refactor(knowledge): keep latest version only

ai_knowledge_base_v2/apps/backend/alembic/versions/0012_knowledge_latest_only.py

@@ -0,0 +1,55 @@
+"""keep only the latest knowledge version
+
+Revision ID: 0012_knowledge_latest_only
+Revises: 0011_knowledge_auto_publish
+"""
+
+from alembic import op
+
+
+revision = "0012_knowledge_latest_only"
+down_revision = "0011_knowledge_auto_publish"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.execute("UPDATE sys_knowledge SET pending_version_id = NULL")
+    for table in (
+        "sys_knowledge_review_record",
+        "sys_knowledge_card",
+        "sys_knowledge_chunk",
+        "sys_knowledge_section",
+        "sys_knowledge_manifest",
+    ):
+        op.execute(
+            f"""
+            DELETE detail
+            FROM {table} AS detail
+            JOIN sys_knowledge AS knowledge ON knowledge.id = detail.knowledge_id
+            WHERE knowledge.current_version_id IS NULL
+               OR detail.version_id <> knowledge.current_version_id
+            """
+        )
+    op.execute(
+        """
+        DELETE version
+        FROM sys_knowledge_version AS version
+        JOIN sys_knowledge AS knowledge ON knowledge.id = version.knowledge_id
+        WHERE knowledge.current_version_id IS NULL
+           OR version.id <> knowledge.current_version_id
+        """
+    )
+    op.execute(
+        """
+        DELETE snapshot
+        FROM sys_knowledge_source_snapshot AS snapshot
+        LEFT JOIN sys_knowledge_version AS version ON version.snapshot_id = snapshot.id
+        WHERE version.id IS NULL
+        """
+    )
+
+
+def downgrade() -> None:
+    # Removed historical content cannot be reconstructed from the latest version.
+    pass