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PartialResultSet(mapping=None, *, ignore_unknown_fields=False, **kwargs)
Partial results from a streaming read or SQL query. Streaming reads and SQL queries better tolerate large result sets, large rows, and large values, but are a little trickier to consume.
Attributes |
|
---|---|
Name | Description |
metadata |
google.cloud.spanner_v1.types.ResultSetMetadata
Metadata about the result set, such as row type information. Only present in the first response. |
values |
MutableSequence[google.protobuf.struct_pb2.Value]
A streamed result set consists of a stream of values, which might be split into many PartialResultSet messages to
accommodate large rows and/or large values. Every N complete
values defines a row, where N is equal to the number of
entries in
metadata.row_type.fields][google.spanner.v1.StructType.fields] .
Most values are encoded based on type as described
here][google.spanner.v1.TypeCode] .
It's possible that the last value in values is "chunked",
meaning that the rest of the value is sent in subsequent
PartialResultSet \ (s). This is denoted by the
chunked_value][google.spanner.v1.PartialResultSet.chunked_value]
field. Two or more chunked values can be merged to form a
complete value as follows:
- bool/number/null : can't be chunked
- string : concatenate the strings
- list : concatenate the lists. If the last element in a
list is a string , list , or object , merge it
with the first element in the next list by applying these
rules recursively.
- object : concatenate the (field name, field value)
pairs. If a field name is duplicated, then apply these
rules recursively to merge the field values.
Some examples of merging:
::
Strings are concatenated.
"foo", "bar" => "foobar"
Lists of non-strings are concatenated.
[2, 3], [4] => [2, 3, 4]
Lists are concatenated, but the last and first elements are merged
because they are strings.
["a", "b"], ["c", "d"] => ["a", "bc", "d"]
Lists are concatenated, but the last and first elements are merged
because they are lists. Recursively, the last and first elements
of the inner lists are merged because they are strings.
["a", ["b", "c"]], [["d"], "e"] => ["a", ["b", "cd"], "e"]
Non-overlapping object fields are combined.
{"a": "1"}, {"b": "2"} => {"a": "1", "b": 2"}
Overlapping object fields are merged.
{"a": "1"}, {"a": "2"} => {"a": "12"}
Examples of merging objects containing lists of strings.
{"a": ["1"]}, {"a": ["2"]} => {"a": ["12"]}
For a more complete example, suppose a streaming SQL query
is yielding a result set whose rows contain a single string
field. The following PartialResultSet \ s might be
yielded:
::
{
"metadata": { ... }
"values": ["Hello", "W"]
"chunked_value": true
"resume_token": "Af65..."
}
{
"values": ["orl"]
"chunked_value": true
}
{
"values": ["d"]
"resume_token": "Zx1B..."
}
This sequence of PartialResultSet \ s encodes two rows,
one containing the field value "Hello" , and a second
containing the field value "World" = "W" + "orl" + "d" .
Not all PartialResultSet \ s contain a resume_token .
Execution can only be resumed from a previously yielded
resume_token . For the above sequence of
PartialResultSet \ s, resuming the query with
"resume_token": "Af65..." yields results from the
PartialResultSet with value "orl".
|
chunked_value |
bool
If true, then the final value in values][google.spanner.v1.PartialResultSet.values] is
chunked, and must be combined with more values from
subsequent PartialResultSet \ s to obtain a complete
field value.
|
resume_token |
bytes
Streaming calls might be interrupted for a variety of reasons, such as TCP connection loss. If this occurs, the stream of results can be resumed by re-sending the original request and including resume_token . Note that executing
any other transaction in the same session invalidates the
token.
|
stats |
google.cloud.spanner_v1.types.ResultSetStats
Query plan and execution statistics for the statement that produced this streaming result set. These can be requested by setting ExecuteSqlRequest.query_mode][google.spanner.v1.ExecuteSqlRequest.query_mode]
and are sent only once with the last response in the stream.
This field is also present in the last response for DML
statements.
|
precommit_token |
google.cloud.spanner_v1.types.MultiplexedSessionPrecommitToken
Optional. A precommit token is included if the read-write transaction has multiplexed sessions enabled. Pass the precommit token with the highest sequence number from this transaction attempt to the Commit][google.spanner.v1.Spanner.Commit] request for this
transaction.
|
last |
bool
Optional. Indicates whether this is the last PartialResultSet in the stream. The server might
optionally set this field. Clients shouldn't rely on this
field being set in all cases.
|