google.appengine.ext.db.GqlQuery

A Query class that uses GQL query syntax instead of .filter() etc.

Inherits From: expected_type

google.appengine.ext.db.GqlQuery(
    query_string, *args, **kwds
)

query_string Properly formatted GQL query string.
*args Positional arguments used to bind numeric references in the query.
**kwds Dictionary-based arguments for named references.

PropertyError if the query filters or sorts on a property that's not indexed.

Methods

bind

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bind(
    *args, **kwds
)

Bind arguments (positional or keyword) to the query.

Note that you can also pass arguments directly to the query constructor. Each time you call bind() the previous set of arguments is replaced with the new set. This is useful because the hard work in in parsing the query; so if you expect to be using the same query with different sets of arguments, you should hold on to the GqlQuery() object and call bind() on it each time.

Args
*args Positional arguments used to bind numeric references in the query.
**kwds Dictionary-based arguments for named references.

count

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count(
    limit=1000, **kwargs
)

Number of entities this query fetches.

Beware: count() ignores the LIMIT clause on GQL queries.

Args
limit A number. If there are more results than this, stop short and just return this number. Providing this argument makes the count operation more efficient.
kwargs Any keyword arguments accepted by datastore_query.QueryOptions().

Returns
Number of entities this query fetches.

cursor

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cursor()

Get a serialized cursor for an already executed query.

The returned cursor effectively lets a future invocation of a similar query to begin fetching results immediately after the last returned result from this query invocation.

Returns
A base64-encoded serialized cursor.

Raises
AssertionError If the query has not been executed.

fetch

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fetch(
    limit, offset=0, **kwargs
)

Return a list of items selected using SQL-like limit and offset.

Always use run(limit=...) instead of fetch() when iterating over a query.

Beware: offset must read and discard all skipped entities. Use cursor()/with_cursor() instead.

Args
limit Maximum number of results to return.
offset Optional number of results to skip first; default zero.
kwargs Any keyword arguments accepted by datastore_query.QueryOptions().

Returns
A list of db.Model instances. There may be fewer than 'limit' results if there aren't enough results to satisfy the request.

get

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get(
    **kwargs
)

Get first result from this.

Beware: get() ignores the LIMIT clause on GQL queries.

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

Returns
First result from running the query if there are any, else None.

index_list

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index_list()

Get the index list for an already executed query.

Returns
A list of indexes used by the query.

Raises
AssertionError If the query has not been executed.

is_distinct

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is_distinct()

Returns true if the projection query should be distinct.

This is equivalent to the SQL syntax: SELECT DISTINCT. It is only available for projection queries, it is not valid to specify distinct without also specifying projection properties.

Distinct projection queries on entities with multi-valued properties will return the same entity multiple times, once for each unique combination of properties included in the projection.

Returns
True if this projection query is distinct.

is_keys_only

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is_keys_only()

Returns whether this query is keys only.

Returns
True if this query returns keys, False if it returns entities.

projection

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projection()

Returns the tuple of properties in the projection or None.

Projected results differ from normal results in multiple ways:

  • they only contain a portion of the original entity and cannot be put;
  • properties defined on the model, but not included in the projections will have a value of None, even if the property is required or has a default value;
  • multi-valued properties (such as a ListProperty) will only contain a single value.
  • dynamic properties not included in the projection will not appear on the model instance.
  • dynamic properties included in the projection are deserialized into their indexed type. Specifically one of str, bool, long, float, GeoPt, Key or User. If the original type is known, it can be restored using datastore_types.RestoreFromIndexValue.

However, projection queries are significantly faster than normal queries.

Projection queries on entities with multi-valued properties will return the same entity multiple times, once for each unique combination of values for properties included in the order, an inequality property, or the projected properties.

Returns
The list of properties in the projection, or None if no projection is set on this query.

run

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run(
    **kwargs
)

Iterator for this query that handles the LIMIT clause property.

If the GQL query string contains a LIMIT clause, this function fetches all results before returning an iterator. Otherwise results are retrieved in batches by the iterator.

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

Returns
Iterator for this query.

with_cursor

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with_cursor(
    start_cursor=None, end_cursor=None
)

Set the start and end of this query using serialized cursors.

Conceptually cursors point to the position between the last result returned and the next result so running a query with each of the following cursors combinations will return all results in four chunks with no duplicate results:

query.with_cursor(end_cursor=cursor1) query.with_cursors(cursor1, cursor2) query.with_cursors(cursor2, cursor3) query.with_cursors(start_cursor=cursor3)

For example if the cursors pointed to: cursor: 1 2 3 result: a b c d e f g h

The results returned by these queries would be [a, b], [c, d], [e, f], [g, h] respectively.

Cursors are pinned to the position just after the previous result (last result, exclusive), so if results are inserted or deleted between the time the cursor was made and these queries are executed, the cursors stay pinned to these positions. For example:

delete(b, f, g, h) put(a1, b1, c1, d1) cursor: 1(b) 2(d) 3(f) result: a a1 b1 c c1 d d1 e

The results returned by these queries would now be: [a, a1], [b1, c, c1, d], [d1, e], [] respectively.

Args
start_cursor The cursor position at which to start or None
end_cursor The cursor position at which to end or None

Returns
This Query instance, for chaining.

Raises
BadValueError when cursor is not valid.

__getitem__

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__getitem__(
    arg
)

Support for query[index] and query[start:stop].

Beware: this ignores the LIMIT clause on GQL queries.

Args
arg Either a single integer, corresponding to the query[index] syntax, or a Python slice object, corresponding to the query[start:stop] or query[start:stop:step] syntax.

Returns
A single Model instance when the argument is a single integer. A list of Model instances when the argument is a slice.

__iter__

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__iter__()

Iterator for this query.

If you know the number of results you need, consider fetch() instead, or use a GQL query with a LIMIT clause. It's more efficient.