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https://issues.apache.org/jira/browse/CALCITE-4964?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17466649#comment-17466649
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Jacques Nadeau commented on CALCITE-4964:
-----------------------------------------
An additional note here: if we do adjust code for optimization reasons, I'd
prefer for us to get into the habit of also implementing microbenchmarks for
the code. Otherwise, future changes are likely to regress things. It also
establishes a clear ask for future changes in this code where we can ask a
contributor to report the benchmark impact before accepting additional changes.
> Reduce recursion when push predicate into CASE
> ----------------------------------------------
>
> Key: CALCITE-4964
> URL: https://issues.apache.org/jira/browse/CALCITE-4964
> Project: Calcite
> Issue Type: Improvement
> Reporter: Ziwei Liu
> Assignee: Ziwei Liu
> Priority: Major
>
> I think CaseShuttle do not need a loop of for(;; ).When a predicate is pushed
> into case, we only need to check the new RexCall whether need to push
> predicate into the child operand, not need to do a new recursion.
> So I think CaseShuttle can be reduced like:
> {code:java}
> @Override public RexNode visitCall(RexCall call) {
> call = (RexCall) super.visitCall(call);
> if (call instanceof OdpsLambdaRexCall) {
> return call;
> }
> final RexCall old = call;
> call = ReduceExpressionsRule.pushPredicateIntoCase(call);
> if (call == old) {
> return call;
> } else {
> boolean containCase = false;
> List<RexNode> newOps = new ArrayList<>(call.getOperands().size());
> // call will be like case when c1 then f(x1 ...)
> // check whether need push f into x1
> for (int i = 0; i < call.getOperands().size(); i ++) {
> RexNode op = call.getOperands().get(i);
> RexNode newOp = op;
> if (i % 2 == 1 || i == call.getOperands().size() - 1) {
> if (op instanceof RexCall) {
> newOp = ReduceExpressionsRule.pushPredicateIntoCase((RexCall)
> op);
> }
> }
> if (op != newOp) {
> containCase = true;
> }
> newOps.add(newOp);
> }
> if (!containCase) {
> return call;
> } else {
> return call.clone(call.getType(), newOps);
> }
> }
> } {code}
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