- flattened row image is WO_WAL_UPDATE, not WO_WAL_INSERT: the row's
original INSERT is already in a live log, so a second one for the same
id is a duplicate replay refuses as corruption. INSERT is right only
for compaction, which builds a fresh log
- remove WO_CKPT_MAX_GARBAGE: with the absolute term at 64 MiB, garbage
large enough to reach a 256 MiB ceiling has already tripped it, so the
branch was unreachable. Postgres needs both constants because it
thresholds on tuples with its pair at opposite ends; this thresholds
on bytes, where one constant does both jobs
- test_delta_chain_flattens_at_k: chain depth stays <= WO_DELTA_MAX_HOPS
across 2K+2 updates, and a reset is observed
- test_delta_chain_flatten_replays: a flattened chain replays correctly
- test_keys_resident_indexed_across_flatten: a delta on an indexed
column composes with flattening, checked at every step across the
bound and after restart. Found no product defect
- test_should_compact_absolute_and_ceiling: pins the absolute term, the
boundary just under it, and the small-log case the ratio still governs
- test_wal 5700 pass / 0 fail; wovm-test and woc-test green
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
(cherry picked from commit f93b5d9db753305c297e868d977670e6d703684c)
- fixes a limitation iteration 2 shipped: compaction was supposed to
bound chain length, but wo_wal_should_compact triggers on a whole-log
byte ratio and cannot see one hot row's chain
- tier 1, flatten on update: the update path ALREADY folds the row for
index maintenance and the fold already walks hop by hop, so it reports
depth for free. Past a fixed K it writes a full row instead of a
delta. Read <= K+1 reads, replay O(K^2) per row. No format change, no
per-row RAM, no new trigger
- tier 2: our compaction policy has a proportional term and a
SUPPRESSOR misleadingly called a floor; postgres's floor TRIGGERS on
small absolute garbage. Add that term and a ceiling
- design read from .dev/reference/postgresql, not recalled:
heap_page_prune_opt gates on an O(1) on-page hint then page fullness
against Max(fillfactor, BLCKSZ/10); autovacuum uses base + scale *
reltuples clamped by a max (50, 0.2, 1e8). Neither thresholds on
new-bytes-versus-old-bytes
- K deliberately does NOT scale with table size: postgres scales a
table-level aggregate with proportional harm, ours is per-row with
additive cost, so scaling up would make big databases boot worst
- the story says plainly it should NOT be next: task 7 has still never
measured whether resident: keys beats the kernel's own paging
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
(cherry picked from commit f667cad2cfbe187b5973440ab1af015b2df288f8)
