Implementation:Lance format Lance Java ScalarIndexParams

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

Overview

Description

ScalarIndexParams is a Java class in the org.lance.index.scalar package that holds parameters for creating scalar indices in Lance. It consists of an index type string (e.g., "btree", "zonemap", "bitmap", "inverted", "labellist", "ngram") and an optional JSON string containing type-specific parameters. The class provides both static factory methods (create) and a Builder for construction.

Usage

ScalarIndexParams is typically not constructed directly by end users. Instead, specialized builder classes such as BTreeIndexParams, InvertedIndexParams, and ZoneMapIndexParams produce ScalarIndexParams instances. However, the static create() methods allow direct construction for index types without dedicated builders.

Code Reference

Source Location

java/src/main/java/org/lance/index/scalar/ScalarIndexParams.java

Signature

public class ScalarIndexParams {
    public static ScalarIndexParams create(String indexType);
    public static ScalarIndexParams create(String indexType, String jsonParams);

    public String getIndexType();
    public Optional<String> getJsonParams();

    public static class Builder {
        public Builder(String indexType);
        public Builder setJsonParams(String jsonParams);
        public ScalarIndexParams build();
    }
}

Import

import org.lance.index.scalar.ScalarIndexParams;

I/O Contract

Factory / Builder Inputs

Parameter	Type	Required	Default	Description
indexType	String	Yes	N/A	The scalar index type identifier (e.g., "btree", "zonemap", "bitmap", "inverted", "labellist", "ngram")
jsonParams	String	No	Optional.empty()	JSON string containing index-specific parameters

Accessor Outputs

Method	Return Type	Description
getIndexType()	String	The index type identifier string
getJsonParams()	Optional<String>	Optional JSON parameters string

Usage Examples

import org.lance.index.scalar.ScalarIndexParams;
import org.lance.index.IndexParams;

// Create a simple bitmap index with no extra parameters
ScalarIndexParams bitmap = ScalarIndexParams.create("bitmap");

// Create a label list index with no extra parameters
ScalarIndexParams labelList = ScalarIndexParams.create("labellist");

// Create a scalar index with custom JSON parameters
ScalarIndexParams custom = ScalarIndexParams.create(
    "btree",
    "{\"zone_size\": 2048}"
);

// Access the index type and params
System.out.println(bitmap.getIndexType());           // "bitmap"
System.out.println(custom.getJsonParams().get());     // {"zone_size": 2048}

// Use via IndexParams
IndexParams params = IndexParams.builder()
    .setScalarIndexParams(bitmap)
    .build();

// Or use the Builder directly
ScalarIndexParams viaBuilder = new ScalarIndexParams.Builder("ngram")
    .setJsonParams("{\"min_ngram_length\": 2}")
    .build();

Related Pages

• BTreeIndexParams - Builder that produces ScalarIndexParams for B-Tree indices
• InvertedIndexParams - Builder that produces ScalarIndexParams for inverted indices
• ZoneMapIndexParams - Builder that produces ScalarIndexParams for zone map indices
• IndexParams - Top-level container that holds ScalarIndexParams