refactor(lsm): rename LSM stats to SSTable and table shard

Aligns the LSM stats surface with the MemWAL naming settled upstream in
lance-format/lance#7943 and #7957, where the persisted unit became an
SSTable. Two terms in this API predate that pass.

**Generation -> SSTable.** A `GenerationStats` describes one flushed
MemTable, which is an SSTable. The generation *number* is kept — an
SSTable is identified by its generation — so only the noun moved.

**Bucket -> table shard.** Each entry is one MemWAL shard. "Bucket" names
only the hash sharding transform, so it was wrong for `identity` and
`year` sharding, which produce shards and no buckets at all.

| Before | After |
|---|---|
| `GenerationStats` | `SsTableStats` |
| `BucketStats` | `TableShardStats` |
| `LsmStats.buckets` | `LsmStats.table_shards` |
| `BucketStats.generations` | `TableShardStats.sstables` |
| `include_generation_rows` | `include_sstable_rows` |
| `newest_generation` | `newest_sstable_generation` |
| `outstanding_generations` | `outstanding_sstables` |

Applied across Rust, Python, TypeScript, and Java, including the
`get_lsm_stats` JSON field names. `LsmWriteSpec::Bucket` and `num_buckets`
are unchanged — those name the sharding transform, not the shard.

## Compatibility

Breaking for the MemWAL LSM stats API, which is experimental and paired
with a server that renames the same fields. The JSON keys `table_shards`
and `sstables` must roll out together with the WAL server change.

## Validation

- `cargo check -p lancedb --all-features`, `cargo fmt --all`
- `ruff format --check` and `ruff check` on the touched Python
- `biome check` on the touched TypeScript

The typedoc markdown under `docs/src/js` was updated by hand, not
regenerated: `npm run docs` needs the napi-built `./native` types. Worth
running `npm run docs` on this branch to confirm the generator agrees.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HgVf5C2yRbwK6pe1aMYkmg

java/lancedb-core/src/main/java/com/lancedb/LanceDbTableLsm.java

@@ -26,7 +26,7 @@ import java.util.OptionalLong;
  *
  * <p>Installing an {@link LsmWriteSpec} routes {@code mergeInsert} upserts through Lance's MemWAL —
  * an LSM-style append — instead of the standard merge path. Rows land in an in-memory memtable,
- * seal into L0 generations, and are merged into the base table by compaction.
+ * freeze into SSTables, and are merged into the base table by compaction.
  *
  * <p>These routes are not part of the Lance Namespace specification, so they are issued directly
  * rather than through {@link org.lance.namespace.LanceNamespace}.
@@ -38,7 +38,7 @@ import java.util.OptionalLong;
  *     .buildRestClient();
  *
  * LanceDbTableLsm lsm = new LanceDbTableLsm(client, "my_table");
- * lsm.setLsmWriteSpec(LsmWriteSpec.bucket("id", 16));
+ * lsm.setLsmWriteSpec(LsmWriteSpec.tableShard("id", 16));
  * // ... merge_insert traffic ...
  * lsm.checkpointLsm();
  * }</pre>
@@ -94,7 +94,7 @@ public class LanceDbTableLsm {
    * Install an {@link LsmWriteSpec} on this table, selecting the MemWAL LSM write path for future
    * {@code mergeInsert} calls.
    *
-   * <p>All variants require the table to have an unenforced primary key; bucket sharding
+   * <p>All variants require the table to have an unenforced primary key; tableShard sharding
    * additionally requires it to be the single column being bucketed.
    */
   public void setLsmWriteSpec(LsmWriteSpec spec) {
@@ -130,7 +130,7 @@ public class LanceDbTableLsm {
   }
 
   /**
-   * Seal every bucket's active memtable into a new L0 generation.
+   * Freeze every table shard's active memtable into a new SSTable.
    *
    * <p>Returns once the seal is committed. Sealing an empty memtable is a no-op, so this is safe to
    * call repeatedly.
@@ -140,7 +140,7 @@ public class LanceDbTableLsm {
   }
 
   /**
-   * Trigger a background L0 → base compaction pass per bucket.
+   * Trigger a background SSTable compaction pass per table shard.
    *
    * <p>Returns once the passes are <em>dispatched</em>, not once they finish — watch {@link
    * #getLsmStats}, or use {@link #checkpointLsm} to wait for convergence.
@@ -150,9 +150,9 @@ public class LanceDbTableLsm {
   }
 
