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[mod] [DEPRECATED] Remove ability to freeze new data using experiment…
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…al `cache` feature

This commit is BREAKING for those still actively using `nippy/cache`.

Data previously frozen using `nippy/cache` can still be thawed, though
support for thawing may also be removed in a future Nippy version.

Motivation for removal:

  This cache feature (marked as experimental) was always a bit dubious.
  The use cases were very limited, and the complexity quite significant.

  I don't believe that the feature has ever had much (any?) public
  adoption, so I'm removing it here.

  PLEASE LET ME KNOW if this removal negatively impacts you.
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@ptaoussanis
ptaoussanis committed Aug 1, 2023
1 parent 48e62c6 commit 6378fc4
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128 changes: 26 additions & 102 deletions src/taoensso/nippy.clj
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Original file line number Diff line number Diff line change
Expand Up @@ -196,20 +196,21 @@
;; Necessarily without size information
81 [:type nil]
82 [:prefixed-custom-md nil]
59 [:cached-0 nil]
63 [:cached-1 nil]
64 [:cached-2 nil]
65 [:cached-3 nil]
66 [:cached-4 nil]
72 [:cached-5 nil]
73 [:cached-6 nil]
74 [:cached-7 nil]
67 [:cached-sm nil]
68 [:cached-md nil]

;;; DEPRECATED (only support thawing)
;; Desc-sorted by deprecation date

59 [:cached-0_ nil] ; [2022-10-14 v3.3.0]
63 [:cached-1_ nil] ; [2022-10-14 v3.3.0]
64 [:cached-2_ nil] ; [2022-10-14 v3.3.0]
65 [:cached-3_ nil] ; [2022-10-14 v3.3.0]
66 [:cached-4_ nil] ; [2022-10-14 v3.3.0]
72 [:cached-5_ nil] ; [2022-10-14 v3.3.0]
73 [:cached-6_ nil] ; [2022-10-14 v3.3.0]
74 [:cached-7_ nil] ; [2022-10-14 v3.3.0]
67 [:cached-sm_ nil] ; [2022-10-14 v3.3.0]
68 [:cached-md_ nil] ; [2022-10-14 v3.3.0]

78 [:sym-md_ [[:bytes {:read 4}]]] ; [2020-11-18 v3.1.1] Buggy size field, Ref. #138
77 [:kw-md_ [[:bytes {:read 4}]]] ; [2020-11-18 v3.1.1] Buggy size field, Ref. #138

Expand Down Expand Up @@ -945,86 +946,16 @@
(write-id ~'out ~id)
~@body)))

;;;; Caching ; Experimental

;; Nb: don't use an auto initialValue; can cause thread-local state to
;; accidentally hang around with the use of `freeze-to-out!`, etc.
;; Safer to require explicit activation through `with-cache`.
(def ^ThreadLocal -cache-proxy
"{[<x> <meta>] <idx>} for freezing, {<idx> <x-with-meta>} for thawing."
(proxy [ThreadLocal] []))
;;;; Caching (deprecated)

(def ^ThreadLocal -cache-proxy (proxy [ThreadLocal] []))
(defmacro ^:private with-cache
"Experimental, subject to change.
Executes body with support for freezing/thawing cached values.
This is a low-level util: you won't need to use this yourself unless
you're using `freeze-to-out!` or `thaw-from-in!` (also low-level utils).
See also `cache`."
[& body]
`(try
(.set -cache-proxy (volatile! nil))
(do ~@body)
(finally (.remove -cache-proxy))))

(deftype Cached [val])
(defn cache
"Experimental, subject to change.
Wraps value so that future writes of the same wrapped value with same
metadata will be efficiently encoded as references to this one.
(freeze [(cache \"foo\") (cache \"foo\") (cache \"foo\")])
will incl. a single \"foo\", plus 2x single-byte references to \"foo\"."
[x]
(if (instance? Cached x) x (Cached. x)))

(comment (cache "foo"))

