Check if merge is aborted before executing file integrity checks (#16264)

Adds OneMerge to the MergeState so that merge writers and consumers 
can check the abort flag before starting each reader's checkIntegrity(). 
This avoids kicking off costly full-file checksums on segments when the 
merge has already been aborted.

Author: tlrx

lucene/CHANGES.txt

@@ -410,6 +410,9 @@ Improvements
   DiversifiedTopDocsCollector, removing usages of the deprecated IndexSearcher#search(Query, Collector).
   (Luca Cavanna)
 
+* GITHUB#16264: Check if merge is aborted before executing file integrity checks to avoid
+  costly full-file checksums on segments when the merge has already been cancelled. (Tanguy Leroux)
+
 Optimizations
 ---------------------
 * GITHUB#16111: Optimize FieldExistsQuery.count() when all docs have the field. (Prithvi S)

lucene/core/src/java/org/apache/lucene/codecs/DocValuesConsumer.java

@@ -132,6 +132,7 @@ public abstract void addSortedSetField(FieldInfo field, DocValuesProducer values
   public void merge(MergeState mergeState) throws IOException {
     for (DocValuesProducer docValuesProducer : mergeState.docValuesProducers) {
       if (docValuesProducer != null) {
+        mergeState.checkAborted();
         docValuesProducer.checkIntegrity();
       }
     }

lucene/core/src/java/org/apache/lucene/codecs/FieldsConsumer.java

@@ -80,6 +80,7 @@ public void merge(MergeState mergeState, NormsProducer norms) throws IOException
 
       final int maxDoc = mergeState.maxDocs[readerIndex];
       if (f != null) {
+        mergeState.checkAborted();
         f.checkIntegrity();
         slices.add(new ReaderSlice(docBase, maxDoc, readerIndex));
         fields.add(f);

lucene/core/src/java/org/apache/lucene/codecs/KnnVectorsWriter.java

@@ -113,6 +113,7 @@ public final void merge(MergeState mergeState) throws IOException {
       KnnVectorsReader reader = mergeState.knnVectorsReaders[i];
       assert reader != null || mergeState.fieldInfos[i].hasVectorValues() == false;
       if (reader != null) {
+        mergeState.checkAborted();
         reader.checkIntegrity();
       }
     }

lucene/core/src/java/org/apache/lucene/codecs/NormsConsumer.java

@@ -66,6 +66,7 @@ public abstract void addNormsField(FieldInfo field, NormsProducer normsProducer)
   public void merge(MergeState mergeState) throws IOException {
     for (NormsProducer normsProducer : mergeState.normsProducers) {
       if (normsProducer != null) {
+        mergeState.checkAborted();
         normsProducer.checkIntegrity();
       }
     }

lucene/core/src/java/org/apache/lucene/codecs/PointsWriter.java

@@ -222,6 +222,7 @@ public void merge(MergeState mergeState) throws IOException {
     // check each incoming reader
     for (PointsReader reader : mergeState.pointsReaders) {
       if (reader != null) {
+        mergeState.checkAborted();
         reader.checkIntegrity();
       }
     }

lucene/core/src/java/org/apache/lucene/codecs/StoredFieldsWriter.java

@@ -130,6 +130,7 @@ public int merge(MergeState mergeState) throws IOException {
     List<StoredFieldsMergeSub> subs = new ArrayList<>();
     for (int i = 0; i < mergeState.storedFieldsReaders.length; i++) {
       StoredFieldsReader storedFieldsReader = mergeState.storedFieldsReaders[i];
+      mergeState.checkAborted();
       storedFieldsReader.checkIntegrity();
       subs.add(
           new StoredFieldsMergeSub(

lucene/core/src/java/org/apache/lucene/codecs/TermVectorsWriter.java

@@ -200,6 +200,7 @@ public int merge(MergeState mergeState) throws IOException {
     for (int i = 0; i < mergeState.termVectorsReaders.length; i++) {
       TermVectorsReader reader = mergeState.termVectorsReaders[i];
       if (reader != null) {
+        mergeState.checkAborted();
         reader.checkIntegrity();
       }
       subs.add(new TermVectorsMergeSub(mergeState.docMaps[i], reader, mergeState.maxDocs[i]));

lucene/core/src/java/org/apache/lucene/codecs/lucene90/Lucene90PointsWriter.java

@@ -204,6 +204,7 @@ public void merge(MergeState mergeState) throws IOException {
     }
     for (PointsReader reader : mergeState.pointsReaders) {
       if (reader != null) {
+        mergeState.checkAborted();
         reader.checkIntegrity();
       }
     }

lucene/core/src/java/org/apache/lucene/codecs/lucene90/compressing/Lucene90CompressingStoredFieldsWriter.java

@@ -601,6 +601,7 @@ public int merge(MergeState mergeState) throws IOException {
         new ArrayList<>(mergeState.storedFieldsReaders.length);
     for (int i = 0; i < mergeState.storedFieldsReaders.length; i++) {
       final StoredFieldsReader reader = mergeState.storedFieldsReaders[i];
+      mergeState.checkAborted();
       reader.checkIntegrity();
       MergeStrategy mergeStrategy = getMergeStrategy(mergeState, matchingReaders, i);
       if (mergeStrategy == MergeStrategy.VISITOR) {