   /**
-   * Read live per-bucket LSM state.
+   * Read live per-tableShard LSM state.
    *
-   * <p>Answers "how far behind is my fresh tier", "which bucket is hot", and "why is my fresh-tier
+   * <p>Answers "how far behind is my fresh tier", "which tableShard is hot", and "why is my fresh-tier
    * vector search brute-force". Mutates no table state.
    *
    * <p>Empty only when the LSM write path is not enabled — that is, when the server sends an absent
@@ -160,13 +160,13 @@ public class LanceDbTableLsm {
    * one throws rather than decoding to something empty, because {@link #checkpointLsm} reads
    * convergence out of these numbers and cannot tell a defaulted array from a drained one.
    *
-   * @param includeGenerationRows Also count rows per L0 generation. Off by default because each
+   * @param includeSstableRows Also count rows per SSTable. Off by default because each
    *     count opens an uncached Lance dataset.
    * @throws IllegalStateException if the response is absent or does not decode.
    */
-  public Optional<LsmStats> getLsmStats(boolean includeGenerationRows) {
+  public Optional<LsmStats> getLsmStats(boolean includeSstableRows) {
     Map<String, Object> body = new LinkedHashMap<String, Object>();
-    body.put("include_generation_rows", includeGenerationRows);
+    body.put("include_sstable_rows", includeSstableRows);
     JsonNode response = client.post(route("get_lsm_stats"), body);
     if (response == null) {
       throw new IllegalStateException("get_lsm_stats returned an empty response body");
@@ -186,8 +186,8 @@ public class LanceDbTableLsm {
   /**
    * Converge this table's LSM write path into its base table.
    *
-   * <p>Seals once, fixes a target watermark from the resulting L0, then triggers compaction and
-   * polls until that L0 is gone. The target set is fixed at the start, so generations created
+   * <p>Freezes once, fixes a target watermark from the resulting SSTables, then triggers compaction and
+   * polls until those SSTables are gone. The target set is fixed at the start, so sstables created
    * <em>during</em> the checkpoint are ignored — that is what lets it terminate under write load,
    * and what makes it best-effort: it converges the fresh tier as of some instant. Idempotent,
    * abandonable at any point, safe on a cadence.
@@ -204,7 +204,7 @@ public class LanceDbTableLsm {
     for (int reissue = 0; reissue <= MAX_REISSUES; reissue++) {
       // The seal turns everything written before this call into a generation, so the
       // watermark has to be read after it. Idempotent: sealing an empty memtable is a
-      // no-op, so a re-issue does not churn empty generations.
+      // no-op, so a re-issue does not churn empty sstables.
       if (issueVoid(this::flushLsm)) {
         backoff(reissue);
         continue;
@@ -220,7 +220,7 @@ public class LanceDbTableLsm {
         return;
       }
 
-      Map<String, Long> targets = newestGenerations(stats.value.get());
+      Map<String, Long> targets = newestSstableGenerations(stats.value.get());
       if (targets.isEmpty()) {
         return;
       }
@@ -236,7 +236,7 @@ public class LanceDbTableLsm {
   }
 
   /**
-   * Trigger and poll until no bucket holds a generation at or below its target.
+   * Trigger and poll until no tableShard holds a generation at or below its target.
    *
    * @return true when the drain finished, false when the table needs re-claiming from flush.
    */
@@ -250,21 +250,21 @@ public class LanceDbTableLsm {
         return true;
       }
 
-      // `compacting` is the bucket's compaction latch, held from dispatch until the pass
+      // `compacting` is the tableShard's compaction latch, held from dispatch until the pass
       // ends — including while it waits on a pod-wide permit. So it answers one question
       // only: do not pile on. Buckets with nothing outstanding are skipped, not counted
       // as idle.
       long outstanding = 0;
       boolean allCompacting = true;
-      for (BucketStats bucket : stats.value.get().buckets()) {
-        Long target = targets.get(bucket.shardId());
+      for (TableShardStats tableShard : stats.value.get().tableShards()) {
+        Long target = targets.get(tableShard.shardId());
         if (target == null) {
           continue;
         }
-        long remaining = bucket.outstandingGenerations(target);
+        long remaining = tableShard.outstandingSstables(target);
         if (remaining > 0) {
           outstanding += remaining;
-          allCompacting &= bucket.compacting();
+          allCompacting &= tableShard.compacting();
         }
       }
       if (outstanding == 0) {
@@ -281,7 +281,7 @@ public class LanceDbTableLsm {
           if (!isRetryable(e)) {
             throw e;
           }
-          // A 429 here means the server could latch no bucket at all, which the poll
+          // A 429 here means the server could latch no tableShard at all, which the poll
           // above already handles. Not retried in place: the latch it would contend for
           // is the one doing the work, so fall through and re-read — POLL_INTERVAL_MS is
           // the backoff.
@@ -291,13 +291,13 @@ public class LanceDbTableLsm {
     }
   }
 
