docs(node): clarify full-text search filtering

<!-- lance-gatekeeper-fix:v1 agent=5c80c44c083b3b8ad0da595419d468fc
generation=1 -->

## Root cause

The legacy synchronous Python table called `delete` on a shared, mutable
`lance.Dataset`. Concurrent table operations could hold a PyO3 borrow
while delete requested an exclusive borrow, producing `RuntimeError:
Already borrowed`. The current async-backed binding fixes this by
cloning its thread-safe Rust table handle before awaiting, but that
concurrency contract had no regression coverage.

## Fix

- Document why delete must clone the Rust table handle before entering
its async future.
- Add a barrier-synchronized regression test that deletes distinct rows
through one shared table from eight Python threads.
- Verify every delete commits exactly one row, every commit gets a
distinct version, and no rows remain.

## Validation

- `cargo check --quiet --features remote --tests --examples`
- `cargo fmt --all -- --check`
- `uv run --extra tests --extra dev ruff format --check
python/tests/test_table.py`
- `uv run --extra tests --extra dev ruff check
python/tests/test_table.py`
- `uv run --extra tests --extra dev pytest
python/tests/test_table.py::test_concurrent_deletes_are_thread_safe
python/tests/test_table.py::test_delete
python/tests/test_table.py::test_delete_expr
python/tests/test_table.py::test_delete_expr_async -q` (4 passed)
- Manual stress reproduction: 100 concurrent deletes on one table
completed at versions 2–101 with zero rows remaining.

Fixes #530

Co-authored-by: Gatefixer <313497061+lancedb-gatefixer[bot]@users.noreply.github.com>

docs/src/js/classes/Query.md

@@ -541,7 +541,17 @@ where(predicate): this
 
 A filter statement to be applied to this query.
 
-The filter should be supplied as an SQL query string.  For example:
+Filters are applied before full-text and vector searches by default; no
+separate prefilter call is needed. For vector searches only, use
+[VectorQuery#postfilter](VectorQuery.md#postfilter) to apply the filter after the search.
+
+The filter should be supplied as an SQL query string.
+
+Filtering performance can often be improved by creating a scalar index
+on the filter column(s).
+
+Calling this multiple times combines the filters with a logical AND rather
+than replacing the previous filter.
 
 #### Parameters
 
@@ -551,18 +561,20 @@ The filter should be supplied as an SQL query string.  For example:
 
 `this`
 
-#### Example
+#### Examples
 
 ```ts
-x > 10
-y > 0 AND y < 100
-x > 5 OR y = 'test'
+const results = await table
+  .search("puppy", "fts")
+  .where("meta = 'foo'")
+  .limit(10)
+  .toArray();
+```
 
-Filtering performance can often be improved by creating a scalar index
-on the filter column(s).
-
-Calling this multiple times combines the filters with a logical AND rather
-than replacing the previous filter.
+```ts
+query.where("x > 10");
+query.where("y > 0 AND y < 100");
+query.where("x > 5 OR y = 'test'");
 ```
 
 #### Inherited from

docs/src/js/classes/VectorQuery.md

@@ -560,6 +560,9 @@ postfilter(): VectorQuery
 If this is called then filtering will happen after the vector search instead of
 before.
 
+This method is only available for vector search queries. Full-text search
+filters are always applied before the search.
+
 By default filtering will be performed before the vector search.  This is how
 filtering is typically understood to work.  This prefilter step does add some
 additional latency.  Creating a scalar index on the filter column(s) can
@@ -790,7 +793,17 @@ where(predicate): this
 
 A filter statement to be applied to this query.
 
-The filter should be supplied as an SQL query string.  For example:
+Filters are applied before full-text and vector searches by default; no
+separate prefilter call is needed. For vector searches only, use
+[VectorQuery#postfilter](VectorQuery.md#postfilter) to apply the filter after the search.
+
+The filter should be supplied as an SQL query string.
+
+Filtering performance can often be improved by creating a scalar index
+on the filter column(s).
+
+Calling this multiple times combines the filters with a logical AND rather
+than replacing the previous filter.
 
 #### Parameters
 
@@ -800,18 +813,20 @@ The filter should be supplied as an SQL query string.  For example:
 
 `this`
 
-#### Example
+#### Examples
 
 ```ts
-x > 10
-y > 0 AND y < 100
-x > 5 OR y = 'test'
+const results = await table
+  .search("puppy", "fts")
+  .where("meta = 'foo'")
+  .limit(10)
+  .toArray();
+```
 
-Filtering performance can often be improved by creating a scalar index
-on the filter column(s).
-
-Calling this multiple times combines the filters with a logical AND rather
-than replacing the previous filter.
+```ts
+query.where("x > 10");
+query.where("y > 0 AND y < 100");
+query.where("x > 5 OR y = 'test'");
 ```
 
