Currently, when we update the lookaside table in __wt_update_las, we use auto-commit transactions on a special session. This means that new transaction IDs are allocated for lookaside writes and that they are in the future of all other updates in the cache.

However, we want to be able to evict lookaside pages immediately, because we only write to lookaside when the cache is already under pressure. To do this, we have special visibility rules and checks in eviction for lookaside pages.

Instead, we should investigate whether we can use a special transaction ID for lookaside updates (e.g., set to WT_TXN_NONE at commit time) to remove complexity from reconciliation and eviction.