feat: adds isin support to the 'Expr' builder (#3523)

The `Expr` build already includes a lot of useful filtering options,
`eq, ne, gt/gte, lt/lte, and_, or_, contains, cast`, but is was missing
a membership like `isin`. This PR adds that support, as minimally as
possible, allowing easy filtering for membership in a list, without
needing to be a series of `where` expressions.

I didn't see anything in CONTRIBUTING.md about needing a feature request
or issue first, so I just made the change. My apologies if I missed that
somewhere.

Thanks for the vector store, we're using it now in paperless-ngx.

python/python/lancedb/_lancedb.pyi

@@ -48,6 +48,7 @@ class PyExpr:
     def lower(self) -> "PyExpr": ...
     def upper(self) -> "PyExpr": ...
     def contains(self, substr: "PyExpr") -> "PyExpr": ...
+    def isin(self, values: List["PyExpr"]) -> "PyExpr": ...
     def cast(self, data_type: pa.DataType) -> "PyExpr": ...
     def to_sql(self) -> str: ...
 

python/python/lancedb/expr.py

@@ -19,7 +19,7 @@ operators::
 
 from __future__ import annotations
 
-from typing import Union
+from typing import Iterable, Union
 
 import pyarrow as pa
 
@@ -174,6 +174,11 @@ class Expr:
         """Return True where the string contains *substr*."""
         return Expr(self._inner.contains(_coerce(substr)._inner))
 
+    def isin(self, values: "Iterable[ExprLike]") -> "Expr":
+        """Return True where the value is one of *values* (SQL ``IN``)."""
+        inner = [_coerce(v)._inner for v in values]
+        return Expr(self._inner.isin(inner))
+
     # ── type cast ────────────────────────────────────────────────────────────
 
     def cast(self, data_type: Union[str, "pa.DataType"]) -> "Expr":