(freezer Cached
(let [x-val (.-val x)]
(if-let [cache_ (.get -cache-proxy)]
(let [cache @cache_
k #_x-val [x-val (meta x-val)] ; Also check meta for equality
?idx (get cache k)
^int idx (or ?idx
(let [idx (count cache)]
(vswap! cache_ assoc k idx)
idx))

first-occurance? (nil? ?idx)]

(enc/cond
(sm-count? idx)
(case (int idx)
0 (do (write-id out id-cached-0) (when first-occurance? (-freeze-with-meta! x-val out)))
1 (do (write-id out id-cached-1) (when first-occurance? (-freeze-with-meta! x-val out)))
2 (do (write-id out id-cached-2) (when first-occurance? (-freeze-with-meta! x-val out)))
3 (do (write-id out id-cached-3) (when first-occurance? (-freeze-with-meta! x-val out)))
4 (do (write-id out id-cached-4) (when first-occurance? (-freeze-with-meta! x-val out)))
5 (do (write-id out id-cached-5) (when first-occurance? (-freeze-with-meta! x-val out)))
6 (do (write-id out id-cached-6) (when first-occurance? (-freeze-with-meta! x-val out)))
7 (do (write-id out id-cached-7) (when first-occurance? (-freeze-with-meta! x-val out)))

(do
(write-id out id-cached-sm)
(write-sm-count out idx)
(when first-occurance? (-freeze-with-meta! x-val out))))

(md-count? idx)
(do
(write-id out id-cached-md)
(write-md-count out idx)
(when first-occurance? (-freeze-with-meta! x-val out)))

:else
;; (throw (ex-info "Max cache size exceeded" {:idx idx}))
(-freeze-with-meta! x-val out) ; Just freeze uncached
))

(-freeze-with-meta! x-val out))))

(declare thaw-from-in!)
(def ^:private thaw-cached
(let [not-found (Object.)]
Expand All @@ -1039,13 +970,6 @@
(throw (ex-info "No cache_ established, can't thaw. See `with-cache`."
{}))))))

(comment
(thaw (freeze [(cache "foo") (cache "foo") (cache "foo")]))
(let [v1 (with-meta [] {:id :v1})
v2 (with-meta [] {:id :v2})]
(mapv meta
(thaw (freeze [(cache v1) (cache v2) (cache v1) (cache v2)])))))

;;;;

(id-freezer nil id-nil)
Expand Down Expand Up @@ -1233,7 +1157,7 @@
[x]
(let [baos (ByteArrayOutputStream. 64)
dos (DataOutputStream. baos)]
(with-cache (-freeze-with-meta! x dos))
(-freeze-with-meta! x dos)
(.toByteArray baos)))

(defn freeze
Expand Down Expand Up @@ -1261,11 +1185,11 @@
(when-not no-header? ; Avoid `wrap-header`'s array copy:
(let [head-ba (get-head-ba {:compressor-id nil :encryptor-id nil})]
(.write dos head-ba 0 4)))
(with-cache (-freeze-with-meta! x dos))
(-freeze-with-meta! x dos)
(.toByteArray baos))

(do
(with-cache (-freeze-with-meta! x dos))
(-freeze-with-meta! x dos)
(let [ba (.toByteArray baos)

compressor
Expand Down Expand Up @@ -1535,16 +1459,16 @@
(with-meta (thaw-from-in! in) m)
(do (thaw-from-in! in))))

id-cached-0 (thaw-cached 0 in)
id-cached-1 (thaw-cached 1 in)
id-cached-2 (thaw-cached 2 in)
id-cached-3 (thaw-cached 3 in)
id-cached-4 (thaw-cached 4 in)
id-cached-5 (thaw-cached 5 in)
id-cached-6 (thaw-cached 6 in)
id-cached-7 (thaw-cached 7 in)
id-cached-sm (thaw-cached (read-sm-count in) in)
id-cached-md (thaw-cached (read-md-count in) in)
id-cached-0_ (thaw-cached 0 in)
id-cached-1_ (thaw-cached 1 in)
id-cached-2_ (thaw-cached 2 in)
id-cached-3_ (thaw-cached 3 in)
id-cached-4_ (thaw-cached 4 in)
id-cached-5_ (thaw-cached 5 in)
id-cached-6_ (thaw-cached 6 in)
id-cached-7_ (thaw-cached 7 in)
id-cached-sm_ (thaw-cached (read-sm-count in) in)
id-cached-md_ (thaw-cached (read-md-count in) in)

