"""add source_task_id to fission_tasks

Revision ID: 019
Revises: 018
Create Date: 2026-06-18

裂变补图/重生需复刻首轮上下文(产品+operator key+张数)，故在 fission_tasks
存下源 GenerationTask id。新架构不再扇出 GenerationTask，旧的 source_fission_id
反查链断裂，本列补齐回查能力。
"""
from alembic import op
import sqlalchemy as sa

revision = "019"
down_revision = "018"
branch_labels = None
depends_on = None


def upgrade():
    op.add_column(
        "fission_tasks",
        sa.Column("source_task_id", sa.BigInteger, nullable=True,
                  comment="源 GenerationTask id（补图复刻上下文用）"),
    )


def downgrade():
    op.drop_column("fission_tasks", "source_task_id")