 #### Inherited from

nodejs/examples/filtering.test.ts

@@ -47,5 +47,22 @@ test("filtering examples", async () => {
       .limit(5)
       .toArray();
     // --8<-- [end:orderby_search]
+
+    const ftsTable = await db.createTable("myFts", [
+      { text: "Frodo was a happy puppy", category: "pet" },
+      { text: "A puppy training guide", category: "guide" },
+      { text: "There are several kittens playing", category: "pet" },
+    ]);
+    await ftsTable.createIndex("text", { config: lancedb.Index.fts() });
+
+    // --8<-- [start:fts_prefilter]
+    const ftsResults = await ftsTable
+      .search("puppy", "fts")
+      .where("category = 'pet'")
+      .limit(10)
+      .toArray();
+    // --8<-- [end:fts_prefilter]
+    expect(ftsResults).toHaveLength(1);
+    expect(ftsResults[0].category).toBe("pet");
   });
 });

nodejs/lancedb/query.ts

@@ -363,17 +363,33 @@ export class StandardQueryBase<
   /**
    * A filter statement to be applied to this query.
    *
-   * The filter should be supplied as an SQL query string.  For example:
-   * @example
-   * x > 10
-   * y > 0 AND y < 100
-   * x > 5 OR y = 'test'
+   * Filters are applied before full-text and vector searches by default; no
+   * separate prefilter call is needed. For vector searches only, use
+   * {@link VectorQuery#postfilter} to apply the filter after the search.
+   *
+   * The filter should be supplied as an SQL query string.
    *
    * Filtering performance can often be improved by creating a scalar index
    * on the filter column(s).
    *
    * Calling this multiple times combines the filters with a logical AND rather
    * than replacing the previous filter.
+   *
+   * @example Filter a full-text search
+   * ```ts
+   * const results = await table
+   *   .search("puppy", "fts")
+   *   .where("meta = 'foo'")
+   *   .limit(10)
+   *   .toArray();
+   * ```
+   *
+   * @example SQL filter expressions
+   * ```ts
+   * query.where("x > 10");
+   * query.where("y > 0 AND y < 100");
+   * query.where("x > 5 OR y = 'test'");
+   * ```
    */
   where(predicate: string): this {
     this.doCall((inner: NativeQueryType) => inner.onlyIf(predicate));
@@ -669,6 +685,9 @@ export class VectorQuery extends StandardQueryBase<NativeVectorQuery> {
    * If this is called then filtering will happen after the vector search instead of
    * before.
    *
+   * This method is only available for vector search queries. Full-text search
+   * filters are always applied before the search.
+   *
    * By default filtering will be performed before the vector search.  This is how
    * filtering is typically understood to work.  This prefilter step does add some
    * additional latency.  Creating a scalar index on the filter column(s) can

python/python/lancedb/db.py

@@ -707,6 +707,9 @@ class LanceDBConnection(DBConnection):
         self._namespace_client_properties = namespace_client_properties
         if _inner is not None:
             self._conn = _inner
+            # Native-derived wrappers resolve this in their async reconstruction
+            # path so construction never synchronously re-enters LOOP.
+            self._read_consistency_interval = read_consistency_interval
             self._cached_namespace_client = None
             return
 
@@ -756,11 +759,14 @@ class LanceDBConnection(DBConnection):
         # storage_options.  Also, this class really shouldn't be holding any state
         # beyond _conn.
         self._conn = AsyncConnection(LOOP.run(do_connect()))
+        # Keep property access synchronous so debugger introspection cannot wait on
+        # the background loop while that thread is suspended at a breakpoint.
+        self._read_consistency_interval = read_consistency_interval
         self._cached_namespace_client: Optional[LanceNamespace] = None
 
     @property
     def read_consistency_interval(self) -> Optional[timedelta]:
-        return LOOP.run(self._conn.get_read_consistency_interval())
+        return self._read_consistency_interval
 
     @property
     def session(self) -> Optional[Session]:
@@ -771,8 +777,16 @@ class LanceDBConnection(DBConnection):
         return self._conn.uri
 
     @classmethod
-    def from_inner(cls, inner: LanceDbConnection):
-        return cls(None, _inner=inner)
+    def from_inner(
+        cls,
+        inner: LanceDbConnection,
+        read_consistency_interval: Optional[timedelta],
+    ):
+        return cls(
+            None,
+            read_consistency_interval=read_consistency_interval,
+            _inner=inner,
+        )
 
     def __repr__(self) -> str:
         return f"{self.__class__.__name__}(uri={self._conn.uri!r})"

python/python/lancedb/permutation.py

@@ -226,7 +226,7 @@ class PermutationBuilder:
 
         async def do_execute():
             inner_tbl = await self._async.execute()
-            return LanceTable.from_inner(inner_tbl)
+            return await LanceTable.from_inner(inner_tbl)
 
         return LOOP.run(do_execute())
 

