// do the same on the build side
LocalExecutionPlanContext buildContext = context.createSubContext();
PhysicalOperation buildSource = buildNode.accept(this, buildContext);
List<Integer> buildChannels = ImmutableList.copyOf(getChannelsForSymbols(buildSymbols, buildSource.getLayout()));
HashBuilderOperatorFactory hashBuilderOperatorFactory = new HashBuilderOperatorFactory(
buildContext.getNextOperatorId(),
buildSource.getTypes(),
buildChannels,
100_000);
LookupSourceSupplier lookupSourceSupplier = hashBuilderOperatorFactory.getLookupSourceSupplier();
DriverFactory buildDriverFactory = new DriverFactory(
buildContext.isInputDriver(),
false,
ImmutableList.<OperatorFactory>builder()
.addAll(buildSource.getOperatorFactories())