This repository was archived by the owner on Feb 24, 2026. It is now read-only.
This repository was archived by the owner on Feb 24, 2026. It is now read-only.
Reading data using the executeSelect API is slow #2764
Description
We use executeSelect API to run SQL query and read results from BigQuery. We expected a good speed based on this article
Reading data using executeSelectAPI is extremely slow.
Reading of 100_000 rows takes 23930 ms.
The profiling showed no prominent places where we spent most of the time.
Are there any recent changes that might cause performance degradation for such an API?
Do you have a benchmark to understand what performance we should expect?
Thanks!
Environment details
com.google.cloud:google-cloud-bigquery:2.43.3- Mac OS Sonoma M1
- Java version: 17
Code example
Mono.fromCallable { bigQueryOptionsBuilder.build().service }
.flatMap { context ->
val connectionSettings = ConnectionSettings.newBuilder()
.setRequestTimeout(10L)
.setUseReadAPI(true)
.setMaxResults(1000)
.setNumBufferedRows(1000)
.setUseQueryCache(true)
.build();
val connection = context.createConnection(connectionSettings)
val bqResult = connection.executeSelect(sql)
val result = Flux.usingWhen(
Mono.just(bqResult.resultSet),
{ resultSet -> resultSet.toFlux(bqResult.schema) },
{ _ -> Mono.fromRunnable<Unit> { connection.close() } }
)
Mono.just(Data(result, bqResult.schema.toSchema()))
}
...
fun ResultSet.toFlux(schema:Schema): Flux<DataRecord> {
return Flux.generate<DataRecord> { sink ->
if (next()) {
sink.next(toDataRecord(schema))
} else {
sink.complete()
}
}
}