user21627820
user21627820

Reputation: 1

Apache Beam IOElasticsearchIO.read() method (Java), which expects a PBegin input and a means to handle a collection of queries

I'm running into an issue using the ElasticsearchIO.read() to handle more than one instance of a query. My queries are being dynamically built as a PCollection based on an incoming group of values. I'm trying to see how to load the .withQuery() parameter which could provide this capability or any approach that provides flexibility.

The issue is that ElasticsearchIO.read() method expects a PBegin input to start a pipeline, but it seems like I need access outside of a pipeline context somehow. PBegin represents the beginning of a pipeline, and it's required to create a pipeline that can read data from Elasticsearch using IOElasticsearchIO.read().

Can I wrap the ElasticsearchIO.read() call in a Create transform that creates a PCollection with a single element (e.g., PBegin) to simulate the beginning of a pipeline or something similar?

Here is my naive attempt without accepting the reality of PBegin:

   PCollection<String> queries = ... // a PCollection of Elasticsearch queries
    
    PCollection<String> queryResults = queries.apply(
        ParDo.of(new DoFn<String, String>() {
            @ProcessElement
            public void processElement(ProcessContext c) {
                String query = c.element();
                PCollection<String> results = c.pipeline()
                    .apply(ElasticsearchIO.read()
                        .withConnectionConfiguration(
                            ElasticsearchIO.ConnectionConfiguration.create(hosts, indexName))
                        .withQuery(query));
                c.output(results);
            }
        })
    .apply(Flatten.pCollections()));

In general I'm wondering for any of IO-related classes proved by Beam that conforms to PBegin input -- if there is a means to introduce a collection. Here is one approach that might be promising:

// Define a ValueProvider for a List<String>
ValueProvider<List<String>> myListProvider = ValueProvider.StaticValueProvider.of(myList);

// Use the ValueProvider to create a PCollection of Strings
PCollection<String> pcoll = pipeline.apply(Create.ofProvider(myListProvider, ListCoder.of()));

Upvotes: 0

Views: 140

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