-  /** The newest generation held by each bucket, skipping buckets holding none. */
-  private static Map<String, Long> newestGenerations(LsmStats stats) {
+  /** The newest generation held by each tableShard, skipping tableShards holding none. */
+  private static Map<String, Long> newestSstableGenerations(LsmStats stats) {
     Map<String, Long> targets = new HashMap<String, Long>();
-    for (BucketStats bucket : stats.buckets()) {
-      OptionalLong newest = bucket.newestGeneration();
+    for (TableShardStats tableShard : stats.tableShards()) {
+      OptionalLong newest = tableShard.newestSstableGeneration();
       if (newest.isPresent()) {
-        targets.put(bucket.shardId(), newest.getAsLong());
+        targets.put(tableShard.shardId(), newest.getAsLong());
       }
     }
     return targets;

java/lancedb-core/src/main/java/com/lancedb/LsmStats.java

@@ -20,37 +20,37 @@ import java.util.Collections;
 import java.util.List;
 
 /**
- * Live per-bucket LSM state, as returned by {@link LanceDbTableLsm#getLsmStats()}.
+ * Live per-tableShard LSM state, as returned by {@link LanceDbTableLsm#getLsmStats()}.
  *
- * <p>Nothing here is derived: sums and differences (total L0 bytes, WAL lag) are the caller's to
+ * <p>Nothing here is derived: sums and differences (total SSTable bytes, WAL lag) are the caller's to
  * compute. There is no "LSM is off" shape — that case is an empty {@link java.util.Optional},
  * because a stats object of zeros would read as measurements.
  */
 public class LsmStats {
   private static final String CONTEXT = "lsm stats";
 
-  private final List<BucketStats> buckets;
+  private final List<TableShardStats> tableShards;
 
-  LsmStats(List<BucketStats> buckets) {
-    this.buckets = Collections.unmodifiableList(buckets);
+  LsmStats(List<TableShardStats> tableShards) {
+    this.tableShards = Collections.unmodifiableList(tableShards);
   }
 
-  /** One entry per bucket. */
-  public List<BucketStats> buckets() {
-    return buckets;
+  /** One entry per tableShard. */
+  public List<TableShardStats> tableShards() {
+    return tableShards;
   }
 
   static LsmStats fromJson(JsonNode node) {
     JsonFields.requiredObject(node, CONTEXT);
-    List<BucketStats> buckets = new ArrayList<BucketStats>();
-    for (JsonNode bucket : JsonFields.requiredArray(node, "buckets", CONTEXT)) {
-      buckets.add(BucketStats.fromJson(bucket));
+    List<TableShardStats> tableShards = new ArrayList<TableShardStats>();
+    for (JsonNode tableShard : JsonFields.requiredArray(node, "table_shards", CONTEXT)) {
+      tableShards.add(TableShardStats.fromJson(tableShard));
     }
-    return new LsmStats(buckets);
+    return new LsmStats(tableShards);
   }
 
   @Override
   public String toString() {
-    return "LsmStats{buckets=" + buckets + "}";
+    return "LsmStats{tableShards=" + tableShards + "}";
   }
 }

java/lancedb-core/src/main/java/com/lancedb/SsTableStats.java

@@ -17,21 +17,21 @@ import com.fasterxml.jackson.databind.JsonNode;
 
 import java.util.OptionalLong;
 
-/** One flushed L0 generation. */
-public class GenerationStats {
+/** One SSTable. */
+public class SsTableStats {
   private static final String CONTEXT = "generation stats";
 
   private final long generation;
   private final long bytes;
   private final Long rows;
 
