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kv.sx: persist/kv-cas sets a key only if its current value equals expected,
else returns {:conflict :expected :actual}; persist/kv-put-new is create-only.
The kv analogue of log append-expect — atomic current-state for sessions, acl
grants, stock counts. 133/133.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
45 lines
1.6 KiB
Plaintext
45 lines
1.6 KiB
Plaintext
; persist/kv — the kv facet: current-state values, no history. For things
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; whose history does NOT matter (stock counts, config, profiles, session
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; blobs) and where projections materialize their read models.
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; Requires: lib/persist/backend.sx.
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(define persist/kv-get (fn (b key) (persist/backend-kv-get b key)))
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(define
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persist/kv-put
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(fn (b key val) (begin (persist/backend-kv-put b key val) val)))
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(define persist/kv-delete (fn (b key) (persist/backend-kv-delete b key)))
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(define persist/kv-has? (fn (b key) (persist/backend-kv-has? b key)))
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(define persist/kv-keys (fn (b) (persist/backend-kv-keys b)))
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; get with a default when the key is absent
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(define
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persist/kv-get-or
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(fn
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(b key dflt)
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(if (persist/kv-has? b key) (persist/kv-get b key) dflt)))
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; read-modify-write: apply f to the current value (or dflt if absent), store result
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(define
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persist/kv-update
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(fn
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(b key dflt f)
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(persist/kv-put b key (f (persist/kv-get-or b key dflt)))))
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; compare-and-swap: set key to new ONLY if its current value equals expected.
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; Returns new on success, or a conflict value {:conflict true :expected :actual}
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; the caller can re-read and retry on. The kv analogue of log append-expect.
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(define
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persist/kv-cas
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(fn
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(b key expected new)
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(let
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((actual (persist/kv-get b key)))
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(if (equal? actual expected) (persist/kv-put b key new) {:actual actual :expected expected :conflict true}))))
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; create-only: put a value only if the key is absent; conflict if it exists
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(define
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persist/kv-put-new
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(fn
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(b key val)
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(if (persist/kv-has? b key) {:actual (persist/kv-get b key) :conflict true :reason "exists"} (persist/kv-put b key val))))
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