mayya-sharipova commented on a change in pull request #204:
URL: https://github.com/apache/lucene/pull/204#discussion_r664573881
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File path:
lucene/core/src/java/org/apache/lucene/search/comparators/DocComparator.java
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@@ -81,7 +87,12 @@ public Integer value(int slot) {
public DocLeafComparator(LeafReaderContext context) {
this.docBase = context.docBase;
if (enableSkipping) {
- this.minDoc = topValue + 1;
+ // For a single sort on _doc, we want to skip all docs before topValue.
+ // For multiple fields sort on [_doc, other fields], we want to
include docs with the same
+ // docID.
+ // This is needed in a distributed search, where there are docs from
different indices with
+ // the same docID.
+ this.minDoc = singleSort ? topValue + 1 : topValue;
Review comment:
Great comment! +1 for simplifying the code at the expense for extra
single case in `DocComparator`.
For `NumericComparator` though this is not the case, and there could be huge
number of docs with the same value, so extra optimization for `singleSort` is
important.
> I guess it doesn't specifically address the case where _doc is the last
sort, for example a sort on ["some_field", "_doc"], where we could also use
topValue + 1.
No, the sort optimizations in `DocComparator` are not applicable where
`_doc` is the 1st sort.
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