-  GenerationStats(long generation, long bytes, Long rows) {
+  SsTableStats(long generation, long bytes, Long rows) {
     this.generation = generation;
     this.bytes = bytes;
     this.rows = rows;
   }
 
-  /** The generation number. Increases as memtables are sealed into L0. */
+  /** The generation number. Increases as memtables are frozen into SSTables. */
   public long generation() {
     return generation;
   }
@@ -42,16 +42,16 @@ public class GenerationStats {
   }
 
   /**
-   * Rows in this generation, present only when {@code includeGenerationRows} was requested. Off by
+   * Rows in this generation, present only when {@code includeSstableRows} was requested. Off by
    * default because each count opens an uncached Lance dataset.
    */
   public OptionalLong rows() {
     return rows == null ? OptionalLong.empty() : OptionalLong.of(rows);
   }
 
-  static GenerationStats fromJson(JsonNode node) {
+  static SsTableStats fromJson(JsonNode node) {
     JsonFields.requiredObject(node, CONTEXT);
-    return new GenerationStats(
+    return new SsTableStats(
         JsonFields.requiredLong(node, "generation", CONTEXT),
         JsonFields.requiredLong(node, "bytes", CONTEXT),
         JsonFields.optionalLong(node, "rows", CONTEXT));
@@ -59,6 +59,6 @@ public class GenerationStats {
 
   @Override
   public String toString() {
-    return "GenerationStats{generation=" + generation + ", bytes=" + bytes + ", rows=" + rows + "}";
+    return "SsTableStats{generation=" + generation + ", bytes=" + bytes + ", rows=" + rows + "}";
   }
 }

java/lancedb-core/src/main/java/com/lancedb/TableShardStats.java

@@ -22,11 +22,11 @@ import java.util.Optional;
 import java.util.OptionalLong;
 
 /**
- * Live state of one bucket. A table is N buckets on one node; flattening to a single number hides
- * the one hot bucket that is usually why someone opened this endpoint.
+ * Live state of one tableShard. A table is N tableShards on one node; flattening to a single number hides
+ * the one hot tableShard that is usually why someone opened this endpoint.
  */
-public class BucketStats {
-  private static final String CONTEXT = "bucket stats";
+public class TableShardStats {
+  private static final String CONTEXT = "tableShard stats";
 
   private final String shardId;
   private final String status;
@@ -35,11 +35,11 @@ public class BucketStats {
   private final long currentGeneration;
   private final long replayAfterWalEntryPosition;
   private final long walEntryPositionLastSeen;
-  private final List<GenerationStats> generations;
+  private final List<SsTableStats> sstables;
   private final boolean compacting;
   private final List<MemtableStats> memtables;
 
-  BucketStats(
+  TableShardStats(
       String shardId,
       String status,
       long writerEpoch,
@@ -47,7 +47,7 @@ public class BucketStats {
       long currentGeneration,
       long replayAfterWalEntryPosition,
       long walEntryPositionLastSeen,
-      List<GenerationStats> generations,
+      List<SsTableStats> sstables,
       boolean compacting,
       List<MemtableStats> memtables) {
     this.shardId = shardId;
@@ -57,12 +57,12 @@ public class BucketStats {
     this.currentGeneration = currentGeneration;
     this.replayAfterWalEntryPosition = replayAfterWalEntryPosition;
     this.walEntryPositionLastSeen = walEntryPositionLastSeen;
-    this.generations = Collections.unmodifiableList(generations);
+    this.sstables = Collections.unmodifiableList(sstables);
     this.compacting = compacting;
     this.memtables = memtables == null ? null : Collections.unmodifiableList(memtables);
   }
 
-  /** The shard this bucket writes. */
+  /** The shard this tableShard writes. */
   public String shardId() {
     return shardId;
   }
@@ -100,13 +100,13 @@ public class BucketStats {
     return walEntryPositionLastSeen;
   }
 
-  /** Flushed L0 generations not yet merged into the base table. */
-  public List<GenerationStats> generations() {
-    return generations;
+  /** SSTables not yet merged into the base table. */
+  public List<SsTableStats> sstables() {
+    return sstables;
   }
 
   /**
-   * Whether a pass owns this bucket's compaction latch right now. Says <em>a</em> driver is
+   * Whether a pass owns this tableShard's compaction latch right now. Says <em>a</em> driver is
    * running, not <em>whose</em>, and the latch is held from dispatch — including while the pass
    * queues for a pod-wide compactor permit. Read it as "do not pile on", never as "mine is
    * progressing".
@@ -115,15 +115,15 @@ public class BucketStats {
     return compacting;
   }
 
