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Let snapshots with a delta callback installed use the insert route

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A pull request for this has already been merged.

  • #2136 by @justinjoy — merged

Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
25/100
Issue type
Refactor
Clarity
Mostly clear
Activity status
Active
Tech stack
c
Domain
databases

Research direction

Start in col_session_snapshot_impl() and the #1030 guard that sets pending_full_input_eval, then read session_snapshot_insert() and col_session_set_delta_cb to see when the insert route applies. First settle the open question of what a snapshot owes a delta callback, since that decides whether the guard can be dropped or whether head_delta must be sent to the observer. Done means the new tests pass at W=1 and W=4 and tests/test_easy_callback_cleared.c and tests/test_easy_callback_snapshot.c stay green.

Written by the indexing model from the issue text.

Description

enhancement

Summary

With a delta callback installed, a snapshot after an incremental insert still evaluates in full: the #1030 guard in col_session_snapshot_impl() sets pending_full_input_eval when delta_cb != NULL && last_inserted_relation != NULL, and clearing the callback with an insert pending does the same (#2108, col_session_set_delta_cb). Since #2114 the insert route (session_snapshot_insert(), occurrence-bound instances) is correct for monotone, aggregate-free strata, so these guards now only cost speed.

Question to settle first

What a snapshot owes a delta callback. Snapshots publish the model through the snapshot callback; delta events are emitted by steps (col_session_step_impl / col_stratum_step_with_delta). Confirm whether a snapshot with a callback installed must leave the session so the next step reports exactly the changes since the last step, and whether the insert route already satisfies that (the #2114 review probe found a delta-callback step after an insert-route snapshot fired exactly the expected deltas).

Proposed change

  • If the snapshot owes callbacks nothing beyond that, drop the #1030 guard and the #2108 flag for strata the insert route admits, and keep them for the rest.
  • If it must report the insert's changes, return each stratum's head deltas (head_delta from wl_columnar_eval_tdd_insert_stratum(), already untimed private copies) to the delta observer instead of falling back to a full evaluation.
  • Tests: snapshots with a callback installed after incremental inserts (internal API and wl_session_make_compound), followed by steps, compared with a session that never had a callback; and the callback event sequences compared with a full-evaluation session.

Acceptance

  • Correct models and callback sequences in the new tests at W=1 and W=4.
  • tests/test_easy_callback_cleared.c and tests/test_easy_callback_snapshot.c stay green.
Dominant language
C
Stars
18
Forks
2
Avg merge
6h 16m
Merged PRs (30d)
286

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