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Backend now tracks last-seq as a monotonic high-water mark (survives truncation) and exposes :truncate-through. compaction.sx: persist/compact checkpoints then drops events with seq <= snapshot seq; should-compact?/ maybe-compact give an explicit every-N policy. Determinism: post-compaction replay value == uncompacted full replay. Phase 3 complete, 76/76. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
44 lines
1.4 KiB
Plaintext
44 lines
1.4 KiB
Plaintext
; persist/log — the log facet: append-only event streams. seq is assigned from
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; a monotonic per-stream high-water mark (1-based) held by the backend, so it
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; keeps climbing even after the log prefix is compacted away. Reads return the
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; events currently stored, oldest-first.
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; Requires: lib/persist/event.sx, lib/persist/backend.sx.
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; logical last seq assigned in a stream (0 if none) — survives compaction
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(define
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persist/last-seq
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(fn (b stream) (persist/backend-last-seq b stream)))
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; number of events physically stored in a stream (shrinks on compaction)
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(define
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persist/count
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(fn (b stream) (len (persist/backend-read b stream))))
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; append an event, auto-assigning the next seq. Returns the stored event.
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(define
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persist/append
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(fn
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(b stream type at data)
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(let
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((seq (+ 1 (persist/last-seq b stream))))
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(let
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((ev (persist/event stream seq type at data)))
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(begin (persist/backend-append b stream ev) ev)))))
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; read all events currently stored in a stream, oldest-first
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(define persist/read (fn (b stream) (persist/backend-read b stream)))
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; read events with seq >= from
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(define
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persist/read-from
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(fn
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(b stream from)
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(filter
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(fn (e) (>= (persist/event-seq e) from))
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(persist/read b stream))))
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; drop events with seq <= n (compaction); the seq counter is untouched
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(define
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persist/truncate
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(fn (b stream n) (persist/backend-truncate b stream n)))
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