Python API doesn't support this yet. - If there's an inequality filter and one or more sort orders, the first sort order *must* match the inequality filter. - The following indexes are always built in and should be suppressed: - query on kind only; - query on kind and one filter *or* one order; - query on ancestor only, without kind (not exposed in Python yet); - query on kind and equality filters only, no order (with or without ancestor). - While the protocol buffer allows a Filter to contain multiple properties, we don't use this. It is only needed for the IN operator but this is (currently) handled on the client side, so in practice each Filter is expected to have exactly one property. Args: query: A datastore_pb.Query instance. Returns: A tuple of the form (required, kind, ancestor, (prop1, prop2, ...), neq): required: boolean, whether the index is required kind: the kind or None; ancestor: True if this is an ancestor query; prop1, prop2, ...: tuples of the form (name, direction) where: name: a property name; direction: datastore_pb.Query_Order.ASCENDING or ...DESCENDING; neq: the number of prop tuples corresponding to equality filters. """ required = True kind = query.kind() ancestor = query.has_ancestor() filters = query.filter_list() orders = query.order_list() for filter in filters: assert filter.op() != datastore_pb.Query_Filter.IN, 'Filter.op()==IN' nprops = len(filter.property_list()) assert nprops == 1, 'Filter has %s properties, expected 1' % nprops if not kind: required = False (filters, orders) = RemoveNativelySupportedComponents(filters, orders) eq_filters = [f for f in filters if f.op() in EQUALITY_OPERATORS] ineq_filters = [f for f in filters if f.op() in INEQUALITY_OPERATORS] exists_filters = [f for f in filters if f.op() in EXISTS_OPERATORS] assert (len(eq_filters) + len(ineq_filters) + len(exists_filters)) == len(filters), 'Not all filters used' if (kind and not ineq_filters and not exists_filters and not orders): names = set(f.property(0).name() for f in eq_filters) if not names.intersection(datastore_types._SPECIAL_PROPERTIES): required = False ineq_property = None if ineq_filters: ineq_property = ineq_filters[0].property(0).name() for filter in ineq_filters: assert filter.property(0).name() == ineq_property props = [] for f in eq_filters: prop = f.property(0) props.append((prop.name(), ASCENDING)) props.sort() if ineq_property: if orders: assert ineq_property == orders[0].property() else: props.append((ineq_property, ASCENDING)) for order in orders: props.append((order.property(), order.direction())) for filter in exists_filters: prop = filter.property(0) prop_name = prop.name() for name, direction in props: if name == prop_name: break else: props.append((prop_name, ASCENDING)) if kind and not ancestor and len(props) <= 1: required = False if props: prop, dir = props[0] if prop in datastore_types._SPECIAL_PROPERTIES and dir is DESCENDING: required = True return (required, kind, ancestor, tuple(props), len(eq_filters)) def IndexYamlForQuery(kind, ancestor, props): """Return the composite index definition YAML needed for a query. The arguments are the same as the tuples returned by CompositeIndexForQuery, without the last neq element. Args: kind: the kind or None ancestor: True if this is an ancestor query, False otherwise prop1, prop2, ...: tuples of the form (name, direction) where: name: a property name; direction: datastore_pb.Query_Order.ASCENDING or ...DESCENDING; Returns: A string with the YAML for the composite index needed by the query. """ yaml = [] yaml.append('- kind: %s' % kind) if ancestor: yaml.append(' ancestor: yes') if props: yaml.append(' properties:') for name, direction in props: yaml.append(' - name: %s' % name) if direction == DESCENDING: yaml.append(' direction: desc') return '\n'.join(yaml) def IndexDefinitionToProto(app_id, index_definition): """Transform individual Index definition to protocol buffer. Args: app_id: Application id for new protocol buffer CompositeIndex. index_definition: datastore_index.Index object to transform. Returns: New entity_pb.CompositeIndex with default values set and index information filled in. """ proto = entity_pb.CompositeIndex() proto.set_app_id(app_id) proto.set_id(0) proto.set_state(entity_pb.CompositeIndex.WRITE_ONLY) definition_proto = proto.mutable_definition() definition_proto.set_entity_type(index_definition.kind) definition_proto.set_ancestor(index_definition.ancestor) if index_definition.properties is not None: for prop in index_definition.properties: prop_proto = definition_proto.add_property() prop_proto.set_name(prop.name) prop_proto.set_direction(_DIRECTION_MAP[prop.direction]) return proto def IndexDefinitionsToProtos(app_id, index_definitions): """Transform multiple index definitions to composite index records Args: app_id: Application id for new protocol buffer CompositeIndex. index_definition: A list of datastore_index.Index objects to transform. Returns: A list of tranformed entity_pb.Compositeindex entities with default values set and index information filled in. """ return [IndexDefinitionToProto(app_id, index) for index in index_definitions] def ProtoToIndexDefinition(proto): """Transform individual index protocol buffer to index definition. Args: proto: An instance of entity_pb.CompositeIndex to transform. Returns: A new instance of datastore_index.Index. """ properties = [] proto_index = proto.definition() for prop_proto in proto_index.property_list(): prop_definition = Property(name=prop_proto.name()) if prop_proto.direction() == entity_pb.Index_Property.DESCENDING: prop_definition.direction = 'descending' properties.append(prop_definition) index = Index(kind=proto_index.entity_type(), properties=properties) if proto_index.ancestor(): index.ancestor = True return index def ProtosToIndexDefinitions(protos): """Transform multiple index protocol buffers to index definitions. Args: A list of entity_pb.Index records. """ return [ProtoToIndexDefinition(definition) for definition in protos]