Allow reading vectors where dim is in the file (#130138)

This allows configuration to have a `-1` dim to read files that have the
`dim` in the file.

Additionally, allows setting numQuerys to `0` to skip the search phase
easily.

qa/vector/src/main/java/org/elasticsearch/test/knn/CmdLineArgs.java

@@ -262,8 +262,10 @@ record CmdLineArgs(
             if (docVectors == null) {
                 throw new IllegalArgumentException("Document vectors path must be provided");
             }
-            if (dimensions <= 0) {
+            if (dimensions <= 0 && dimensions != -1) {
-                throw new IllegalArgumentException("dimensions must be a positive integer");
+                throw new IllegalArgumentException(
+                    "dimensions must be a positive integer or -1 for when dimension is available in the vector file"
+                );
             }
             return new CmdLineArgs(
                 docVectors,

qa/vector/src/main/java/org/elasticsearch/test/knn/KnnIndexTester.java

@@ -200,7 +200,7 @@ public class KnnIndexTester {
                     knnIndexer.numSegments(result);
                 }
             }
-            if (cmdLineArgs.queryVectors() != null) {
+            if (cmdLineArgs.queryVectors() != null && cmdLineArgs.numQueries() > 0) {
                 KnnSearcher knnSearcher = new KnnSearcher(indexPath, cmdLineArgs);
                 knnSearcher.runSearch(result);
             }

qa/vector/src/main/java/org/elasticsearch/test/knn/KnnIndexer.java

@@ -64,7 +64,7 @@ class KnnIndexer {
     private final Path docsPath;
     private final Path indexPath;
     private final VectorEncoding vectorEncoding;
-    private final int dim;
+    private int dim;
     private final VectorSimilarityFunction similarityFunction;
     private final Codec codec;
     private final int numDocs;
@@ -106,10 +106,6 @@ class KnnIndexer {
 
         iwc.setMaxFullFlushMergeWaitMillis(0);
 
-        FieldType fieldType = switch (vectorEncoding) {
-            case BYTE -> KnnByteVectorField.createFieldType(dim, similarityFunction);
-            case FLOAT32 -> KnnFloatVectorField.createFieldType(dim, similarityFunction);
-        };
         iwc.setInfoStream(new PrintStreamInfoStream(System.out) {
             @Override
             public boolean isEnabled(String component) {
@@ -137,7 +133,26 @@ class KnnIndexer {
             FileChannel in = FileChannel.open(docsPath)
         ) {
             long docsPathSizeInBytes = in.size();
-            if (docsPathSizeInBytes % ((long) dim * vectorEncoding.byteSize) != 0) {
+            int offsetByteSize = 0;
+            if (dim == -1) {
+                offsetByteSize = 4;
+                ByteBuffer preamble = ByteBuffer.allocate(4).order(ByteOrder.LITTLE_ENDIAN);
+                int bytesRead = Channels.readFromFileChannel(in, 0, preamble);
+                if (bytesRead < 4) {
+                    throw new IllegalArgumentException(
+                        "docsPath \"" + docsPath + "\" does not contain a valid dims?  size=" + docsPathSizeInBytes
+                    );
+                }
+                dim = preamble.getInt(0);
+                if (dim <= 0) {
+                    throw new IllegalArgumentException("docsPath \"" + docsPath + "\" has invalid dimension: " + dim);
+                }
+            }
+            FieldType fieldType = switch (vectorEncoding) {
+                case BYTE -> KnnByteVectorField.createFieldType(dim, similarityFunction);
+                case FLOAT32 -> KnnFloatVectorField.createFieldType(dim, similarityFunction);
+            };
+            if (docsPathSizeInBytes % (((long) dim * vectorEncoding.byteSize + offsetByteSize)) != 0) {
                 throw new IllegalArgumentException(
                     "docsPath \"" + docsPath + "\" does not contain a whole number of vectors?  size=" + docsPathSizeInBytes
                 );
@@ -150,7 +165,7 @@ class KnnIndexer {
                 vectorEncoding.byteSize
             );
 
