...
outPreds = qci.getOnOutputPredicates();
...
for (OnOutputPredicate outPred : outPreds)
{
boolean pushedToFunction = false;
List<ColumnDefinition> predOutCols = outPred.getColumns();
...
// The following is an example of predicate push-down to input,
// where input column names are different
// from output column names.
// Semantically, the md5sum column doesn't have an input counter-part,
// so the predicate on that column cannot be pushed down.
// Thus, some predicates can be pushed down to input, and some cannot
// depending on which columns are involved in the predicate.
// This is specified in the completePlanningContract method
//
if (!pushedToFunction)
{
// The helper function returns a 1-to-1 mapping of the output
// columns mapped to their input counterparts.
// If no such mapping can be made (for instance, if the
// output column corresponds to an md5sum for which there is no
// corresponding input), the helper function returns null
List<ColumnDefinition> mappedCols
= mapOutputColumnsToInput (predOutCols);
if (mappedCols != null)
{
OnInputPredicate onInputPredicate = outPred.pushToInput(mappedCols);
onInputPredicates.add(onInputPredicate);
}
}
} // for each outPred
...
InputContext inputContext = new InputContext.Builder()
...
.setOnInputPredicates(onInputPredicates)
.toInputContext();
...
For full context, see Examples.