Digest is suitable for telling whether two expressions (RexNodes) are
equivalent. And it makes a good key for hash-maps.
However if I may rule was looking for a particular pattern I wouldn't match
on digest. Instead of
RexNode rex;
if (!rex.getDigest().equalTo("+($0, 1)") {
return;
}
I would write
RexNode rex;
switch (rex.getKind()) {
default:
return; // not a match
case PLUS:
switch (rex.getOperands().get(0).getKind()) {
default:
return; // not a match
case LITERAL:
RexLiteral literal = (RexLiteral) rex.getOperands().get(0);
if (!1.equals(literal.getValue()) {
return; // not a match
}
// fall through; we got a match
}
}
(I'm using RexNode.getKind() here because it works for the common node
types. You can also use 'rex instanceof ...' and '((RexCall)
rex).getOperator() == SqlStdOperatorTable.MY_OPERATOR'.)
Julian
On Wed, Aug 13, 2014 at 6:54 AM, Ravi Nallappan <[email protected]>
wrote:
> Hi,
>
> Within onMatch() for ProjectRel, is it intended to use digest string (via
> toString) to lookup content of RexNode tree or its advisable to traverse
> through the nodes instead for the purpose?
>
> if (n instanceof RexCall && n.toString().compareTo("+(4, 2)") == 0) {...}
>
> Thanks & Regards,
> Ravi Nallappan
>
