chore: drain large digest and prune backlogs in small batches

[MicBun]

Digest had never run on testnet, so enabling it queued 16 years of history at once.
That is far larger than any backlog the current batch sizing was chosen against, and
at that size one firing asks for more work than a single block can commit. Five
consecutive firings, no days drained:

09-05 00:02:53Z   09-05 06:00:40Z   09-05 12:00:39Z
09-05 18:00:41Z   09-06 00:00:42Z

Each ends the same way:

node stopped with error: error proposing block: error executing the block:
failed to precommit block transaction: precommit timed out waiting for
commit ID from replication monitor

Where the limit comes from

kwild issues PREPARE TRANSACTION, then waits for Postgres logical replication to
decode that block's whole change set and return a commit ID. That wait is a hardcoded
30 seconds in kwil-db (node/pg/db.go). Past it the node exits, and since the block
never commits, the next firing asks for the same work again.

The scheduler passed DigestDeleteCap = 100_000. auto_digest turns that into a day
count as floor((delete_cap * 3) / (expected_records_per_stream * 2)), so it was
asking for 6,250 days of history in a single transaction. Runs that did commit
were changing around 43,000 rows. Larger ones did not fit the window.

Change

DigestDeleteCap drops to 10,000, which is the default auto_digest itself declares.
A run then covers 625 days and changes at most about 11,000 rows. A backlog simply
takes more runs, and DrainMaxRuns already allows 100 per firing, which still clears
62,500 days.

PruneDeleteCap drops to 10,000 on the same reasoning. The pruner is the heavier of
the two: it deletes from primitive_events and from primitive_event_type in one
transaction, so an equal cap produces a larger change set than digest's. Its first
mainnet sweep will be a one-time backlog of the same shape as this one.

Both are one-line constant changes. The reasoning sits in the file so the next person
who wants to raise them knows what they are trading against.

Testing

go test -tags kwiltest ./extensions/tn_digest/... passes. Neither constant was
asserted by any test.

Out of scope

The 30-second window is hardcoded upstream and stays that way here. Making it
configurable is a kwil-db change and a separate argument.

Testnet needs digest switched off until this ships in a release.

Context, not closed by this PR:

• resolves Goal: Duplicate record pruning #1414

[holdex]

Time Submission Status

Member	#	Time	Running Total	Status	Last Update
MicBun			4h	✅ Submitted	Sep 7, 2026, 3:18 PM

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• extensions/tn_digest/scheduler/constants.go

📝 Walkthrough

Walkthrough

The scheduler reduces DigestDeleteCap and PruneDeleteCap from 100,000 to 10,000. Comments document the PostgreSQL replication window, day-count calculation, and transaction-size rationale.

Changes

Digest deletion cap adjustment

Layer / File(s)	Summary
Update deletion caps and rationale extensions/tn_digest/scheduler/constants.go	Both deletion caps are set to 10,000. Comments document the replication window and transaction-size calculations.

Estimated code review effort: 1 (Trivial) | ~3 minutes

Merge Risk: 🟡 Moderate · up to a48da

Duplicate pruning may still create an oversized transaction when processing an initial backlog, potentially causing replication timeout failures and retries. Bound the total prune change set or size the cap from measured worst-case data before enabling pruning.

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✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 1…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
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Title check	✅ Passed	The title accurately summarizes the main change: reducing digest and prune deletion caps so large backlogs drain in smaller batches.

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Actionable comments posted: 1

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Inline comments:
In `@extensions/tn_digest/scheduler/constants.go`:
- Line 74: Replace the fixed PruneDeleteCap event-time limit with a bound that
constrains the total rows changed by batch_prune_duplicates, accounting for all
revisions and primitive_event_type markers selected per batch. Derive the cap
from measured worst-case data or enforce a total change-set limit so pruning
stays within the intended replication threshold before enabling it.

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• extensions/tn_digest/scheduler/constants.go

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[MicBun]

@holdex pr submit-time 4h