[BEAM-9267] A BeamSQL UDF that returns a Map fails always with NullPointerException.

• Type: Bug
• Status: Resolved
• Priority: P3
• Resolution: Fixed
• Affects Version/s: 2.19.0
• Fix Version/s: Missing
• Component/s: dsl-sql
• Assignee: Niels Basjes
• Reporter: Niels Basjes
• Created: 07/Feb/20 12:29
• Updated: 13/Jan/22 21:52
• Resolved: 08/Sep/21 13:18

Description

When I create a UDF that returns a Map<String, String> and call it from within a SQL statement it consistently fails with a NullPointerException

My UDF

public class FooMap implements SerializableFunction<String, Map<String, String>> {
    @Override
    public Map<String, String> apply(String input) {
        final HashMap<String, String> hashMap = new HashMap<>();
        hashMap.put("Some", "Thing");
        return hashMap;
    }
}

and

public class BarString implements SerializableFunction<String, String> {
    @Override
    public String apply(String input) {
        return new StringBuilder(input).reverse().toString();
    }
}

My test

@Category(ValidatesRunner.class)
public class TestFunctionReturnsMap implements Serializable {

    private static final Logger LOG = LoggerFactory.getLogger(TestFunctionReturnsMap.class);

    @Rule
    public final transient TestPipeline pipeline = TestPipeline.create();

    @Test
    @Category(NeedsRunner.class)
    public void testUserAgentAnalysisSQL() {

        // ============================================================
        // Create input PCollection<Row>
        Schema inputSchema = Schema
            .builder()
            .addStringField("bar")
            .build();

        PCollection<Row> input = pipeline
            .apply(Create.of(Arrays.asList("One", "Two", "Three")))
            .setCoder(StringUtf8Coder.of())
            .apply(ParDo.of(new DoFn<String, Row>() {
                @ProcessElement
                public void processElement(ProcessContext c) {
                    c.output(Row
                        .withSchema(inputSchema)
                        .addValues(c.element())
                        .build());
                }
            })).setRowSchema(inputSchema);


        // ============================================================

        PCollection<Row> result =
            // This way we give a name to the input stream for use in the SQL
            PCollectionTuple.of("InputStream", input)
                // Apply the SQL with the UDFs we need.
                .apply("Execute SQL", SqlTransform
                    .query(
                        "SELECT" +
                        "   bar             AS bar" +
                        "  ,Bar(bar)        AS barbar " +
                        "  ,Foo(bar)        AS foobar " +
                        "FROM InputStream")
                    .registerUdf("Foo",     new FooMap())
                    .registerUdf("Bar",     new BarString())
                );

        result.apply(ParDo.of(new RowPrinter()));

        pipeline.run().waitUntilFinish();
    }

    public static class RowPrinter extends DoFn<Row, Row> {
        @ProcessElement
        public void processElement(ProcessContext c) {
            final Row row = c.element();
            LOG.info("ROW: {} --> {}", row, row.getSchema());
        }
    }
}

The Exception I always get

java.lang.NullPointerException: Null type

	at org.apache.beam.sdk.schemas.AutoValue_Schema_Field$Builder.setType(AutoValue_Schema_Field.java:84)
	at org.apache.beam.sdk.schemas.Schema$Field.of(Schema.java:893)
	at org.apache.beam.sdk.extensions.sql.impl.utils.CalciteUtils.toField(CalciteUtils.java:234)
	at org.apache.beam.sdk.extensions.sql.impl.utils.CalciteUtils.toField(CalciteUtils.java:230)
	at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
	at java.util.Iterator.forEachRemaining(Iterator.java:116)
	at java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801)
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:482)
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:472)
	at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:566)
	at org.apache.beam.sdk.extensions.sql.impl.utils.CalciteUtils.toSchema(CalciteUtils.java:189)
	at org.apache.beam.sdk.extensions.sql.impl.rel.BeamCalcRel$Transform.expand(BeamCalcRel.java:129)
	at org.apache.beam.sdk.extensions.sql.impl.rel.BeamCalcRel$Transform.expand(BeamCalcRel.java:110)
	at org.apache.beam.sdk.Pipeline.applyInternal(Pipeline.java:539)
	at org.apache.beam.sdk.Pipeline.applyTransform(Pipeline.java:490)
	at org.apache.beam.sdk.extensions.sql.impl.rel.BeamSqlRelUtils.toPCollection(BeamSqlRelUtils.java:69)
	at org.apache.beam.sdk.extensions.sql.impl.rel.BeamSqlRelUtils.toPCollection(BeamSqlRelUtils.java:39)
	at org.apache.beam.sdk.extensions.sql.SqlTransform.expand(SqlTransform.java:125)
	at org.apache.beam.sdk.extensions.sql.SqlTransform.expand(SqlTransform.java:83)
	at org.apache.beam.sdk.Pipeline.applyInternal(Pipeline.java:539)
	at org.apache.beam.sdk.Pipeline.applyTransform(Pipeline.java:490)
	at org.apache.beam.sdk.values.PCollectionTuple.apply(PCollectionTuple.java:261)
	at nl.basjes.parse.useragent.beam.TestFunctionReturnsMap.testUserAgentAnalysisSQL(TestFunctionReturnsMap.java:81)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)

 

Issue Links

• is blocked by: BEAM-9379 Upgrade to Calcite 1.26.0