Feat: add meta data filter. (#9405)

### What problem does this PR solve?

#8531 
#7417 
#6761 
#6573
#6477

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

api/db/services/document_service.py

@@ -574,6 +574,25 @@ class DocumentService(CommonService):
     def update_meta_fields(cls, doc_id, meta_fields):
         return cls.update_by_id(doc_id, {"meta_fields": meta_fields})
 
+    @classmethod
+    @DB.connection_context()
+    def get_meta_by_kbs(cls, kb_ids):
+        fields = [
+            cls.model.id,
+            cls.model.meta_fields,
+        ]
+        meta = {}
+        for r in cls.model.select(*fields).where(cls.model.kb_id.in_(kb_ids)):
+            doc_id = r.id
+            for k,v in r.meta_fields.items():
+                if k not in meta:
+                    meta[k] = {}
+                v = str(v)
+                if v not in meta[k]:
+                    meta[k][v] = []
+                meta[k][v].append(doc_id)
+        return meta
+
     @classmethod
     @DB.connection_context()
     def update_progress(cls):