Python 3.9 is now generally available.

google.appengine.api.datastore.Query

A datastore query.

Inherits From: expected_type

(Instead of this, consider using appengine.ext.gql.Query! It provides a query language interface on top of the same functionality.)

Queries are used to retrieve entities that match certain criteria, including app id, kind, and property filters. Results may also be sorted by properties.

App id and kind are required. Only entities from the given app, of the given type, are returned. If an ancestor is set, with Ancestor(), only entities with that ancestor are returned.

Property filters are used to provide criteria based on individual property values. A filter compares a specific property in each entity to a given value or list of possible values.

An entity is returned if its property values match all of the query's filters. In other words, filters are combined with AND, not OR. If an entity does not have a value for a property used in a filter, it is not returned.

Property filters map filter strings of the form ' ' to filter values. Use dictionary accessors to set property filters, like so:

> query = Query('Person') > query['name ='] = 'Ryan' > query['age >='] = 21

This query returns all Person entities where the name property is 'Ryan' and the age property is at least 21.

Another way to build this query is:

> query = Query('Person') > query.update({'name =': 'Ryan', 'age >=': 21})

The supported operators are =, >, <, >=, and <=. Only one inequality filter may be used per query. Any number of equals filters may be used in a single Query.

A filter value may be a list or tuple of values. This is interpreted as multiple filters with the same filter string and different values, all ANDed together. For example, this query returns everyone with the tags "google" and "app engine":

> Query('Person', {'tag =': ('google', 'app engine')})

Result entities can be returned in different orders. Use the Order() method to specify properties that results will be sorted by, and in which direction.

Note that filters and orderings may be provided at any time before the query is run. When the query is fully specified, Run() runs the query and returns an iterator. The query results can be accessed through the iterator.

A query object may be reused after it's been run. Its filters and orderings can be changed to create a modified query.

If you know how many result entities you need, use Get() to fetch them:

> query = Query('Person', {'age >': 21}) > for person in query.Get(4): > print 'I have four pints left. Have one on me, %s!' % person['name']

If you don't know how many results you need, or if you need them all, you can get an iterator over the results by calling Run():

> for person in Query('Person', {'age >': 21}).Run(): > print 'Have a pint on me, %s!' % person['name']

Get() is more efficient than Run(), so use Get() whenever possible.

Finally, the Count() method returns the number of result entities matched by the query. The returned count is cached; successive Count() calls will not re-scan the datastore unless the query is changed.

namespace string, the namespace to query.
kind string, the kind of entities to query, or None.
filters dict, initial set of filters.
keys_only boolean, if keys should be returned instead of entities.
projection iterable of property names to project.
distinct boolean, if projection should be distinct.
compile boolean, if the query should generate cursors.
cursor datastore_query.Cursor, the start cursor to use.
end_cursor datastore_query.Cursor, the end cursor to use.
_namespace deprecated, use namespace instead.

Methods

Ancestor

View source

Sets an ancestor for this query.

This restricts the query to only return result entities that are descended from a given entity. In other words, all of the results will have the ancestor as their parent, or parent's parent, or etc.

Raises BadArgumentError or BadKeyError if parent is not an existing Entity or Key in the datastore.

Args

the key must be complete

ancestor Entity or Key

Returns

this query

Query

Count

View source

Returns the number of entities that this query matches.

Args
limit, a number or None. If there are more results than this, stop short and just return this number. Providing this argument makes the count operation more efficient.
config Optional Configuration to use for this request.

Returns
The number of results.

Get

View source

Deprecated, use list(Run(...)) instead.

Args
limit int or long representing the maximum number of entities to return.
offset int or long representing the number of entities to skip
kwargs Any keyword arguments accepted by datastore_query.QueryOptions().

Returns

a list of entities

[Entity, ...]

GetBatcher

View source

Runs this query and returns a datastore_query.Batcher.

This is not intended to be used by application developers. Use Get() instead!

Args
config Optional Configuration to use for this request.

Returns

an iterator that provides access to the query results

Iterator

GetCompiledCursor

View source

Get the cursor from the last run of this query.

The source of this cursor varies depending on what the last call was:

  • Run: A cursor that points immediately after the last result pulled off the returned iterator.
  • Get: A cursor that points immediately after the last result in the returned list.
  • Count: A cursor that points immediately after the last result counted.

Returns
A datastore_query.Cursor object that can be used in subsequent query requests.

Raises
AssertionError The query has not yet been run or cannot be compiled.

GetCompiledQuery

View source

Returns the internal-only pb representation of the last query run.

Do not use.

Raises
AssertionError Query not compiled or not yet executed.

GetCursor

View source

Get the cursor from the last run of this query.

The source of this cursor varies depending on what the last call was:

  • Run: A cursor that points immediately after the last result pulled off the returned iterator.
  • Get: A cursor that points immediately after the last result in the returned list.
  • Count: A cursor that points immediately after the last result counted.

Returns
A datastore_query.Cursor object that can be used in subsequent query requests.

Raises
AssertionError The query has not yet been run or cannot be compiled.

GetDistinct

View source

Returns True if the current instance is distinct.

Returns
A boolean indicating if the distinct flag is set.

