select * from (
	select
		test_a.a
	from pg.test_a
	group by
		test_a.a
	union all
	select
		1 as a
) as x
where a = 1;

01:07:04,815 WARN  [org.teiid.CONNECTOR] (Worker12_QueryProcessorQueue114) enPDJlWH1O/y Connector worker process failed for atomic-request=enPDJlWH1O/y.34.5.30: org.teiid.translator.jdbc.JDBCExecutionException: 0 TEIID11008:TEIID11004 Error executing statement(s): [Prepared Values: [] SQL: SELECT g_0."a" FROM "public"."test_a" AS g_0 WHERE anon_grp0.gcol0 = 1 GROUP BY g_0."a"]
        at org.teiid.translator.jdbc.JDBCQueryExecution.execute(JDBCQueryExecution.java:131)
        at org.teiid.dqp.internal.datamgr.ConnectorWorkItem.execute(ConnectorWorkItem.java:365)
        at sun.reflect.GeneratedMethodAccessor93.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:606)
        at org.teiid.dqp.internal.datamgr.ConnectorManager$1.invoke(ConnectorManager.java:211)
        at com.sun.proxy.$Proxy29.execute(Unknown Source)
        at org.teiid.dqp.internal.process.DataTierTupleSource.getResults(DataTierTupleSource.java:306)
        at org.teiid.dqp.internal.process.DataTierTupleSource$1.call(DataTierTupleSource.java:112)
        at org.teiid.dqp.internal.process.DataTierTupleSource$1.call(DataTierTupleSource.java:108)
        at java.util.concurrent.FutureTask.run(FutureTask.java:262)
        at org.teiid.dqp.internal.process.FutureWork.run(FutureWork.java:65)
        at org.teiid.dqp.internal.process.DQPWorkContext.runInContext(DQPWorkContext.java:276)
        at org.teiid.dqp.internal.process.ThreadReuseExecutor$RunnableWrapper.run(ThreadReuseExecutor.java:119)
        at org.teiid.dqp.internal.process.ThreadReuseExecutor$3.run(ThreadReuseExecutor.java:210)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at java.lang.Thread.run(Thread.java:745)
Caused by: org.postgresql.util.PSQLException: PSQLException-ERROR: missing FROM-clause entry for table "anon_grp0"
  Position: 52
        at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2157)
        at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1886)
        at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:255)
        at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:555)
        at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:417)
        at org.postgresql.jdbc2.AbstractJdbc2Statement.executeQuery(AbstractJdbc2Statement.java:302)
        at org.jboss.jca.adapters.jdbc.WrappedPreparedStatement.executeQuery(WrappedPreparedStatement.java:504)
        at org.teiid.translator.jdbc.JDBCQueryExecution.execute(JDBCQueryExecution.java:123)
        ... 17 more

01:07:05,004 WARN  [org.teiid.PROCESSOR] (Worker11_QueryProcessorQueue116) enPDJlWH1O/y TEIID30020 Processing exception for request enPDJlWH1O/y.34 'TEIID30504 test_tables_pg: 0 TEIID11008:TEIID11004 Error executing statement(s): [Prepared Values: [] SQL: SELECT g_0."a" FROM "public"."test_a" AS g_0 WHERE anon_grp0.gcol0 = 1 GROUP BY g_0."a"]'. Originally TeiidProcessingException 'PSQLException-ERROR: missing FROM-clause entry for table "anon_grp0"
  Position: 52' QueryExecutorImpl.java:2157. Enable more detailed logging to see the entire stacktrace.