romseygeek commented on code in PR #15083:
URL: https://github.com/apache/lucene/pull/15083#discussion_r2282720998
##########
lucene/core/src/java/org/apache/lucene/index/DocValuesSkipper.java:
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@@ -122,4 +123,61 @@ public final void advance(long minValue, long maxValue)
throws IOException {
advance(maxDocID + 1);
}
}
+
+ /**
+ * Returns the minimum value for a field across all segments, or {@link
Long#MIN_VALUE} if not
+ * available
+ *
+ * @param searcher a searcher over the index
+ * @param field the field to retrieve values for
+ */
+ public static long globalMinValue(IndexSearcher searcher, String field)
throws IOException {
+ long minValue = Long.MAX_VALUE;
+ for (LeafReaderContext ctx : searcher.getLeafContexts()) {
+ DocValuesSkipper skipper = ctx.reader().getDocValuesSkipper(field);
+ if (skipper == null) {
+ minValue = Long.MIN_VALUE;
+ } else {
+ minValue = Math.min(minValue, skipper.minValue());
+ }
+ }
+ return minValue;
+ }
+
+ /**
+ * Returns the maximum value for a field across all segments, or {@link
Long#MIN_VALUE} if not
+ * available
+ *
+ * @param searcher a searcher over the index
+ * @param field the field to retrieve values for
+ */
+ public static long globalMaxValue(IndexSearcher searcher, String field)
throws IOException {
+ long maxValue = Long.MIN_VALUE;
+ for (LeafReaderContext ctx : searcher.getLeafContexts()) {
+ DocValuesSkipper skipper = ctx.reader().getDocValuesSkipper(field);
+ if (skipper == null) {
+ maxValue = Long.MAX_VALUE;
+ } else {
+ maxValue = Math.max(maxValue, skipper.maxValue());
+ }
+ }
+ return maxValue;
+ }
+
+ /**
+ * Returns the total skipper document count for a field across all segments
+ *
+ * @param searcher a searcher over the index
+ * @param field the field to retrieve values for
+ */
+ public static int globalDocCount(IndexSearcher searcher, String field)
throws IOException {
+ int docCount = 0;
+ for (LeafReaderContext ctx : searcher.getLeafContexts()) {
+ DocValuesSkipper skipper = ctx.reader().getDocValuesSkipper(field);
+ if (skipper != null) {
+ docCount += skipper.docCount();
+ }
+ }
+ return docCount;
+ }
Review Comment:
In general I'd expect this to be used to check that all documents in a
reader are included in the skipper (ie, there aren't any documents with no
value in this field). If you have a MultiReader which includes segments with
skippers and segments without, then this will return a value that is less that
the top-level reader's `maxDoc()`, so you would know not to use the global
values as a shortcut for an all-values-match check.
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