Migrate column_stats timestamp surfaces to Jiff

[danbi2990]

Background

column_stats currently exposes chrono::NaiveDateTime through public table methods while storing timestamp keys as i64 nanoseconds. Stored values also include structured statistics where structured::Element::DateTime is already Jiff-backed.

This implementation should migrate the public/API and internal conversion surfaces to Jiff while preserving the existing stored key contract.

Prerequisites

• column_stats timestamp contract baseline has landed.
• Any old-format fixture needed by the touched column_stats surface exists before production type changes are made.

Scope

• Migrate public column_stats methods that accept or return chrono::NaiveDateTime.
• Preserve the internal i64 nanoseconds key layout.
• Migrate Statistics.batch_ts as needed.
• Preserve load_rounds_by_cluster seek/pagination behavior.
• Keep structured::Element::DateTime handling compatible with the existing Jiff-backed structured value behavior.

Acceptance criteria

• Existing column_stats baseline fixtures continue to pass.
• The same logical timestamp produces the same stored key bytes.
• Query, seek, pagination, and purge behavior affected by timestamp ordering remain covered by tests.
• Public/API impact is visible in tests or compile checks.
• Any remaining chrono usage in the touched column_stats surface is removed or explicitly justified as compatibility code.

Out of scope

• Event key migration.
• Stored bincode table value migrations outside column_stats.
• Final chrono dependency cleanup.

Notes

Related discussion: #733

[octoaide]

Hi @danbi2990 — checking in on this migration (migrate column_stats timestamp surfaces to Jiff). You assigned yourself two weeks ago but there’s been no activity since; the prerequisites referenced in the issue (baseline tests and pagination fixes) are closed, so there are no remaining blockers listed in the issue. Could you please post a short status update?

Specifically:

• Is work already in progress locally or in a draft PR? If so, could you point me to the branch/PR or summarize the current status?
• Are there any remaining old-format fixtures or other blockers I should be aware of before changing public types?
• Do you want to retain the assignment and complete this yourself, or would you like me to implement the migration (I can open a PR)? If you want me to implement it, please either (a) unassign yourself so I may proceed, or (b) explicitly delegate to me in a comment (e.g. “please proceed”).

If helpful, I can start by proposing a small set of sub-tasks and an implementation plan (change public APIs to Jiff, preserve i64 ns key serialization, migrate Statistics.batch_ts, keep load_rounds_by_cluster seek/pagination behavior, update/verify fixtures and tests), and then open a draft PR. @sophie-cluml @sehkone — pinging for visibility in case you have priorities or constraints for this change.

Please reply with a one-line status or 👍/👎 so we can decide next steps.

[octoaide]

Hi @sophie-cluml and @sehkone — I previously checked in on this migration (migrate column_stats timestamp surfaces to Jiff) when it was assigned to @danbi2990. The issue is now assigned to @sophie-cluml and there hasn’t been activity for a few days. I verified that the prerequisites referenced in the issue (#748 and #760) are closed, so there don’t appear to be remaining blockers listed.

Quick status check please:

• Is work already in progress (local branch or draft PR)? If so, could you point me to the branch/PR or post a short status summary?
• Are there any remaining old-format fixtures or other blockers I should be aware of before changing public types?
• Do you want to retain the assignment and complete this yourself, or would you like me to implement the migration? If you want me to implement it, please either (a) unassign yourself so I may proceed, or (b) explicitly delegate to me in a comment (e.g. “please proceed”).

If helpful I can immediately:

• Propose a small set of sub-tasks and open a draft PR that changes public APIs to Jiff while preserving the i64 ns key serialization, migrates Statistics.batch_ts, maintains load_rounds_by_cluster seek/pagination behavior, and updates tests/fixtures; or
• Open a ready PR and follow up with tests if you unassign or delegate.

Please reply with a one-line status, ETA, or a 👍/👎 and whether you delegate the implementation. Thanks!

[octoaide]

Hi @sophie-cluml and @sehkone — following up on this migration (migrate column_stats timestamp surfaces to Jiff). I previously checked in when the issue was assigned to @danbi2990 and again after it was reassigned; the prerequisites referenced in the issue (#748 and #760) are now closed, so there don’t appear to be remaining blockers listed.

Quick status check / request:

• Is work already in progress locally or in a draft PR? If so, please point me to the branch/PR or post a short status summary.
• Are there any remaining old-format fixtures or other blockers I should be aware of before changing public types?
• Do you want to retain the assignment and complete this yourself, or would you like me to implement the migration? If you want me to implement it, please either (a) unassign yourself so I may proceed, or (b) explicitly delegate to me in a comment (e.g. “please proceed”).

If you delegate or unassign, I can immediately:

1. Open a draft PR that changes public column_stats APIs to use Jiff while preserving the i64 ns key serialization.
2. Migrate Statistics.batch_ts and keep load_rounds_by_cluster seek/pagination behavior.
3. Update and run the baseline fixtures and add tests ensuring the same logical timestamp produces the same stored key bytes and that pagination/seek/purge behavior remains covered.

Please reply with a one-line status, ETA, or 👍/👎 and whether you delegate the implementation. If you prefer to keep the issue, an ETA (even rough) would be helpful so we can plan around it. Thanks!