Implementation:Apache Shardingsphere MemoryRepository Persist

Knowledge Sources	Apache_Shardingsphere
Domains	Persistence, Standalone
Last Updated	2026-02-10 00:00 GMT

Overview

MemoryRepository is an in-memory standalone persist repository using a TreeMap for hierarchical key-value storage without durability.

Description

MemoryRepository implements StandalonePersistRepository with a simple TreeMap<String, String> backing store. The query method returns the value directly from the map. getChildrenKeys uses TreeMap.subMap with a search prefix to efficiently find all entries under a parent path, extracts the immediate child segment by finding the next slash after the prefix, deduplicates, and filters empty results. isExisted checks containsKey. persist puts the key-value pair unconditionally. update puts only if the key already exists. delete removes the exact key. The close method is a no-op. It is registered as the default standalone repository type (isDefault returns true) with type "Memory".

Usage

Use this repository for testing, development, or lightweight standalone scenarios where metadata persistence across restarts is not required. It is the default repository when no explicit repository type is configured in standalone mode.

Code Reference

Source Location

• Repository: Apache_Shardingsphere
• File: MemoryRepository.java
• Lines: 1-99

Signature

public final class MemoryRepository implements StandalonePersistRepository {

    public String query(final String key)

    public List<String> getChildrenKeys(final String key)

    public boolean isExisted(final String key)

    public void persist(final String key, final String value)

    public void update(final String key, final String value)

    public void delete(final String key)

    public void close()

    public Object getType()

    public boolean isDefault()
}

Import

import org.apache.shardingsphere.mode.repository.standalone.memory.MemoryRepository;

I/O Contract

Inputs

Name	Type	Required	Description
key	String	Yes	Hierarchical path key for all operations
value	String	Yes	Data value for persist and update operations

Outputs

Name	Type	Description
queryResult	String	Value at the key, or null if not found
childrenKeys	List<String>	Immediate child key names under the parent path
isExisted	boolean	Whether the key exists in the TreeMap

Usage Examples

MemoryRepository repository = new MemoryRepository();

// Persist data
repository.persist("/metadata/my_db/rules/sharding", "sharding_config_yaml");

// Query data
String config = repository.query("/metadata/my_db/rules/sharding");

// List children
List<String> children = repository.getChildrenKeys("/metadata/my_db/rules");
// Returns: ["sharding"]

// Update existing data
repository.update("/metadata/my_db/rules/sharding", "updated_config_yaml");

// Delete
repository.delete("/metadata/my_db/rules/sharding");

Related Pages

• Principle:Apache_Shardingsphere_Metadata_Repository_Persistence