python/python/lancedb/table.py

@@ -2182,11 +2182,15 @@ class LanceTable(Table):
         return self.name
 
     @classmethod
-    def from_inner(cls, tbl: LanceDBTable):
-        from .db import LanceDBConnection
+    async def from_inner(cls, tbl: LanceDBTable):
+        from .db import AsyncConnection, LanceDBConnection
 
         async_tbl = AsyncTable(tbl)
-        conn = LanceDBConnection.from_inner(tbl.database())
+        inner_conn = tbl.database()
+        read_consistency_interval = await AsyncConnection(
+            inner_conn
+        ).get_read_consistency_interval()
+        conn = LanceDBConnection.from_inner(inner_conn, read_consistency_interval)
         return cls(
             conn,
             async_tbl.name,

python/python/tests/test_db.py

@@ -77,6 +77,23 @@ def test_sync_repr_does_not_use_background_loop(tmp_path, monkeypatch):
     assert repr(table) == f"LanceTable(name='test', _conn={db!r})"
 
 
+def test_read_consistency_interval_does_not_use_background_loop(tmp_path, monkeypatch):
+    from lancedb.background_loop import LOOP
+    from lancedb.db import LanceDBConnection
+
+    consistency_interval = timedelta(seconds=5)
+    db = lancedb.connect(tmp_path, read_consistency_interval=consistency_interval)
+    db_from_inner = LanceDBConnection.from_inner(db._inner, consistency_interval)
+
+    def fail_run(*args, **kwargs):
+        raise AssertionError("properties should not use the Python background loop")
+
+    monkeypatch.setattr(LOOP, "run", fail_run)
+
+    assert db.read_consistency_interval == consistency_interval
+    assert db_from_inner.read_consistency_interval == consistency_interval
+
+
 def test_ingest_pd(tmp_path):
     db = lancedb.connect(tmp_path)
 

python/python/tests/test_permutation.py

@@ -6,6 +6,7 @@ import math
 import pytest
 
 from lancedb import DBConnection, Table, connect
+from lancedb.background_loop import LOOP
 from lancedb.permutation import Permutation, Permutations, permutation_builder
 
 
@@ -31,6 +32,25 @@ def test_split_random_ratios(mem_db):
     assert 65 <= split_1_count <= 75  # ~70% ± tolerance
 
 
+def test_execute_does_not_reenter_background_loop(tmp_path, monkeypatch):
+    import threading
+
+    db = connect(tmp_path)
+    tbl = db.create_table("test_table", pa.table({"x": range(10)}))
+    original_run = LOOP.run
+
+    def fail_on_reentry(future):
+        assert threading.current_thread() is not LOOP.thread
+        return original_run(future)
+
+    monkeypatch.setattr(LOOP, "run", fail_on_reentry)
+
+    permutation_tbl = permutation_builder(tbl).execute()
+
+    assert permutation_tbl.count_rows() == 10
+    assert permutation_tbl._conn.read_consistency_interval is None
+
+
 def test_split_random_counts(mem_db):
     """Test random splitting with absolute counts."""
     tbl = mem_db.create_table(

python/python/tests/test_table.py

@@ -6,6 +6,7 @@ import os
 import sys
 import threading
 import warnings
+from concurrent.futures import ThreadPoolExecutor
 from datetime import date, datetime, timedelta
 from time import sleep
 from typing import List
@@ -2124,6 +2125,27 @@ def test_delete(mem_db: DBConnection):
     assert table.to_arrow()["id"].to_pylist() == [1]
 
 
+def test_concurrent_deletes_are_thread_safe(mem_db: DBConnection):
+    num_workers = 8
+    table = mem_db.create_table(
+        "my_table", data=[{"id": row_id} for row_id in range(num_workers)]
+    )
+    barrier = threading.Barrier(num_workers)
+
+    def delete(row_id: int):
+        barrier.wait()
+        return table.delete(f"id = {row_id}")
+
+    with ThreadPoolExecutor(max_workers=num_workers) as pool:
+        results = list(pool.map(delete, range(num_workers)))
+
+    assert all(result.num_deleted_rows == 1 for result in results)
+    assert sorted(result.version for result in results) == list(
+        range(2, num_workers + 2)
+    )
+    assert table.count_rows() == 0
+
+
 def test_delete_expr(mem_db: DBConnection):
     table = mem_db.create_table(
         "my_table",

python/src/table.rs

@@ -745,6 +745,9 @@ impl Table {
 
     #[allow(private_interfaces)]
     pub fn delete(self_: PyRef<'_, Self>, condition: PredicateArg) -> PyResult<Bound<'_, PyAny>> {
+        // Do not hold the Python borrow across the await.  The cloned Rust table
+        // handle is thread-safe and allows deletes on the same Python table to
+        // run concurrently without PyO3 reporting "Already borrowed".
         let inner = self_.inner_ref()?.clone();
         future_into_py(self_.py(), async move {
             let result = match &condition {