Implementation:Lance format Lance Java OptimizeOptions

Knowledge Sources	Lance
Domains	Java_SDK, Indexing
Last Updated	2026-02-08 19:33 GMT

Overview

Description

OptimizeOptions is a Java class in the org.lance.index package that defines options for optimizing indices on a Lance dataset. It mirrors the behavior of lance_index::optimize::OptimizeOptions in Rust. The class supports configuring the number of indices to merge per index name, restricting optimization to specific index names, and choosing between incremental merge and full retraining. All fields except retrain are optional, with defaults delegated to the Rust implementation.

Usage

OptimizeOptions is constructed via OptimizeOptions.builder() and passed to dataset optimize-indices APIs. When no index names are provided, all user indices are considered (system indices are always excluded).

Code Reference

Source Location

java/src/main/java/org/lance/index/OptimizeOptions.java

Signature

public class OptimizeOptions {
    public static Builder builder();

    public Optional<Integer> getNumIndicesToMerge();
    public Optional<List<String>> getIndexNames();
    public boolean isRetrain();

    public static class Builder {
        public Builder numIndicesToMerge(int numIndicesToMerge);
        public Builder indexNames(List<String> indexNames);
        public Builder retrain(boolean retrain);
        public OptimizeOptions build();
    }
}

Import

import org.lance.index.OptimizeOptions;

I/O Contract

Builder Inputs

Parameter	Type	Required	Default	Description
numIndicesToMerge	int	No	Optional.empty() (Rust default)	Number of indices to merge per index name
indexNames	List<String>	No	Optional.empty() (all user indices)	Names of indices to optimize; if empty, all user indices are considered
retrain	boolean	No	false	Whether to retrain the index instead of incremental merge

Accessor Outputs

Method	Return Type	Description
getNumIndicesToMerge()	Optional<Integer>	Number of indices to merge, if set
getIndexNames()	Optional<List<String>>	Index names to optimize, if restricted
isRetrain()	boolean	Whether retraining is enabled

Usage Examples

import org.lance.index.OptimizeOptions;
import java.util.Arrays;

// Optimize all indices with default merge settings
OptimizeOptions defaultOptions = OptimizeOptions.builder().build();

// Optimize specific indices with incremental merge
OptimizeOptions mergeOptions = OptimizeOptions.builder()
    .indexNames(Arrays.asList("embedding_idx", "category_idx"))
    .numIndicesToMerge(5)
    .build();

// Retrain a specific index from scratch
OptimizeOptions retrainOptions = OptimizeOptions.builder()
    .indexNames(Arrays.asList("embedding_idx"))
    .retrain(true)
    .build();

Related Pages

• Index - Index metadata that may be optimized
• IndexOptions - Options for creating indices (complementary to optimization)
• IndexDescription - Describes indices that can be targets for optimization