Processing Presto ResultSet in Java: 'SQLException: Not on a valid row' - docker

Question

My Presto plugin has two components:
An EventListener that logs stats of queries made to Presto
Some UDFs for hashing (MD5, SHA1) common datatypes (varchar, long) and returning result as varchar
I've already done:
Integration-test (mvn verify) of query-logging component
Unit-test of hashing UDFs
In integration test of UDF component, I'm tyring to assert value returned by my UDF by firing a query
Connection connection = DriverManager.getConnection(PRESTO_URL, PRESTO_USER, PRESTO_PASSWORD);
Statement statement = connection.createStatement();
ResultSet resultSet = statement.executeQuery("SELECT SHA1(9223372036854775807) AS hash");
assertEquals("458B642B137E2C76E0B746C6FA43E64C3D4C47F1", resultSet.getString("hash"));
This gives following stack-trace (PrestoResultSet.checkValidRow)
NOTE: ExtendedHashFunctionsTestIT.java:39 line is the one containing resultSet.getString(..)
java.sql.SQLException: Not on a valid row
at com.facebook.presto.jdbc.PrestoResultSet.checkValidRow(PrestoResultSet.java:1658)
at com.facebook.presto.jdbc.PrestoResultSet.column(PrestoResultSet.java:1690)
at com.facebook.presto.jdbc.PrestoResultSet.getString(PrestoResultSet.java:370)
at com.company.plugin.it.udfs.scalar.hash.ExtendedHashFunctionsTestIT.testBody(ExtendedHashFunctionsTestIT.java:39)
at com.company.plugin.it.AbstractIntegrationTest.test(AbstractIntegrationTest.java:77)
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.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:85)
at org.testng.internal.Invoker.invokeMethod(Invoker.java:639)
at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:816)
at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1124)
at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:125)
at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:108)
at org.testng.TestRunner.privateRun(TestRunner.java:774)
at org.testng.TestRunner.run(TestRunner.java:624)
at org.testng.SuiteRunner.runTest(SuiteRunner.java:359)
at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:354)
at org.testng.SuiteRunner.privateRun(SuiteRunner.java:312)
at org.testng.SuiteRunner.run(SuiteRunner.java:261)
at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:86)
at org.testng.TestNG.runSuitesSequentially(TestNG.java:1191)
at org.testng.TestNG.runSuitesLocally(TestNG.java:1116)
at org.testng.TestNG.run(TestNG.java:1024)
at org.apache.maven.surefire.testng.TestNGExecutor.run(TestNGExecutor.java:62)
at org.apache.maven.surefire.testng.TestNGDirectoryTestSuite.execute(TestNGDirectoryTestSuite.java:141)
at org.apache.maven.surefire.Surefire.run(Surefire.java:180)
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.apache.maven.surefire.booter.SurefireBooter.runSuitesInProcess(SurefireBooter.java:350)
at org.apache.maven.surefire.booter.SurefireBooter.main(SurefireBooter.java:1021)
I'm perplexed because error occurs only when I try to access ResultSet; commenting out the assertEquals(..) statement lets the test run successfully.
What's even more disturbing is that stack-trace is same for virtually any query:
SELECT 'some_string' AS some_alias
SHOW SCHEMAS
I'm using Spotify's dockerfile-maven-plugin for the tests. I've put up relevant files in this GitHub Gist
ExtendedHashFunctionsTestIT.java (simplified integration-test file)
pom.xml
Dockerfile

Answer 1

It laments me to think that the mistake that ate up my 2 days was this
Connection connection = DriverManager.getConnection(PRESTO_URL, PRESTO_USER, PRESTO_PASSWORD);
Statement statement = connection.createStatement();
ResultSet resultSet = statement.executeQuery("SELECT SHA1(9223372036854775807) AS hash");
resultSet.next();
assertEquals("458B642B137E2C76E0B746C6FA43E64C3D4C47F1", resultSet.getString("hash"));
That 4th line: I had missed resultSet.next() prior to resultSet.getString(..) :-(