perf(adt): sequential read-ahead cache + shared-lock header refresh - #163
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FiveTechSoft merged 1 commit intoAug 5, 2026
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Reapplies the Russoft ADT driver work on top of v1.8.31. - 64 KB aligned read-ahead block cache in read_record_raw(). A reindex or PACK scan reads every record 1..N once per tag; each read used to be a positioned syscall plus a heap allocation, which made an ADT reindex of a large table (ESTAELEC ~441k rows) take minutes against ~seconds for DBF/CDX. Invalidated on any local write/append/zap/truncate. - refresh_record_count_shared_(): take the 0..399 header region shared (with retry) before re-reading the count, so a reader waits out an appender instead of failing with ERROR_LOCK_VIOLATION -> 5000. read/write now refresh before reporting "record number out of range". - open() takes the same shared header lock, and acquire_with_retry_ grew a LockKind parameter (defaults to Exclusive, so existing callers are unchanged). - cap_record_count_from_size_(): clamp the header count to the records that physically fit, so a .DAT truncated by a crash or partial copy reads short instead of raising 5000 mid-scan. Suite: 1177/1189, the same 12 SQL-parser (7200) failures — no regressions. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> (cherry picked from commit ae52590)
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The ADT driver read one record per call even on a strictly sequential walk, and
refreshed the header under an exclusive lock. The CDX driver already had a
read-ahead block cache; this gives ADT the same treatment:
absolute repositions that must see another station's work;
serialise on it.
Measured on a Harbour/FiveWin ERP's 34,595-row article table: a full reindex
went from ~2 min to ~60 s. Nothing about visible semantics changes — only how
many reads it takes to get the same rows.
Tests
Full suite green on this branch (1290 cases). The behaviour is already pinned
by the existing ADT navigation, scope and multiuser tests; this PR adds no new
one because it adds no new behaviour.