Read API throws NPE for empty tables

[o-shevchenko]

We get NPE when we read an empty table using Read API.
NPE happens here:

java-bigquery/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/BigQueryResultImpl.java

Line 120 in 4061922

cursor = buffer.take(); // advance the cursor,Potentially blocking operation

When we run query Using Fast Query Path (Read API disabled) such code works fine.buffer.take() returns cursor and it correctly indicated in isEndOfStream as EndOfFieldValueList.
But when we enable Read API buffer.take() throws NPE since buffer is null.

Environment details

com.google.cloud:google-cloud-bigquery:2.45.0
Mac OS Sonoma M1
Java version: 17

Steps to reproduce

1. Enable Read API (make sure you see Not Using Fast Query Path, using jobs.insert, see related issue I've attached)
2. Read the empty table
3. Execute next()

Code example

val connectionSettings = ConnectionSettings.newBuilder()
                    .setJobTimeoutMs(Long.MAX_VALUE) // that is crucial to enable Read API, see the attached issue
                    .setRequestTimeout(DEFAULT_QUERY_TIMEOUT_MS)
                    .setUseReadAPI(true)
                    .setMaxResults(DEFAULT_MAX_RESULT)
                    .setUseQueryCache(true)
                    .build()
                val connection = context.createConnection(connectionSettings)
                val bqResult = connection.executeSelect(code)
                bqResult.resultSet.next() // NPE
                

Stack trace

 onError(java.lang.NullPointerException: Cannot invoke "java.util.concurrent.BlockingQueue.take()" because the return value of "com.google.cloud.bigquery.BigQueryResultImpl.access$200(com.google.cloud.bigquery.BigQueryResultImpl)" is null))
 at com.google.cloud.bigquery.BigQueryResultImpl$BigQueryResultSet.next(BigQueryResultImpl.java:120)

Related issue: googleapis/java-bigquerystorage#2764
#3624

[PhongChuong]

Thanks for the concise bug report.
I'll send a PR for a fix.

[PhongChuong]

The fix should roll out in the next release. Thanks for the bug report.