gsmiller commented on code in PR #12560:
URL: https://github.com/apache/lucene/pull/12560#discussion_r1327725540
##########
lucene/expressions/src/java/org/apache/lucene/expressions/ExpressionFunctionValues.java:
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@@ -39,21 +39,21 @@ class ExpressionFunctionValues extends DoubleValues {
}
@Override
- public boolean advanceExact(int doc) {
+ public boolean advanceExact(int doc) throws IOException {
if (currentDoc == doc) {
return true;
}
+ for (DoubleValues v : functionValues) {
+ v.advanceExact(doc);
Review Comment:
If you have an expression like `a == 0 ? b : c` where `a`, `b` and `c` are
all other references in your bindings, only `b` or `c` need to be evaluated for
any given doc, not both. But today, we greedily call `advanceExact` on all
three up-front, for every doc. So we're doing wasted advancing work for one of
`b` or `c` for every single doc. I added a similar example in a test case.
Depending on what the advancing is doing, this could come with significant
cost (e.g., if `b` or `c` is another complex expression tree that ends up
propagating the advance down all of its dependencies)
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