PartialResultSet
import type { PartialResultSet } from "https://googleapis.deno.dev/v1/spanner:v1.ts";
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.
§Properties
If true, then the final value in values is chunked, and must be combined
with more values from subsequent PartialResultSet
s to obtain a complete
field value.
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.
Metadata about the result set, such as row type information. Only present in the first response.
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 request for this transaction.
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.
Query plan and execution statistics for the statement that produced this streaming result set. These can be requested by setting 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.
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. Most values are encoded
based on type as described here. 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
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".