GetFilterPredicate

View source

Returns a datastore_query.FilterPredicate for the current instance.

Returns
datastore_query.FilterPredicate or None if no filters are set on the current Query.

GetIndexList

View source

Get the index list from the last run of this query.

Returns
A list of indexes used by the last run of this query.

Raises
AssertionError The query has not yet been run.

GetOrder

View source

Gets a datastore_query.Order for the current instance.

Returns
datastore_query.Order or None if there are no sort orders set on the current Query.

GetQuery

View source

Returns a datastore_query.Query for the current instance.

GetQueryOptions

View source

Returns a datastore_query.QueryOptions for the current instance.

Hint

View source

Sets a hint for how this query should run.

The query hint gives us information about how best to execute your query. Currently, we can only do one index scan, so the query hint should be used to indicates which index we should scan against.

Use FILTER_FIRST if your first filter will only match a few results. In this case, it will be most efficient to scan against the index for this property, load the results into memory, and apply the remaining filters and sort orders there.

Similarly, use ANCESTOR_FIRST if the query's ancestor only has a few descendants. In this case, it will be most efficient to scan all entities below the ancestor and load them into memory first.

Use ORDER_FIRST if the query has a sort order and the result set is large or you only plan to fetch the first few results. In that case, we shouldn't try to load all of the results into memory; instead, we should scan the index for this property, which is in sorted order.

Note that hints are currently ignored in the v3 datastore!

Arg
one of datastore.Query.[ORDER_FIRST, ANCESTOR_FIRST, FILTER_FIRST]

Returns

this query

Query

IsKeysOnly

View source

Returns True if this query is keys only, False otherwise.

Order

View source

Specify how the query results should be sorted.

Result entities will be sorted by the first property argument, then by the second, and so on. For example, this:

> query = Query('Person') > query.Order('bday', ('age', Query.DESCENDING))

sorts everyone in order of their birthday, starting with January 1. People with the same birthday are sorted by age, oldest to youngest.

The direction for each sort property may be provided; if omitted, it defaults to ascending.

Order() may be called multiple times. Each call resets the sort order from scratch.

If an inequality filter exists in this Query it must be the first property passed to Order. Any number of sort orders may be used after the inequality filter property. Without inequality filters, any number of filters with different orders may be specified.

Entities with multiple values for an order property are sorted by their lowest value.

Note that a sort order implies an existence filter! In other words, Entities without the sort order property are filtered out, and not included in the query results.

If the sort order property has different types in different entities - ie, if bob['id'] is an int and fred['id'] is a string - the entities will be grouped first by the property type, then sorted within type. No attempt is made to compare property values across types.

Raises BadArgumentError if any argument is of the wrong format.

Args

the properties to sort by, in sort order. each argument may be either a

string or (string, direction) 2-tuple.

Returns

this query

Query

Run

View source

Runs this query.

If a filter string is invalid, raises BadFilterError. If a filter value is invalid, raises BadValueError. If an IN filter is provided, and a sort order on another property is provided, raises BadQueryError.

If you know in advance how many results you want, use limit=#. It's more efficient.

Args
kwargs Any keyword arguments accepted by datastore_query.QueryOptions().

Returns

an iterator that provides access to the query results

Iterator

clear

D.clear() -> None. Remove all items from D.

copy

View source

The copy method is not supported.

fromkeys

Create a new dictionary with keys from iterable and values set to value.

get

Return the value for key if key is in the dictionary, else default.

items

D.items() -> a set-like object providing a view on D's items

keys

D.keys() -> a set-like object providing a view on D's keys

pop

D.pop(k[,d]) -> v, remove specified key and return the corresponding value.

If key is not found, default is returned if given, otherwise KeyError is raised

popitem

Remove and return a (key, value) pair as a 2-tuple.

Pairs are returned in LIFO (last-in, first-out) order. Raises KeyError if the dict is empty.

setdefault

View source

If the filter exists, returns its value. Otherwise sets it to value.

If the property name is the empty string or not a string, raises BadPropertyError. If the value is not a supported type, raises BadValueError.

update

View source

Updates this query's filters from the ones in other.

If any filter string is invalid, raises BadFilterError. If any value is not a supported type, raises BadValueError.

values

D.values() -> an object providing a view on D's values

__contains__

True if the dictionary has the specified key, else False.

__eq__

Return self==value.

__ge__

Return self>=value.

__getitem__

x.getitem(y) <==> x[y]

__gt__

Return self>value.

__iter__

View source

Implement iter(self).

__le__

Return self<=value.

__len__

Return len(self).

__lt__

Return self<value.

__ne__

Return self!=value.

__or__

Return self|value.

__ror__

Return value|self.

ANCESTOR_FIRST 2
ASCENDING 1
DESCENDING 2
FILTER_FIRST 3
FILTER_REGEX Instance of re.Pattern
INEQUALITY_OPERATORS

{
 '<',
 '<=',
 '>',
 '>='
}

OPERATORS

{
 '<': 1,
 '<=': 2,
 '=': 5,
 '==': 5,
 '>': 3,
 '>=': 4
}

ORDER_FIRST 1
UPPERBOUND_INEQUALITY_OPERATORS

{
 '<',
 '<='
}