-            VectorReader inReader = VectorReader.create(in, dim, vectorEncoding);
+            VectorReader inReader = VectorReader.create(in, dim, vectorEncoding, offsetByteSize);
             try (ExecutorService exec = Executors.newFixedThreadPool(numIndexThreads, r -> new Thread(r, "KnnIndexer-Thread"))) {
                 AtomicInteger numDocsIndexed = new AtomicInteger();
                 List<Future<?>> threads = new ArrayList<>();
@@ -271,21 +286,24 @@ class KnnIndexer {
 
     static class VectorReader {
         final float[] target;
+        final int offsetByteSize;
         final ByteBuffer bytes;
         final FileChannel input;
         long position;
 
-        static VectorReader create(FileChannel input, int dim, VectorEncoding vectorEncoding) throws IOException {
+        static VectorReader create(FileChannel input, int dim, VectorEncoding vectorEncoding, int offsetByteSize) throws IOException {
+            // check if dim is set as preamble in the file:
             int bufferSize = dim * vectorEncoding.byteSize;
-            if (input.size() % ((long) dim * vectorEncoding.byteSize) != 0) {
+            if (input.size() % ((long) dim * vectorEncoding.byteSize + offsetByteSize) != 0) {
                 throw new IllegalArgumentException(
                     "vectors file \"" + input + "\" does not contain a whole number of vectors?  size=" + input.size()
                 );
             }
-            return new VectorReader(input, dim, bufferSize);
+            return new VectorReader(input, dim, bufferSize, offsetByteSize);
         }
 
-        VectorReader(FileChannel input, int dim, int bufferSize) throws IOException {
+        VectorReader(FileChannel input, int dim, int bufferSize, int offsetByteSize) throws IOException {
+            this.offsetByteSize = offsetByteSize;
             this.bytes = ByteBuffer.wrap(new byte[bufferSize]).order(ByteOrder.LITTLE_ENDIAN);
             this.input = input;
             this.target = new float[dim];
@@ -293,14 +311,14 @@ class KnnIndexer {
         }
 
         void reset() throws IOException {
-            position = 0;
+            position = offsetByteSize;
             input.position(position);
         }
 
         private void readNext() throws IOException {
             int bytesRead = Channels.readFromFileChannel(this.input, position, bytes);
             if (bytesRead < bytes.capacity()) {
-                position = 0;
+                position = offsetByteSize;
                 bytes.position(0);
                 // wrap around back to the start of the file if we hit the end:
                 logger.warn("VectorReader hit EOF when reading " + this.input + "; now wrapping around to start of file again");
@@ -312,7 +330,7 @@ class KnnIndexer {
                     );
                 }
             }
-            position += bytesRead;
+            position += bytesRead + offsetByteSize;
             bytes.position(0);
         }
 

qa/vector/src/main/java/org/elasticsearch/test/knn/KnnSearcher.java

@@ -40,6 +40,7 @@ import org.apache.lucene.search.TotalHits;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.store.FSDirectory;
 import org.apache.lucene.store.MMapDirectory;
+import org.elasticsearch.common.io.Channels;
 import org.elasticsearch.core.PathUtils;
 import org.elasticsearch.index.mapper.vectors.DenseVectorFieldMapper;
 import org.elasticsearch.search.profile.query.QueryProfiler;
@@ -87,7 +88,7 @@ class KnnSearcher {
     private final int efSearch;
     private final int nProbe;
     private final KnnIndexTester.IndexType indexType;
-    private final int dim;
+    private int dim;
     private final VectorSimilarityFunction similarityFunction;
     private final VectorEncoding vectorEncoding;
     private final float overSamplingFactor;
@@ -117,6 +118,7 @@ class KnnSearcher {
         TopDocs[] results = new TopDocs[numQueryVectors];
         int[][] resultIds = new int[numQueryVectors][];
         long elapsed, totalCpuTimeMS, totalVisited = 0;
+        int offsetByteSize = 0;
         try (
             FileChannel input = FileChannel.open(queryPath);
             ExecutorService executorService = Executors.newFixedThreadPool(searchThreads, r -> new Thread(r, "KnnSearcher-Thread"))
@@ -128,7 +130,19 @@ class KnnSearcher {
                     + " bytes, assuming vector count is "
                     + (queryPathSizeInBytes / ((long) dim * vectorEncoding.byteSize))
             );
-            KnnIndexer.VectorReader targetReader = KnnIndexer.VectorReader.create(input, dim, vectorEncoding);
+            if (dim == -1) {
+                offsetByteSize = 4;
+                ByteBuffer preamble = ByteBuffer.allocate(4).order(ByteOrder.LITTLE_ENDIAN);
+                int bytesRead = Channels.readFromFileChannel(input, 0, preamble);
+                if (bytesRead < 4) {
+                    throw new IllegalArgumentException("queryPath \"" + queryPath + "\" does not contain a valid dims?");
+                }
+                dim = preamble.getInt(0);
+                if (dim <= 0) {
+                    throw new IllegalArgumentException("queryPath \"" + queryPath + "\" has invalid dimension: " + dim);
+                }
+            }
+            KnnIndexer.VectorReader targetReader = KnnIndexer.VectorReader.create(input, dim, vectorEncoding, offsetByteSize);
             long startNS;
             try (MMapDirectory dir = new MMapDirectory(indexPath)) {
                 try (DirectoryReader reader = DirectoryReader.open(dir)) {
@@ -191,7 +205,7 @@ class KnnSearcher {
             }
         }
         logger.info("checking results");
-        int[][] nn = getOrCalculateExactNN();
+        int[][] nn = getOrCalculateExactNN(offsetByteSize);
         finalResults.avgRecall = checkResults(resultIds, nn, topK);
         finalResults.qps = (1000f * numQueryVectors) / elapsed;
         finalResults.avgLatency = (float) elapsed / numQueryVectors;
@@ -200,7 +214,7 @@ class KnnSearcher {
         finalResults.avgCpuCount = (double) totalCpuTimeMS / elapsed;
     }
 
