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.
Metadata about the result set, such as row type information. Only present in the first response.
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 will also be 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 is 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
: cannot 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..."
will yield results from the
PartialResultSet
with value ["orl"]
.