-  /** Oldest first, active last. Empty for a {@code "Sealed"} bucket, whose state is torn down. */
+  /** Oldest first, active last. Empty for a {@code "Sealed"} tableShard, whose state is torn down. */
   public Optional<List<MemtableStats>> memtables() {
     return Optional.ofNullable(memtables);
   }
 
-  /** The newest flushed generation, or empty when L0 is empty. */
-  OptionalLong newestGeneration() {
+  /** The newest SSTable generation, or empty when the tier is empty. */
+  OptionalLong newestSstableGeneration() {
     OptionalLong newest = OptionalLong.empty();
-    for (GenerationStats generation : generations) {
+    for (SsTableStats generation : sstables) {
       if (!newest.isPresent() || generation.generation() > newest.getAsLong()) {
         newest = OptionalLong.of(generation.generation());
       }
@@ -132,15 +132,15 @@ public class BucketStats {
   }
 
   /**
-   * How many generations at or below {@code target} are still in L0.
+   * How many SSTables at or below {@code target} are still uncompacted.
    *
    * <p>A count, not a boolean: one pass drains a bounded prefix rather than the whole target set,
    * so a boolean would read as "no progress" for every pass but the last. Compaction drains
    * oldest-first, so this decreases monotonically.
    */
-  long outstandingGenerations(long target) {
+  long outstandingSstables(long target) {
     long count = 0;
-    for (GenerationStats generation : generations) {
+    for (SsTableStats generation : sstables) {
       if (generation.generation() <= target) {
         count++;
       }
@@ -148,11 +148,11 @@ public class BucketStats {
     return count;
   }
 
-  static BucketStats fromJson(JsonNode node) {
+  static TableShardStats fromJson(JsonNode node) {
     JsonFields.requiredObject(node, CONTEXT);
-    List<GenerationStats> generations = new ArrayList<GenerationStats>();
-    for (JsonNode generation : JsonFields.requiredArray(node, "generations", CONTEXT)) {
-      generations.add(GenerationStats.fromJson(generation));
+    List<SsTableStats> sstables = new ArrayList<SsTableStats>();
+    for (JsonNode generation : JsonFields.requiredArray(node, "sstables", CONTEXT)) {
+      sstables.add(SsTableStats.fromJson(generation));
     }
 
     JsonNode memtablesNode = JsonFields.optionalArray(node, "memtables", CONTEXT);
@@ -164,7 +164,7 @@ public class BucketStats {
       }
     }
 
-    return new BucketStats(
+    return new TableShardStats(
         JsonFields.requiredText(node, "shard_id", CONTEXT),
         JsonFields.requiredText(node, "status", CONTEXT),
         JsonFields.requiredLong(node, "writer_epoch", CONTEXT),
@@ -172,21 +172,21 @@ public class BucketStats {
         JsonFields.requiredLong(node, "current_generation", CONTEXT),
         JsonFields.requiredLong(node, "replay_after_wal_entry_position", CONTEXT),
         JsonFields.requiredLong(node, "wal_entry_position_last_seen", CONTEXT),
-        generations,
+        sstables,
         JsonFields.requiredBoolean(node, "compacting", CONTEXT),
         memtables);
   }
 
   @Override
   public String toString() {
-    return "BucketStats{shardId="
+    return "TableShardStats{shardId="
         + shardId
         + ", status="
         + status
         + ", currentGeneration="
         + currentGeneration
-        + ", generations="
-        + generations
+        + ", sstables="
+        + sstables
         + ", compacting="
         + compacting
         + "}";

java/lancedb-core/src/test/java/com/lancedb/LanceDbTableLsmTest.java

@@ -132,10 +132,10 @@ public class LanceDbTableLsmTest {
     enqueue("set_lsm_write_spec", 200, "");
 
     lsm.setLsmWriteSpec(
-        LsmWriteSpec.bucket("id", 16).withMaintainedIndexes(Arrays.asList("id_idx")));
+        LsmWriteSpec.tableShard("id", 16).withMaintainedIndexes(Arrays.asList("id_idx")));
 
