refactor: simplify variable pool key structure and improve type safety (#23732)

Signed-off-by: -LAN- <laipz8200@outlook.com>

api/services/workflow_draft_variable_service.py

@@ -13,7 +13,7 @@ from sqlalchemy.sql.expression import and_, or_
 from core.app.entities.app_invoke_entities import InvokeFrom
 from core.file.models import File
 from core.variables import Segment, StringSegment, Variable
-from core.variables.consts import MIN_SELECTORS_LENGTH
+from core.variables.consts import SELECTORS_LENGTH
 from core.variables.segments import ArrayFileSegment, FileSegment
 from core.variables.types import SegmentType
 from core.workflow.constants import CONVERSATION_VARIABLE_NODE_ID, ENVIRONMENT_VARIABLE_NODE_ID, SYSTEM_VARIABLE_NODE_ID
@@ -147,7 +147,7 @@ class WorkflowDraftVariableService:
     ) -> list[WorkflowDraftVariable]:
         ors = []
         for selector in selectors:
-            assert len(selector) >= MIN_SELECTORS_LENGTH, f"Invalid selector to get: {selector}"
+            assert len(selector) >= SELECTORS_LENGTH, f"Invalid selector to get: {selector}"
             node_id, name = selector[:2]
             ors.append(and_(WorkflowDraftVariable.node_id == node_id, WorkflowDraftVariable.name == name))
 
@@ -608,7 +608,7 @@ class DraftVariableSaver:
 
         for item in updated_variables:
             selector = item.selector
-            if len(selector) < MIN_SELECTORS_LENGTH:
+            if len(selector) < SELECTORS_LENGTH:
                 raise Exception("selector too short")
             # NOTE(QuantumGhost): only the following two kinds of variable could be updated by
             # VariableAssigner: ConversationVariable and iteration variable.