Refactor embedding batch_size (#3825)

### What problem does this PR solve?

Refactor embedding batch_size. Close #3657

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)
- [x] Refactoring

rag/benchmark.py

@@ -63,16 +63,13 @@ class Benchmark:
                 run[query][c["chunk_id"]] = c["similarity"]
         return run
 
-    def embedding(self, docs, batch_size=16):
-        vects = []
-        cnts = [d["content_with_weight"] for d in docs]
-        for i in range(0, len(cnts), batch_size):
-            vts, c = self.embd_mdl.encode(cnts[i: i + batch_size])
-            vects.extend(vts.tolist())
-        assert len(docs) == len(vects)
+    def embedding(self, docs):
+        texts = [d["content_with_weight"] for d in docs]
+        embeddings, _ = self.embd_mdl.encode(texts)
+        assert len(docs) == len(embeddings)
         vector_size = 0
         for i, d in enumerate(docs):
-            v = vects[i]
+            v = embeddings[i]
             vector_size = len(v)
             d["q_%d_vec" % len(v)] = v
         return docs, vector_size