     JsonNode body = MAPPER.readTree(requestBodies.get(0));
-    assertEquals("bucket", body.get("sharding").get("mode").asText());
+    assertEquals("tableShard", body.get("sharding").get("mode").asText());
     assertEquals("id", body.get("sharding").get("column").asText());
     assertEquals(16, body.get("sharding").get("num_buckets").asInt());
     assertEquals(1, body.get("maintained_indexes").size());
@@ -201,7 +201,7 @@ public class LanceDbTableLsmTest {
     enqueue(
         "get_lsm_write_spec",
         200,
-        "{\"lsm_write_spec\":{\"sharding\":{\"mode\":\"bucket\",\"column\":\"id\","
+        "{\"lsm_write_spec\":{\"sharding\":{\"mode\":\"tableShard\",\"column\":\"id\","
             + "\"num_buckets\":16},\"maintained_indexes\":[\"id_idx\"],"
             + "\"writer_config_defaults\":{\"durable_write\":\"true\"}}}");
 
@@ -228,14 +228,14 @@ public class LanceDbTableLsmTest {
 
   @Test
   public void testGetLsmStats() throws Exception {
-    enqueue("get_lsm_stats", 200, stats(bucket("shard-0", false, 7L, 8L)));
+    enqueue("get_lsm_stats", 200, stats(tableShard("shard-0", false, 7L, 8L)));
 
     Optional<LsmStats> got = lsm.getLsmStats(true);
 
     assertEquals("/v1/table/my_table/get_lsm_stats/", requestPaths.get(0));
-    assertTrue(MAPPER.readTree(requestBodies.get(0)).get("include_generation_rows").asBoolean());
+    assertTrue(MAPPER.readTree(requestBodies.get(0)).get("include_sstable_rows").asBoolean());
     assertTrue(got.isPresent());
-    BucketStats decoded = got.get().buckets().get(0);
+    TableShardStats decoded = got.get().tableShards().get(0);
     assertEquals("shard-0", decoded.shardId());
     assertEquals("Active", decoded.status());
     assertEquals(1, decoded.writerEpoch());
@@ -243,8 +243,8 @@ public class LanceDbTableLsmTest {
     assertEquals(9, decoded.currentGeneration());
     assertFalse(decoded.compacting());
     assertEquals(Arrays.asList(7L, 8L), generationNumbers(decoded));
-    assertEquals(1024, decoded.generations().get(0).bytes());
-    assertFalse(decoded.generations().get(0).rows().isPresent(), "rows absent unless requested");
+    assertEquals(1024, decoded.sstables().get(0).bytes());
+    assertFalse(decoded.sstables().get(0).rows().isPresent(), "rows absent unless requested");
     assertFalse(decoded.memtables().isPresent(), "absent memtables stay absent");
   }
 
@@ -254,19 +254,19 @@ public class LanceDbTableLsmTest {
     enqueue(
         "get_lsm_stats",
         200,
-        "{\"lsm_stats\":{\"buckets\":[{\"shard_id\":\"shard-0\",\"status\":\"Active\","
+        "{\"lsm_stats\":{\"tableShards\":[{\"shard_id\":\"shard-0\",\"status\":\"Active\","
             + "\"writer_epoch\":1,\"manifest_version\":2,\"current_generation\":9,"
             + "\"replay_after_wal_entry_position\":3,\"wal_entry_position_last_seen\":11,"
-            + "\"generations\":[{\"generation\":7,\"bytes\":1024,\"rows\":42}],"
+            + "\"sstables\":[{\"generation\":7,\"bytes\":1024,\"rows\":42}],"
             + "\"compacting\":true,\"memtables\":[{\"generation\":8,\"rows\":5,"
             + "\"bytes\":64,\"batches\":2,\"indexes\":[\"id_idx\"]}]}]}}");
 
-    BucketStats decoded = lsm.getLsmStats(true).get().buckets().get(0);
+    TableShardStats decoded = lsm.getLsmStats(true).get().tableShards().get(0);
 
     assertEquals(3, decoded.replayAfterWalEntryPosition());
     assertEquals(11, decoded.walEntryPositionLastSeen());
     assertTrue(decoded.compacting());
-    assertEquals(42, decoded.generations().get(0).rows().getAsLong());
+    assertEquals(42, decoded.sstables().get(0).rows().getAsLong());
     assertTrue(decoded.memtables().isPresent());
     MemtableStats memtable = decoded.memtables().get().get(0);
     assertEquals(8, memtable.generation());
@@ -289,7 +289,7 @@ public class LanceDbTableLsmTest {
 
     lsm.getLsmStats();
 
