feat(api): Adjust WorkflowDraftVariable and WorkflowNodeExecutionModel (#20746)

- Add `node_execution_id` column to `WorkflowDraftVariable`, allowing efficient implementation of 
  the "Reset to last run value" feature.
- Add additional index for `WorkflowNodeExecutionModel` to improve the performance of last run lookup.

Closes #20745.

api/migrations/versions/2025_06_06_1424-4474872b0ee6_workflow_draft_varaibles_add_node_execution_id.py

@@ -0,0 +1,60 @@
+"""`workflow_draft_varaibles` add `node_execution_id` column, add an index for `workflow_node_executions`.
+
+Revision ID: 4474872b0ee6
+Revises: 2adcbe1f5dfb
+Create Date: 2025-06-06 14:24:44.213018
+
+"""
+from alembic import op
+import models as models
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '4474872b0ee6'
+down_revision = '2adcbe1f5dfb'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # `CREATE INDEX CONCURRENTLY` cannot run within a transaction, so use the `autocommit_block`
+    # context manager to wrap the index creation statement.
+    # Reference:
+    #
+    # - https://www.postgresql.org/docs/current/sql-createindex.html#:~:text=Another%20difference%20is,CREATE%20INDEX%20CONCURRENTLY%20cannot.
+    # - https://alembic.sqlalchemy.org/en/latest/api/runtime.html#alembic.runtime.migration.MigrationContext.autocommit_block
+    with op.get_context().autocommit_block():
+        op.create_index(
+            op.f('workflow_node_executions_tenant_id_idx'),
+            "workflow_node_executions",
+            ['tenant_id', 'workflow_id', 'node_id', sa.literal_column('created_at DESC')],
+            unique=False,
+            postgresql_concurrently=True,
+        )
+
+    with op.batch_alter_table('workflow_draft_variables', schema=None) as batch_op:
+        batch_op.add_column(sa.Column('node_execution_id', models.types.StringUUID(), nullable=True))
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+
+    # `DROP INDEX CONCURRENTLY` cannot run within a transaction, so use the `autocommit_block`
+    # context manager to wrap the index creation statement.
+    # Reference:
+    #
+    # - https://www.postgresql.org/docs/current/sql-createindex.html#:~:text=Another%20difference%20is,CREATE%20INDEX%20CONCURRENTLY%20cannot.
+    # - https://alembic.sqlalchemy.org/en/latest/api/runtime.html#alembic.runtime.migration.MigrationContext.autocommit_block
+    # `DROP INDEX CONCURRENTLY` cannot run within a transaction, so commit existing transactions first.
+    # Reference:
+    #
+    # https://www.postgresql.org/docs/current/sql-createindex.html#:~:text=Another%20difference%20is,CREATE%20INDEX%20CONCURRENTLY%20cannot.
+    with op.get_context().autocommit_block():
+        op.drop_index(op.f('workflow_node_executions_tenant_id_idx'), postgresql_concurrently=True)
+
+    with op.batch_alter_table('workflow_draft_variables', schema=None) as batch_op:
+        batch_op.drop_column('node_execution_id')
+
+    # ### end Alembic commands ###