id-bytes-0 (byte-array 0)
id-bytes-sm (read-bytes in (read-sm-count in))
Expand Down
38 changes: 0 additions & 38 deletions test/taoensso/nippy/tests/main.clj
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Original file line number Diff line number Diff line change
Expand Up @@ -133,44 +133,6 @@
(let [mr (MyRec. "basic" "fancy")]
(= mr (thaw (freeze mr))))))))

;;;; Caching

(deftest _caching
(let [stress [nippy/stress-data-comparable
nippy/stress-data-comparable
nippy/stress-data-comparable
nippy/stress-data-comparable]
cached (mapv nippy/cache stress)
cached (mapv nippy/cache stress) ; <=1 wrap auto-enforced
]

(is (= stress (thaw (freeze stress {:compressor nil}))))
(is (= stress (thaw (freeze cached {:compressor nil}))))
(let [size-stress (count (freeze stress {:compressor nil}))
size-cached (count (freeze cached {:compressor nil}))]
(is (>= size-stress (* 3 size-cached)))
(is (< size-stress (* 4 size-cached))))))

(deftest _caching-metadata
(let [v1 (with-meta [] {:id :v1})
v2 (with-meta [] {:id :v2})

frozen-without-caching (freeze [v1 v2 v1 v2])
frozen-with-caching
(freeze [(nippy/cache v1)
(nippy/cache v2)
(nippy/cache v1)
(nippy/cache v2)])]

(is (> (count frozen-without-caching)
(count frozen-with-caching)))

(is (= (thaw frozen-without-caching)
(thaw frozen-with-caching)))

(is (= (mapv meta (thaw frozen-with-caching))
[{:id :v1} {:id :v2} {:id :v1} {:id :v2}]))))

;;;; Stable binary representation of vals

(deftest _stable-bin
Expand Down
38 changes: 0 additions & 38 deletions test/taoensso/nippy_tests.clj
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Original file line number Diff line number Diff line change
Expand Up @@ -137,44 +137,6 @@
(let [mr (MyRec. "basic" "fancy")]
(= mr (thaw (freeze mr)))))))])

;;;; Caching

(deftest _caching
(let [stress [nippy/stress-data-comparable
nippy/stress-data-comparable
nippy/stress-data-comparable
nippy/stress-data-comparable]
cached (mapv nippy/cache stress)
cached (mapv nippy/cache stress) ; <=1 wrap auto-enforced
]

(is (= stress (thaw (freeze stress {:compressor nil}))))
(is (= stress (thaw (freeze cached {:compressor nil}))))
(let [size-stress (count (freeze stress {:compressor nil}))
size-cached (count (freeze cached {:compressor nil}))]
(is (>= size-stress (* 3 size-cached)))
(is (< size-stress (* 4 size-cached))))))

(deftest _caching-metadata
(let [v1 (with-meta [] {:id :v1})
v2 (with-meta [] {:id :v2})

frozen-without-caching (freeze [v1 v2 v1 v2])
frozen-with-caching
(freeze [(nippy/cache v1)
(nippy/cache v2)
(nippy/cache v1)
(nippy/cache v2)])]

(is (> (count frozen-without-caching)
(count frozen-with-caching)))

(is (= (thaw frozen-without-caching)
(thaw frozen-with-caching)))

(is (= (mapv meta (thaw frozen-with-caching))
[{:id :v1} {:id :v2} {:id :v1} {:id :v2}]))))

;;;; Stable binary representation of vals

(deftest _stable-bin
Expand Down

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