-    assertFalse(MAPPER.readTree(requestBodies.get(0)).get("include_generation_rows").asBoolean());
+    assertFalse(MAPPER.readTree(requestBodies.get(0)).get("include_sstable_rows").asBoolean());
   }
 
   // ===========================================================================
@@ -334,8 +334,8 @@ public class LanceDbTableLsmTest {
   @Test
   public void testCheckpointReturnsWhenNoGenerationsOutstanding() {
     enqueue("flush_lsm", 200, "");
-    // A bucket with no L0 generations yields no target, so the drain never starts.
-    enqueue("get_lsm_stats", 200, stats(bucket("shard-0", false)));
+    // A table shard with no SSTables yields no target, so the drain never starts.
+    enqueue("get_lsm_stats", 200, stats(tableShard("shard-0", false)));
 
     lsm.checkpointLsm();
 
@@ -345,12 +345,12 @@ public class LanceDbTableLsmTest {
   @Test
   public void testCheckpointConvergesOnceTargetGenerationsAreGone() {
     enqueue("flush_lsm", 200, "");
-    // Watermark read: shard-0 holds generations 7 and 8, so target = 8.
-    enqueue("get_lsm_stats", 200, stats(bucket("shard-0", false, 7L, 8L)));
+    // Watermark read: shard-0 holds sstables 7 and 8, so target = 8.
+    enqueue("get_lsm_stats", 200, stats(tableShard("shard-0", false, 7L, 8L)));
     // First drain poll: both still outstanding, nothing compacting -> dispatch a pass.
-    enqueue("get_lsm_stats", 200, stats(bucket("shard-0", false, 7L, 8L)));
+    enqueue("get_lsm_stats", 200, stats(tableShard("shard-0", false, 7L, 8L)));
     // Second drain poll: drained past the target -> done.
-    enqueue("get_lsm_stats", 200, stats(bucket("shard-0", false, 9L)));
+    enqueue("get_lsm_stats", 200, stats(tableShard("shard-0", false, 9L)));
     enqueue("compact_lsm", 200, "");
 
     lsm.checkpointLsm();
@@ -362,14 +362,14 @@ public class LanceDbTableLsmTest {
   @Test
   public void testCheckpointDoesNotPileOnWhileEveryTargetBucketIsCompacting() {
     enqueue("flush_lsm", 200, "");
-    enqueue("get_lsm_stats", 200, stats(bucket("shard-0", true, 4L)));
+    enqueue("get_lsm_stats", 200, stats(tableShard("shard-0", true, 4L)));
     // Still compacting on the first poll, so no pass is dispatched; then it drains.
-    enqueue("get_lsm_stats", 200, stats(bucket("shard-0", true, 4L)));
-    enqueue("get_lsm_stats", 200, stats(bucket("shard-0", false, 5L)));
+    enqueue("get_lsm_stats", 200, stats(tableShard("shard-0", true, 4L)));
+    enqueue("get_lsm_stats", 200, stats(tableShard("shard-0", false, 5L)));
 
     lsm.checkpointLsm();
 
-    assertEquals(0, countCalls("compact_lsm"), "a latched bucket is left alone");
+    assertEquals(0, countCalls("compact_lsm"), "a latched tableShard is left alone");
   }
 
   @Test
@@ -378,7 +378,7 @@ public class LanceDbTableLsmTest {
     // from flush rather than retrying the read in place.
     enqueue("flush_lsm", 200, "");
     enqueue("get_lsm_stats", 421, "no claim");
-    enqueue("get_lsm_stats", 200, stats(bucket("shard-0", false)));
+    enqueue("get_lsm_stats", 200, stats(tableShard("shard-0", false)));
 
     lsm.checkpointLsm();
 
@@ -389,7 +389,7 @@ public class LanceDbTableLsmTest {
   public void testCheckpointRetriesRetryableStatusInPlace() {
     enqueue("flush_lsm", 429, "latch held");
     enqueue("flush_lsm", 200, "");
-    enqueue("get_lsm_stats", 200, stats(bucket("shard-0", false)));
+    enqueue("get_lsm_stats", 200, stats(tableShard("shard-0", false)));
 
     lsm.checkpointLsm();
 
