/**
* Infers predicates for a project.
*
* <ol>
* <li>create a mapping from input to projection. Map only positions that directly reference an
* input column.
* <li>Expressions that only contain above columns are retained in the Project's pullExpressions
* list.
* <li>For e.g. expression 'a + e = 9' below will not be pulled up because 'e' is not in the
* projection list.
* <pre>
* childPullUpExprs: {a > 7, b + c < 10, a + e = 9}
* projectionExprs: {a, b, c, e / 2}
* projectionPullupExprs: {a > 7, b + c < 10}
* </pre>
* </ol>
*/
public RelOptPredicateList getPredicates(Project project) {
RelNode child = project.getInput();
final RexBuilder rexBuilder = project.getCluster().getRexBuilder();
RelOptPredicateList childInfo = RelMetadataQuery.getPulledUpPredicates(child);
List<RexNode> projectPullUpPredicates = new ArrayList<RexNode>();
ImmutableBitSet.Builder columnsMappedBuilder = ImmutableBitSet.builder();
Mapping m =
Mappings.create(
MappingType.PARTIAL_FUNCTION,
child.getRowType().getFieldCount(),
project.getRowType().getFieldCount());
for (Ord<RexNode> o : Ord.zip(project.getProjects())) {
if (o.e instanceof RexInputRef) {
int sIdx = ((RexInputRef) o.e).getIndex();
m.set(sIdx, o.i);
columnsMappedBuilder.set(sIdx);
}
}
// Go over childPullUpPredicates. If a predicate only contains columns in
// 'columnsMapped' construct a new predicate based on mapping.
final ImmutableBitSet columnsMapped = columnsMappedBuilder.build();
for (RexNode r : childInfo.pulledUpPredicates) {
ImmutableBitSet rCols = RelOptUtil.InputFinder.bits(r);
if (columnsMapped.contains(rCols)) {
r = r.accept(new RexPermuteInputsShuttle(m, child));
projectPullUpPredicates.add(r);
}
}
// Project can also generate constants. We need to include them.
for (Ord<RexNode> expr : Ord.zip(project.getProjects())) {
if (RexLiteral.isNullLiteral(expr.e)) {
projectPullUpPredicates.add(
rexBuilder.makeCall(
SqlStdOperatorTable.IS_NULL, rexBuilder.makeInputRef(project, expr.i)));
} else if (RexUtil.isConstant(expr.e)) {
final List<RexNode> args =
ImmutableList.of(rexBuilder.makeInputRef(project, expr.i), expr.e);
final SqlOperator op =
args.get(0).getType().isNullable() || args.get(1).getType().isNullable()
? SqlStdOperatorTable.IS_NOT_DISTINCT_FROM
: SqlStdOperatorTable.EQUALS;
projectPullUpPredicates.add(rexBuilder.makeCall(op, args));
}
}
return RelOptPredicateList.of(projectPullUpPredicates);
}
