BigQuery:基于列拆分表

Question

简短问题:我想根据列的不同值将一个BQ表拆分为多个小表。因此，如果列country有10个不同的值，它应该将表拆分为10个单独的表，每个表都有各自的country数据。最好是从BQ查询中完成(使用INSERT、MERGE等)。

我现在正在做的是将数据导入到gstorage ->本地存储->中，在本地执行拆分，然后推送到表中(这是一个非常耗时的过程)。

谢谢。

Answer 1

如果数据具有相同的模式，只需将其保留在一个表中，并使用集群特性：https://cloud.google.com/bigquery/docs/reference/standard-sql/data-definition-language#creating_a_clustered_table

#standardSQL
 CREATE TABLE mydataset.myclusteredtable
 PARTITION BY dateCol
 CLUSTER BY country
 OPTIONS (
   description="a table clustered by country"
 ) AS (
   SELECT ....
 )

https://cloud.google.com/bigquery/docs/clustered-tables

不过，该功能仍处于测试阶段。

Answer 2

为此，您可以使用Dataflow。This answer给出了一个管道示例，该管道查询BigQuery表，根据列拆分行，然后将它们输出到不同的PubSub主题(可以是不同的BigQuery表)：

Pipeline p = Pipeline.create(PipelineOptionsFactory.fromArgs(args).withValidation().create());

PCollection<TableRow> weatherData = p.apply(
        BigQueryIO.Read.named("ReadWeatherStations").from("clouddataflow-readonly:samples.weather_stations"));

final TupleTag<String> readings2010 = new TupleTag<String>() {
};
final TupleTag<String> readings2000plus = new TupleTag<String>() {
};
final TupleTag<String> readingsOld = new TupleTag<String>() {
};

PCollectionTuple collectionTuple = weatherData.apply(ParDo.named("tablerow2string")
        .withOutputTags(readings2010, TupleTagList.of(readings2000plus).and(readingsOld))
        .of(new DoFn<TableRow, String>() {
            @Override
            public void processElement(DoFn<TableRow, String>.ProcessContext c) throws Exception {

                if (c.element().getF().get(2).getV().equals("2010")) {
                    c.output(c.element().toString());
                } else if (Integer.parseInt(c.element().getF().get(2).getV().toString()) > 2000) {
                    c.sideOutput(readings2000plus, c.element().toString());
                } else {
                    c.sideOutput(readingsOld, c.element().toString());
                }

            }
        }));
collectionTuple.get(readings2010)
        .apply(PubsubIO.Write.named("WriteToPubsub1").topic("projects/fh-dataflow/topics/bq2pubsub-topic1"));
collectionTuple.get(readings2000plus)
        .apply(PubsubIO.Write.named("WriteToPubsub2").topic("projects/fh-dataflow/topics/bq2pubsub-topic2"));
collectionTuple.get(readingsOld)
        .apply(PubsubIO.Write.named("WriteToPubsub3").topic("projects/fh-dataflow/topics/bq2pubsub-topic3"));

p.run();