@@ -421,27 +421,27 @@ public class LanceDbTableLsmTest {
 
   /**
    * A stats payload that does not decode must fail closed. Every one of these bodies used to be
-   * read as "no buckets", which is indistinguishable from a drained table, so {@code checkpointLsm}
+   * read as "no tableShards", which is indistinguishable from a drained table, so {@code checkpointLsm}
    * reported convergence for a checkpoint that never ran.
    */
   @Test
   public void testCheckpointRejectsMalformedStats() {
     Map<String, String> malformed = new LinkedHashMap<String, String>();
     malformed.put("no response body at all", "");
-    malformed.put("stats object with no buckets", "{\"lsm_stats\":{}}");
-    malformed.put("bucket missing its required fields", "{\"lsm_stats\":{\"buckets\":[{}]}}");
+    malformed.put("stats object with no tableShards", "{\"lsm_stats\":{}}");
+    malformed.put("tableShard missing its required fields", "{\"lsm_stats\":{\"tableShards\":[{}]}}");
     malformed.put(
-        "bucket missing generations",
-        "{\"lsm_stats\":{\"buckets\":[{\"shard_id\":\"shard-0\",\"status\":\"Active\","
+        "tableShard missing sstables",
+        "{\"lsm_stats\":{\"tableShards\":[{\"shard_id\":\"shard-0\",\"status\":\"Active\","
             + "\"writer_epoch\":1,\"manifest_version\":2,\"current_generation\":9,"
             + "\"replay_after_wal_entry_position\":0,\"wal_entry_position_last_seen\":0,"
             + "\"compacting\":false}]}}");
     malformed.put(
         "generation with a non-numeric generation number",
-        "{\"lsm_stats\":{\"buckets\":[{\"shard_id\":\"shard-0\",\"status\":\"Active\","
+        "{\"lsm_stats\":{\"tableShards\":[{\"shard_id\":\"shard-0\",\"status\":\"Active\","
             + "\"writer_epoch\":1,\"manifest_version\":2,\"current_generation\":9,"
             + "\"replay_after_wal_entry_position\":0,\"wal_entry_position_last_seen\":0,"
-            + "\"generations\":[{\"generation\":\"7\",\"bytes\":1024}],"
+            + "\"sstables\":[{\"generation\":\"7\",\"bytes\":1024}],"
             + "\"compacting\":false}]}}");
 
     for (Map.Entry<String, String> each : malformed.entrySet()) {
@@ -492,22 +492,22 @@ public class LanceDbTableLsmTest {
   // harness
   // ===========================================================================
 
-  private static List<Long> generationNumbers(BucketStats bucket) {
+  private static List<Long> generationNumbers(TableShardStats tableShard) {
     List<Long> numbers = new ArrayList<Long>();
-    for (GenerationStats generation : bucket.generations()) {
+    for (SsTableStats generation : tableShard.sstables()) {
       numbers.add(generation.generation());
     }
     return numbers;
   }
 
-  /** Build an {@code lsm_stats} response body from bucket fragments. */
-  private static String stats(String... buckets) {
-    return "{\"lsm_stats\":{\"buckets\":[" + String.join(",", buckets) + "]}}";
+  /** Build an {@code lsm_stats} response body from tableShard fragments. */
+  private static String stats(String... tableShards) {
+    return "{\"lsm_stats\":{\"tableShards\":[" + String.join(",", tableShards) + "]}}";
   }
 
-  private static String bucket(String shardId, boolean compacting, Long... generations) {
+  private static String tableShard(String shardId, boolean compacting, Long... sstables) {
     StringBuilder gens = new StringBuilder();
-    for (Long generation : generations) {
+    for (Long generation : sstables) {
       if (gens.length() > 0) {
         gens.append(",");
       }
@@ -517,7 +517,7 @@ public class LanceDbTableLsmTest {
         + shardId
         + "\",\"status\":\"Active\",\"writer_epoch\":1,\"manifest_version\":2,"
         + "\"current_generation\":9,\"replay_after_wal_entry_position\":0,"
-        + "\"wal_entry_position_last_seen\":0,\"generations\":["
+        + "\"wal_entry_position_last_seen\":0,\"sstables\":["
         + gens
         + "],\"compacting\":"
         + compacting