piotr-szuberski commented on a change in pull request #12611:
URL: https://github.com/apache/beam/pull/12611#discussion_r501676146
##########
File path:
sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/spanner/SpannerIO.java
##########
@@ -678,6 +703,42 @@ public Read withPartitionOptions(PartitionOptions
partitionOptions) {
.withTransaction(getTransaction());
return input.apply(Create.of(getReadOperation())).apply("Execute query",
readAll);
}
+
+ SerializableFunction<Struct, Row> getFormatFn() {
+ return (SerializableFunction<Struct, Row>)
+ input ->
+ Row.withSchema(Schema.builder().addInt64Field("Key").build())
+ .withFieldValue("Key", 3L)
+ .build();
+ }
+ }
+
+ public static class ReadRows extends PTransform<PBegin, PCollection<Row>> {
+ Read read;
+ Schema schema;
+
+ public ReadRows(Read read, Schema schema) {
+ super("Read rows");
+ this.read = read;
+ this.schema = schema;
Review comment:
Thank you @nielm ! I thought about the LIMIT approach but then I found
the same arguments not to do that.
It appears there exist a jdbc client for Spanner:
https://cloud.google.com/spanner/docs/jdbc-drivers . I'll try to figure out if
I can use it.
There is ResultSetMetadata in Spanner's REST API which extends json object.
https://cloud.google.com/spanner/docs/reference/rest/v1/ResultSetMetadata but
at the end of the day it requires at least partially to fetch the data.
But I would leave it for another PR as it supposedly require to move
SchemaUtils from io/jdbc to some more general place (extensions/sql?). As I can
see Struct type is mapped to String/Varchar as is mentioned in the FAQ, so it
may not be the best option
```
The Cloud Spanner STRUCT data type is mapped to a SQL VARCHAR data type,
accessible through
this driver as String types. All other types have appropriate mappings.
```
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