Files
lancedb/java/README.md
T
Dan RammerandClaude Opus 5.5 92825f6f13 refactor!: rename MemWAL APIs to RTE (realtime engine) (#4598)
## What

Renames the user-facing MemWAL surface to **RTE** (realtime engine)
across Rust, Python, TypeScript, and Java, including the REST wire
format. This follows the LSM → MemWAL rename in #4075.

| Before | After |
|---|---|
| `MemWalWriteSpec` / `MemWalStats` | `RTEWriteSpec` / `RTEStats` |
| `enable_memwal` / `disable_memwal` / `get_memwal_spec` | `enable_rte`
/ `disable_rte` / `get_rte_spec` |
| `flush_memwal` / `compact_memwal` / `checkpoint_memwal` | `flush_rte`
/ `compact_rte` / `checkpoint_rte` |
| `get_memwal_stats` / `close_memwal_writers` | `get_rte_stats` /
`close_rte_writers` |
| `use_memwal` (query, merge insert) | `use_rte` |
| TS/Java `enableMemWal`, `useMemWal`, ... | `enableRTE`, `useRTE`, ...
(napi `js_name` set explicitly) |
| Java `LanceDbTableMemWal` | `LanceDbTableRTE` |
| `table/memwal_stats.rs` | `table/rte_stats.rs` |

Docs and comments now say "realtime engine (RTE)". Text about Lance's
underlying mechanism keeps "MemWAL" ("Lance's MemWAL", "MemWAL index").

**Left alone:** Lance-owned names (`MemWalIndexDetails`,
`DatasetMemWalExt`, `InitializeMemWal*`, `mem_wal` paths), internal
`Lsm*` names and modules, and the `does not support with_row_id` refusal
text that the hybrid fallback matches on.

## Compatibility

Breaking, for an experimental API. The wire format changes, so this must
roll out together with the matching sophon change (lancedb/sophon#8870):

- Routes: `/enable_memwal/` → `/enable_rte/`, `/disable_memwal/` →
`/disable_rte/`, `/get_memwal_spec/` → `/get_rte_spec/`,
`/get_memwal_stats/` → `/get_rte_stats/`, `/flush_memwal/` →
`/flush_rte/`, `/compact_memwal/` → `/compact_rte/`
- Response keys: `memwal_spec` → `rte_spec`, `memwal_stats` →
`rte_stats`
- Request field: `use_memwal` → `use_rte` on query and merge-insert
bodies

The SQL keyword becomes `ALTER TABLE ... SET RTE` server-side. The
guides under `docs/web` will be updated separately.

## Validation

- Rust: `cargo clippy --features remote --tests --examples` clean;
`cargo test --features remote -p lancedb --lib`: 1533 passed
- Java: `mvn test`: 37 passed (Spotless applied with JDK 11)
- Python: `ruff format` / `ruff check` clean; targeted tests
(`test_rte_spec`, `test_merge_insert_lsm`, `test_remote_db`,
`test_wal_hybrid`, `test_query`, `test_permutation`, `test_table`): 708
passed
- TypeScript: `pnpm build`; `table`, `query` tests: 606 passed; `biome
check` clean; `docs/src/js` regenerated with `pnpm run docs`

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
2026-10-20 11:58:57 -05:00

92 lines
2.6 KiB
Markdown

# LanceDB Java Enterprise Client
## Configuration and Initialization
### LanceDB Cloud
For LanceDB Cloud, use the simplified builder API:
```java
import com.lancedb.LanceDbNamespaceClientBuilder;
import org.lance.namespace.LanceNamespace;
// If your DB url is db://example-db, then your database here is example-db
LanceNamespace namespaceClient = LanceDbNamespaceClientBuilder.newBuilder()
.apiKey("your_lancedb_cloud_api_key")
.database("your_database_name")
.build();
```
### LanceDB Enterprise
For Enterprise deployments, use your custom endpoint:
```java
LanceNamespace namespaceClient = LanceDbNamespaceClientBuilder.newBuilder()
.apiKey("your_lancedb_enterprise_api_key")
.database("your_database_name")
.endpoint("<your_enterprise_endpoint>")
.build();
```
## RTE write path
Most table operations reach LanceDB through the `LanceNamespace` above, which is
generated from the Lance Namespace specification. The RTE LSM routes are not part
of that specification, so they are issued through a separate client:
```java
import com.lancedb.LanceDbRestClient;
import com.lancedb.LanceDbTableRTE;
import com.lancedb.RTEWriteSpec;
LanceDbRestClient client = LanceDbNamespaceClientBuilder.newBuilder()
.apiKey("your_lancedb_cloud_api_key")
.database("your_database_name")
.buildRestClient();
LanceDbTableRTE rte = new LanceDbTableRTE(client, "my_table");
// Route future merge_insert upserts through the RTE, hash-bucketed by `id`.
rte.enableRTE(RTEWriteSpec.bucket("id", 16));
// ... merge_insert traffic ...
// Converge the fresh tier into the base table.
rte.checkpointRTE();
// Inspect live per-table-shard state.
rte.getRTEStats().ifPresent(stats -> stats.tableShards().forEach(tableShard ->
System.out.println(tableShard.shardId() + ": " + tableShard.sstables().size() + " SSTables")));
client.close();
```
`maintainedIndexes` is tri-state, and the null default is the opposite of what a Java
reader usually expects:
| Value | Meaning |
| --- | --- |
| unset (null) | Maintain **every** index the table has, including ones created later |
| `Collections.emptyList()` | Maintain **none** |
| `Arrays.asList("id_idx")` | Maintain exactly those |
## Development
The parent POM includes `https://maven.lance.org` to resolve Lance beta and RC
dependencies. Use an explicit `lance-core.version`; numbered beta and RC versions
are Maven releases, not snapshots. Maven Central remains available for stable
and historical versions, as well as other dependencies.
Build:
```shell
./mvnw install -pl lancedb-core -am
```
Run tests:
```shell
./mvnw test -pl lancedb-core
```