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refactor!: rename the LSM table APIs to MemWAL

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The write path these APIs drive is Lance's MemWAL, and "LSM" described
its shape rather than naming it. The surface now says MemWAL, and turning
it on and off reads as enabling a feature rather than installing a spec.

| Before | After |
|---|---|
| `set_lsm_write_spec` | `enable_memwal` |
| `unset_lsm_write_spec` | `disable_memwal` |
| `get_lsm_write_spec` | `get_memwal_spec` |
| `flush_lsm` / `compact_lsm` / `checkpoint_lsm` | `flush_memwal` / `compact_memwal` / `checkpoint_memwal` |
| `get_lsm_stats` | `get_memwal_stats` |
| `close_lsm_writers` | `close_memwal_writers` |
| `use_lsm` (query, merge insert) | `use_memwal` |
| `LsmWriteSpec` / `LsmStats` | `MemWalWriteSpec` / `MemWalStats` |
| Java `LanceDbTableLsm` | `LanceDbTableMemWal` |

TypeScript and Java use camelCase (`enableMemWal`, `getMemWalStats`,
...); the napi methods set `js_name` so the generated names keep the
`MemWal` casing. The flush/compact/checkpoint methods keep a `_memwal`
suffix so `compact_memwal` is not confused with `compact_files` and
`optimize`, which compact the base table.

## Wire

The remote routes and JSON envelopes move with the SDKs and must ship
together with the matching server change:

- `/set_lsm_write_spec/` -> `/enable_memwal/`, `/unset_lsm_write_spec/`
  -> `/disable_memwal/`, `/get_lsm_write_spec/` -> `/get_memwal_spec/`,
  `/flush_lsm/`, `/compact_lsm/`, `/get_lsm_stats/` -> `*_memwal/`
- response keys `lsm_write_spec` -> `memwal_spec`, `lsm_stats` ->
  `memwal_stats`; query and merge-insert body field `use_lsm` ->
  `use_memwal`

## Also fixed

The previous rename turned the Java `bucket` sharding mode into
`tableShard` in the javadoc example and tests, and the test fixtures
sent `tableShards` where the parser reads `table_shards`, so the Java
tests did not compile. Both are restored.

Internal names (`LsmMode`, `LsmScanner`, the `merge::lsm` and
`query::lsm` modules) are unchanged.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
This commit is contained in:
Daniel Rammer
2026-10-12 15:54:03 -05:00
co-authored by Claude Opus 5.5
parent 06d7f82fa2
commit d7e921dbec
62 changed files with 1349 additions and 1360 deletions
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java/README.md
+7 -7
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@@ -29,7 +29,7 @@ LanceNamespace namespaceClient = LanceDbNamespaceClientBuilder.newBuilder()
.build();
```
## MemWAL LSM write path
## MemWAL write path
Most table operations reach LanceDB through the `LanceNamespace` above, which is
generated from the Lance Namespace specification. The MemWAL LSM routes are not part
@@ -37,26 +37,26 @@ of that specification, so they are issued through a separate client:
```java
import com.lancedb.LanceDbRestClient;
import com.lancedb.LanceDbTableLsm;
import com.lancedb.LsmWriteSpec;
import com.lancedb.LanceDbTableMemWal;
import com.lancedb.MemWalWriteSpec;
LanceDbRestClient client = LanceDbNamespaceClientBuilder.newBuilder()
.apiKey("your_lancedb_cloud_api_key")
.database("your_database_name")
.buildRestClient();
LanceDbTableLsm lsm = new LanceDbTableLsm(client, "my_table");
LanceDbTableMemWal memWal = new LanceDbTableMemWal(client, "my_table");
// Route future merge_insert upserts through the MemWAL, hash-bucketed by `id`.
lsm.setLsmWriteSpec(LsmWriteSpec.bucket("id", 16));
memWal.enableMemWal(MemWalWriteSpec.bucket("id", 16));
// ... merge_insert traffic ...
// Converge the fresh tier into the base table.
lsm.checkpointLsm();
memWal.checkpointMemWal();
// Inspect live per-table-shard state.
lsm.getLsmStats().ifPresent(stats -> stats.tableShards().forEach(tableShard ->
memWal.getMemWalStats().ifPresent(stats -> stats.tableShards().forEach(tableShard ->
System.out.println(tableShard.shardId() + ": " + tableShard.sstables().size() + " SSTables")));
client.close();