Feat/add retriever rerank (#1560)

Co-authored-by: jyong <jyong@dify.ai>

api/models/dataset.py

@@ -3,7 +3,7 @@ import pickle
 from json import JSONDecodeError
 
 from sqlalchemy import func
-from sqlalchemy.dialects.postgresql import UUID
+from sqlalchemy.dialects.postgresql import UUID, JSONB
 
 from extensions.ext_database import db
 from models.account import Account
@@ -15,6 +15,7 @@ class Dataset(db.Model):
     __table_args__ = (
         db.PrimaryKeyConstraint('id', name='dataset_pkey'),
         db.Index('dataset_tenant_idx', 'tenant_id'),
+        db.Index('retrieval_model_idx', "retrieval_model", postgresql_using='gin')
     )
 
     INDEXING_TECHNIQUE_LIST = ['high_quality', 'economy']
@@ -39,7 +40,7 @@ class Dataset(db.Model):
     embedding_model = db.Column(db.String(255), nullable=True)
     embedding_model_provider = db.Column(db.String(255), nullable=True)
     collection_binding_id = db.Column(UUID, nullable=True)
-
+    retrieval_model = db.Column(JSONB, nullable=True)
 
     @property
     def dataset_keyword_table(self):
@@ -93,6 +94,20 @@ class Dataset(db.Model):
         return Document.query.with_entities(func.coalesce(func.sum(Document.word_count))) \
             .filter(Document.dataset_id == self.id).scalar()
 
+    @property
+    def retrieval_model_dict(self):
+        default_retrieval_model = {
+            'search_method': 'semantic_search',
+            'reranking_enable': False,
+            'reranking_model': {
+                'reranking_provider_name': '',
+                'reranking_model_name': ''
+            },
+            'top_k': 2,
+            'score_threshold_enable': False
+        }
+        return self.retrieval_model if self.retrieval_model else default_retrieval_model
+
 
 class DatasetProcessRule(db.Model):
     __tablename__ = 'dataset_process_rules'
@@ -120,7 +135,7 @@ class DatasetProcessRule(db.Model):
         ],
         'segmentation': {
             'delimiter': '\n',
-            'max_tokens': 1000
+            'max_tokens': 512
         }
     }
 
@@ -462,4 +477,3 @@ class DatasetCollectionBinding(db.Model):
     model_name = db.Column(db.String(40), nullable=False)
     collection_name = db.Column(db.String(64), nullable=False)
     created_at = db.Column(db.DateTime, nullable=False, server_default=db.text('CURRENT_TIMESTAMP(0)'))
-