Cfrgtkky

I am trying to copy datastore entities to a PostgreSQL instance. As I don't need each fields, I performed projections following this snippet. I build the following query:

public static Query DatastoreQuery() {

    Query.Builder query = Query.newBuilder();



    // Add filter

    query.addKindBuilder().setName("FOO");

    query.setFilter(makeFilter("bar", PropertyFilter.Operator.EQUAL, makeValue("fuz")));



    // Add projections

    query.addProjection(Projection.newBuilder().setProperty(PropertyReference.newBuilder().setName("createdAt")));



    return query.build();

}

This query is then used in the pipeline:

pipeline.apply(DatastoreIO.v1().read().withProjectId(options.getProjectId())

            .withQuery(ExtractDatastore.DatastoreQuery()));

Following Unable to addProjection to relation field in envers query, I am expecting to get a Map<String, Object>. I would like to follow Apache Beam documentation to insert the entities in PostgreSQL, using a code similar to:

.apply(JdbcIO.<Map<String, Object>>write()      

    .withDataSourceConfiguration(JdbcIO.DataSourceConfiguration.create(

        "com.google.cloud.sql.postgres",

        jdbcUrl

    )

.withUsername(username)

.withPassword(password))

.withQuery("<INSERT QUERY>")

.withPreparedStatementSetter(<this is what needs to be filled>));

As I have found no examples, here are my questions are the following:

1) How to handle the elements from the query ? In the example of my projection, how do I get access to createdAt which is a timestamp ? In python, I did it with : value.timestamp_value.ToDatetime(). Is there an equivalent in Java ?

2) Are the entities really under the format <Map<String, Object>> as described in the SO issue ?

2) Can one apply JdbcIO.write() to Map<String, Object> or does it require to be under the <KV<KeyType, ValueType>> format as described in the small snippet of the documentation ?

I am grateful to take any inputs on this topic.