writeonce/docs/stories/databasev2
shoney.arickathil 2cad84b7c6 feat(db2-chains): bound a keys-resident row's delta chain
TESTS DELIBERATELY HELD at the developer's instruction — logic only.
The existing suite passes (36 suites, 0 fail) but exercises NEITHER new
behaviour: nothing builds a 16-deep chain, and no checkpoint test uses a
log near 64 MiB. Green here means "did not break what existed".

- tier 1: wo_wal_fold_row_at gains hops_out. The walk already visits
  every hop, so the depth is free — this is the design's pd_prune_xid,
  a cheap "is work worth doing" hint taken from work already happening
- the update path branches on it: past WO_DELTA_MAX_HOPS (16) it writes
  a full-row image instead of a delta, terminating the chain. `r`
  already holds the complete post-update row because index maintenance
  required folding it, so flattening costs bytes, not an extra read
- wo_wal_append_row_image encodes from a caller-held row, as
  WO_WAL_INSERT: a chain's base must replay into a database where
  nothing precedes it, so replay/compaction/fold need no change
- tier 2: should_compact gains a TRIGGERING absolute term and a ceiling.
  Our `floor` SUPPRESSES on a small log — the opposite of postgres's
  vac_base_thresh, which triggers on a small absolute problem the
  proportion hides. We had the proportion and the suppressor and
  neither real guard
- verified by construction, not test: both update entry points converge
  on row_apply_field_keys; db.c captures next_offset BEFORE calling in,
  so the re-point is transparent to which record type was written

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
(cherry picked from commit 1b808abd5942de81c3a6416714d1302384103040)
2026-08-30 20:38:03 +02:00
..
00-story.md docs(db2-chains): spec + story for bounding a row's delta chain 2026-08-30 20:38:03 +02:00
01-ram-ceiling-measurement.md feat(db-bench): replay baseline — boot cost tracks history, not data 2026-08-27 21:25:24 +02:00
02-table-storage-modes.md feat(db2-keys): gate the residency measurement, close out task 7 2026-08-30 20:38:03 +02:00
03-wal-checkpoint.md docs(db2-keys): reconcile databasev2 and porch markdown with the code 2026-08-30 20:36:55 +02:00
04-io-uring-commit.md Merge master into db-residency-doctrine — and close the two half-exposed features 2026-08-29 10:14:25 +02:00
05-bounded-tables-eviction.md docs(databasev2): propagate iteration 1's findings to every consumer 2026-08-27 22:47:37 +02:00
06-cold-tiering.md docs(db2-keys): reconcile databasev2 and porch markdown with the code 2026-08-30 20:36:55 +02:00
07-single-file-db.md docs(stories): add readiness, retire status: refine, sweep all 47 iterations 2026-08-27 16:54:45 +02:00
08-query-grammar-corpus.md docs(stories): add readiness, retire status: refine, sweep all 47 iterations 2026-08-27 16:54:45 +02:00
09-cross-program-tables.md docs(stories): add readiness, retire status: refine, sweep all 47 iterations 2026-08-27 16:54:45 +02:00
10-keypair-attach-auth.md docs(stories): add readiness, retire status: refine, sweep all 47 iterations 2026-08-27 16:54:45 +02:00
11-bounded-delta-chains.md feat(db2-chains): bound a keys-resident row's delta chain 2026-08-30 20:38:03 +02:00