private boolean hasEqualityConstraints(int startPos, int endPos) {
ScanRanges ranges = context.getScanRanges();
// If a GROUP BY is being done, then the rows are ordered according to the GROUP BY key,
// not by the original row key order of the table (see PHOENIX-3451).
// We check each GROUP BY expression to see if it only references columns that are
// matched by equality constraints, in which case the expression itself would be constant.
// FIXME: this only recognizes row key columns that are held constant, not all columns.
// FIXME: we should optimize out any GROUP BY or ORDER BY expression which is deemed to
// be held constant based on the WHERE clause.
if (!groupBy.isEmpty()) {
for (int pos = startPos; pos < endPos; pos++) {
IsConstantVisitor visitor = new IsConstantVisitor(this.projector, ranges);
List<Expression> groupByExpressions = groupBy.getExpressions();
if (pos >= groupByExpressions.size()) { // sanity check - shouldn't be necessary
return false;
}
Expression groupByExpression = groupByExpressions.get(pos);
if (groupByExpression.getDeterminism().ordinal() > Determinism.PER_STATEMENT.ordinal()) {
return false;
}
Boolean isConstant = groupByExpression.accept(visitor);
if (!Boolean.TRUE.equals(isConstant)) {
return false;
}
}
return true;
}
for (int pos = startPos; pos < endPos; pos++) {
if (!ranges.hasEqualityConstraint(pos)) {
return false;
}
}
return true;
}
@Override
public Boolean defaultReturn(Expression node, List<Boolean> returnValues) {
if (node.getDeterminism().ordinal() > Determinism.PER_STATEMENT.ordinal()
|| returnValues.size() < node.getChildren().size()) {
return Boolean.FALSE;
}
for (Boolean returnValue : returnValues) {
if (!returnValue) {
return Boolean.FALSE;
}
}
return Boolean.TRUE;
}