refactor: port DatasetProcessRule (#31004)

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Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
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api/core/rag/index_processor/processor/parent_child_index_processor.py

@@ -29,6 +29,7 @@ from libs import helper
 from models import Account
 from models.dataset import ChildChunk, Dataset, DatasetProcessRule, DocumentSegment
 from models.dataset import Document as DatasetDocument
+from models.enums import ProcessRuleMode
 from services.account_service import AccountService
 from services.summary_index_service import SummaryIndexService
 
@@ -325,7 +326,7 @@ class ParentChildIndexProcessor(BaseIndexProcessor):
             # update document parent mode
             dataset_process_rule = DatasetProcessRule(
                 dataset_id=dataset.id,
-                mode="hierarchical",
+                mode=ProcessRuleMode.HIERARCHICAL,
                 rules=json.dumps(
                     {
                         "parent_mode": parent_childs.parent_mode,