-    private int[][] getOrCalculateExactNN() throws IOException {
+    private int[][] getOrCalculateExactNN(int vectorFileOffsetBytes) throws IOException {
         // look in working directory for cached nn file
         String hash = Integer.toString(
             Objects.hash(
@@ -228,9 +242,9 @@ class KnnSearcher {
             // checking low-precision recall
             int[][] nn;
             if (vectorEncoding.equals(VectorEncoding.BYTE)) {
-                nn = computeExactNNByte(queryPath);
+                nn = computeExactNNByte(queryPath, vectorFileOffsetBytes);
             } else {
-                nn = computeExactNN(queryPath);
+                nn = computeExactNN(queryPath, vectorFileOffsetBytes);
             }
             writeExactNN(nn, nnPath);
             long elapsedMS = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startNS); // ns -> ms
@@ -356,12 +370,17 @@ class KnnSearcher {
         }
     }
 
-    private int[][] computeExactNN(Path queryPath) throws IOException {
+    private int[][] computeExactNN(Path queryPath, int vectorFileOffsetBytes) throws IOException {
         int[][] result = new int[numQueryVectors][];
         try (Directory dir = FSDirectory.open(indexPath); DirectoryReader reader = DirectoryReader.open(dir)) {
             List<Callable<Void>> tasks = new ArrayList<>();
             try (FileChannel qIn = FileChannel.open(queryPath)) {
-                KnnIndexer.VectorReader queryReader = KnnIndexer.VectorReader.create(qIn, dim, VectorEncoding.FLOAT32);
+                KnnIndexer.VectorReader queryReader = KnnIndexer.VectorReader.create(
+                    qIn,
+                    dim,
+                    VectorEncoding.FLOAT32,
+                    vectorFileOffsetBytes
+                );
                 for (int i = 0; i < numQueryVectors; i++) {
                     float[] queryVector = new float[dim];
                     queryReader.next(queryVector);
@@ -373,12 +392,12 @@ class KnnSearcher {
         }
     }
 
-    private int[][] computeExactNNByte(Path queryPath) throws IOException {
+    private int[][] computeExactNNByte(Path queryPath, int vectorFileOffsetBytes) throws IOException {
         int[][] result = new int[numQueryVectors][];
         try (Directory dir = FSDirectory.open(indexPath); DirectoryReader reader = DirectoryReader.open(dir)) {
             List<Callable<Void>> tasks = new ArrayList<>();
             try (FileChannel qIn = FileChannel.open(queryPath)) {
-                KnnIndexer.VectorReader queryReader = KnnIndexer.VectorReader.create(qIn, dim, VectorEncoding.BYTE);
+                KnnIndexer.VectorReader queryReader = KnnIndexer.VectorReader.create(qIn, dim, VectorEncoding.BYTE, vectorFileOffsetBytes);
                 for (int i = 0; i < numQueryVectors; i++) {
                     byte[] queryVector = new byte[dim];
                     queryReader.next(queryVector);