Question: problem reading and writing to index.

[rzorzorzo]

hello,

i am trying to read and write the index and the vectors from/to file.
here my code:

`
public static void write() throws Exception {
OnHeapGraphIndex index = (OnHeapGraphIndex) builder.getGraph();
var featureId = FeatureId.INLINE_VECTORS;
var inlineVectors = new InlineVectors(dimension);

	IntFunction<Feature.State> vectorSupplier = ordinal -> {
		VectorFloat<?> vector = vectorValues.getVector(ordinal);
		return new InlineVectors.State(vector);
	};

	try (var writer = new OnDiskGraphIndexWriter.Builder(index, indexPath).with(inlineVectors) 
			.build()) {
		Map<FeatureId, IntFunction<Feature.State>> suppliers = Map.of(featureId, vectorSupplier);
		writer.write(suppliers);
	}
}

public static void readIndex() throws Exception {
	if (!indexPath.toFile().exists())
		return;
	try (ReaderSupplier readerSupplier = ReaderSupplierFactory.open(indexPath)) {
		OnDiskGraphIndex oldIndex = OnDiskGraphIndex.load(readerSupplier);
		Map<FeatureId, ? extends Feature> features = oldIndex.getFeatures();
		InlineVectors ivFeature  = (InlineVectors) oldIndex.getFeatures().get(FeatureId.INLINE_VECTORS);
		//?? 
		builder = new GraphIndexBuilder(scoreProvider, dimension, 16, 100, 1.2f, 1.2f, true);
	}
}

`
Question: how to reconstruct MapRandomAccessVectorValues from InlineVectors ?

[rzorzorzo]

PS: it is also unclear how to read a builder from disk, so that it is mutable:

builder.load(new SimpleReader(indexPath));
is deprecated.

OnDiskGraphIndex index = OnDiskGraphIndex.load(rs);
is immutable.

[rzorzorzo]

PS: 4.0.0-rc.8

[ashkrisk]

@rzorzorzo we somewhat recently added a set of introductory tutorials. In this case you might find the DiskIntro tutorial helpful.

---

How to reconstruct MapRandomAccessVectorValues from InlineVectors?

I guess you're more interested in getting in a RandomAccessVectorValues from an OnDiskGraphIndex. You can do this in two steps: (1) create a GraphSearcher for the disk graph, then (2) extract a RAVV from the searcher. See this section of the DiskIntro example:

jvector/jvector-examples/src/main/java/io/github/jbellis/jvector/example/tutorial/DiskIntro.java

Lines 111 to 115 in c059e86

	try (GraphSearcher searcher = new GraphSearcher(graph)) {
	// Views of an OnDiskGraphIndex with inline or separated vectors can be used as RAVVs!
	// In multi-threaded scenarios you should have one searcher per thread
	// and extract a view for each thread from the associated searcher.
	var graphRavv = (RandomAccessVectorValues) searcher.getView();

---

it is also unclear how to read a builder from disk, so that it is mutable

The OnDiskGraphIndex is immutable by design. If you want to change a graph once you've saved it to disk, you should probably perform some kind of compaction. We've just added support for this in JVector, here's the relevant documentation.