Hi @goccy,

We use the BigQuery JDBC driver (see documentation) in our project and would like to add integration tests using bigquery-emulator.

It's possible to specify a custom endpoint for the driver using the undocumented RootURL argument, e.g.:

jdbc:bigquery://http://localhost/:9050;RootURL=http://localhost:9050;ProjectId=test;OAuthType=2;OAuthAccessToken=<token>

During our tests we found the following issues caused by the JDBC driver's behavior. We would like to contribute to your project and fix these issues if that's ok for you.

Path prefix

The driver always uses path prefix /bigquery/v2, e.g. POST /bigquery/v2/projects/test/queries. This is not configurable.
We propose to add a command line switch that allows overriding the default prefix "", e.g.:

--path-prefix="/bigquery/v2"

Content-Encoding gzip

The driver sends payload with Content-Encoding: gzip. This is not configurable.
We propose to add a middleware function to server.go that unzips the request payload if necessary.
This would require adding an additional dependency, e.g. github.com/klauspost/compress/gzip.

Job ID

When sending a SQL query, the JDBC driver sends request POST /bigquery/v2/projects/test/queries with the following payload:

{"dryRun":false,"maxResults":10000,"query":"select 2*5","timeoutMs":10000,"useLegacySql":false,"useQueryCache":true}

The emulator replies with this response:

{"jobComplete":true,"jobReference":{"projectId":"test"},"rows":[{"f":[{"v":"10"}]}],"schema":{"fields":[{"name":"$col1","type":"INTEGER"}]},"totalRows":"1"}

This causes the following exception in the JDBC driver which is caused by the missing jobId in jobReference.

java.sql.SQLException: [Simba][BigQueryJDBCDriver](100030) Error trying to obtain Google Bigquery object.
	at com.simba.googlebigquery.googlebigquery.dataengine.BQResultSet.<init>(Unknown Source)
	at com.simba.googlebigquery.googlebigquery.dataengine.BQSQLExecutor.execute(Unknown Source)
	at com.simba.googlebigquery.jdbc.common.SStatement.executeNoParams(Unknown Source)
	at com.simba.googlebigquery.jdbc.common.BaseStatement.executeQuery(Unknown Source)
	at com.exasol.adapter.dialects.bigquery.BigQueryJdbcTest.test(BigQueryJdbcTest.java:23)

The emulator uses r.queryRequest.RequestId as jobId (see handler.go) which is nil in this case.

We propose to generate a random ID in case r.queryRequest.RequestId is nil.

If these changes are OK for you, we would like create separate pull requests for each of these issues, or discuss how to solve them in a different way.

Thank you very much for your support!