feat: sort input for SentenceTransformerEmbed to save padding cost (#1245)

Author: georgeh0

python/cocoindex/functions/sbert.py

@@ -1,7 +1,6 @@
 """SentenceTransformer embedding functionality."""
 
-import dataclasses
-from typing import Any, Literal
+from typing import Any, Literal, cast
 
 import numpy as np
 from numpy.typing import NDArray
@@ -60,7 +59,18 @@ def analyze(self) -> type:
 
     def __call__(self, text: list[str]) -> list[NDArray[np.float32]]:
         assert self._model is not None
+
+        # Sort the text by length to minimize the number of padding tokens.
+        text_with_idx = [(idx, t) for idx, t in enumerate(text)]
+        text_with_idx.sort(key=lambda x: len(x[1]))
+
         results: list[NDArray[np.float32]] = self._model.encode(
-            text, convert_to_numpy=True
+            [t for _, t in text_with_idx], convert_to_numpy=True
         )
-        return results
+        final_results: list[NDArray[np.float32] | None] = [
+            None for _ in range(len(text))
+        ]
+        for (idx, _), result in zip(text_with_idx, results):
+            final_results[idx] = result
+
+        return cast(list[NDArray[np.float32]], final_results)