[evanchooly]

Plan items 3.4 and 3.5. The plan notes that 3.4, a one-line fix, can ride along with any PR, so each has its own commit here.

3.4: getProperty does one lookup

EntityModel.getProperty used propertyModelsByMappedName.getOrDefault(name, propertyModelsByName.get(name)). The default argument is evaluated eagerly, so it probed the second map on every call, including once per decoded field. It now checks the mapped-name map first and falls back only on a miss. The result is the same, since neither map holds null values.

3.5: memoize codec lookups by class

The driver's ProvidersCodecRegistry.get(Class) allocates several objects on every call just to find a codec it has already cached: a ChildCodecRegistry, a CodecCacheKey, an Optional and a capturing lambda. Morphia looks codecs up per value, for array elements, map values, references, untyped properties and subtype values. Three changes:

• MemoizingCodecRegistry (@MorphiaInternal) wraps the datastore's registry. A repeat get(Class) is a single ConcurrentHashMap hit. It uses get + putIfAbsent rather than computeIfAbsent, because building a codec can recurse into lookups. Failed lookups aren't cached. Lookups that take type arguments or a registry depend on their context, so they go straight to the wrapped registry. The driver caches one codec per class and returns the cached instance, and that's the instance memoized here, so results are unchanged. This also covers the driver's own per-operation lookups through database.withCodecRegistry.
• MorphiaCodec.codecForSubtype(Class) caches the codec for each subtype value encoded through a codec. EntityEncoder and LifecycleEncoder use it instead of the codec's composite fromRegistries(...) registry, which is a driver registry and so allocates on every lookup.
• ArrayCodec resolves its component codec once, instead of once per element. The cache field is volatile because the codec is shared across threads. EntityDecoder's cached peekId codec from Resolve discriminators to codecs once per codec (plan item 3.3) #4405 gets the same fix.

Tests

• TestMemoizingCodecRegistry uses a counting delegate to check three things:
  • repeated get(String.class) calls reach the delegate once and return the same codec;
  • a failing lookup isn't cached, so it fails each time;
  • contextual get(Class, CodecRegistry) lookups always reach the delegate.
• The harness, creator and discriminator tests are unchanged and pass. The core and Kotlin suites pass with -Dmorphia.mapper=critter and with reflection: 1492 + 5 tests, 0 failures.

JMH: CodecBenchmark, master (05862218aea) vs this branch

Same machine as the baseline (i9-11900H, Temurin 17), -prof gc, the benchmark's own settings (3 forks × 5 × 1 s). Before and after ran back to back with nothing else running. Critter is the AOT variant.

reflection

benchmark	model	before ns/op	after ns/op	Δ time	before B/op	after B/op	Δ alloc
decode	ARRAYS	69,196 ± 483	68,390 ± 3,149	-1.2%	77,378	74,849	-3.3%
decode	COLLECTIONS	9,091 ± 254	8,242 ± 64	-9.3%	16,824	16,712	-0.7%
decode	CONCRETE_COLLECTIONS	3,015 ± 53	2,818 ± 89	-6.5%	6,272	6,128	-2.3%
decode	LAZY_REFERENCE	3,260 ± 136	3,120 ± 124	-4.3%	7,755	7,293	-5.9%
decode	LIFECYCLE	1,138 ± 27	1,063 ± 29	-6.6%	2,851	2,840	-0.4%
decode	NESTED	3,015 ± 88	2,818 ± 33	-6.5%	5,776	5,656	-2.1%
decode	POLYMORPHIC	5,461 ± 54	5,048 ± 64	-7.6%	9,656	9,528	-1.3%
decode	SIMPLE	1,216 ± 14	1,102 ± 15	-9.4%	2,256	2,136	-5.3%
decodeInCursor	ARRAYS	68,529 ± 509	67,378 ± 708	-1.7%	77,066	74,546	-3.3%
decodeInCursor	COLLECTIONS	9,034 ± 126	8,347 ± 96	-7.6%	16,504	16,384	-0.7%
decodeInCursor	CONCRETE_COLLECTIONS	3,071 ± 65	2,928 ± 72	-4.7%	5,968	5,848	-2.0%
decodeInCursor	LAZY_REFERENCE	3,530 ± 42	3,260 ± 37	-7.7%	7,507	7,005	-6.7%
decodeInCursor	LIFECYCLE	1,178 ± 38	1,120 ± 26	-4.9%	2,536	2,528	-0.3%
decodeInCursor	NESTED	3,200 ± 269	2,819 ± 103	-11.9%	5,464	5,344	-2.2%
decodeInCursor	POLYMORPHIC	5,565 ± 77	5,140 ± 109	-7.6%	9,336	9,216	-1.3%
decodeInCursor	SIMPLE	1,185 ± 34	1,137 ± 38	-4.0%	1,944	1,824	-6.2%
encode	ARRAYS	96,905 ± 1,853	97,915 ± 1,481	+1.0%	137,198	135,598	-1.2%
encode	COLLECTIONS	7,774 ± 88	7,575 ± 74	-2.6%	7,400	7,336	-0.9%
encode	CONCRETE_COLLECTIONS	2,060 ± 34	2,030 ± 31	-1.5%	3,136	3,104	-1.0%
encode	LAZY_REFERENCE	1,806 ± 19	1,809 ± 78	+0.2%	4,083	3,885	-4.8%
encode	LIFECYCLE	827 ± 8	802 ± 15	-3.1%	3,043	3,064	+0.7%
encode	NESTED	2,281 ± 24	2,248 ± 44	-1.4%	1,856	1,856	-0.0%
encode	POLYMORPHIC	4,293 ± 33	4,032 ± 71	-6.1%	6,024	4,584	-23.9%
encode	SIMPLE	798 ± 12	777 ± 11	-2.6%	1,216	1,216	-0.0%

critter

benchmark	model	before ns/op	after ns/op	Δ time	before B/op	after B/op	Δ alloc
decode	ARRAYS	67,049 ± 741	66,715 ± 840	-0.5%	77,378	74,858	-3.3%
decode	COLLECTIONS	8,845 ± 121	8,533 ± 102	-3.5%	16,824	16,688	-0.8%
decode	CONCRETE_COLLECTIONS	3,005 ± 27	2,952 ± 83	-1.7%	6,272	6,128	-2.3%
decode	LAZY_REFERENCE	3,323 ± 47	3,095 ± 96	-6.9%	7,752	7,227	-6.8%
decode	LIFECYCLE	1,126 ± 12	1,056 ± 36	-6.2%	2,840	2,840	-0.0%
decode	NESTED	3,222 ± 139	3,020 ± 52	-6.3%	5,752	5,656	-1.7%
decode	POLYMORPHIC	5,697 ± 72	5,431 ± 115	-4.7%	9,664	9,528	-1.4%
decode	SIMPLE	1,182 ± 74	1,135 ± 36	-4.0%	2,256	2,136	-5.3%
decodeInCursor	ARRAYS	67,135 ± 608	67,103 ± 2,040	-0.0%	77,066	74,546	-3.3%
decodeInCursor	COLLECTIONS	9,157 ± 145	8,776 ± 164	-4.2%	16,504	16,384	-0.7%
decodeInCursor	CONCRETE_COLLECTIONS	3,109 ± 54	2,983 ± 36	-4.1%	5,976	5,840	-2.3%
decodeInCursor	LAZY_REFERENCE	3,397 ± 91	3,114 ± 45	-8.3%	7,453	6,979	-6.4%
decodeInCursor	LIFECYCLE	1,158 ± 21	1,136 ± 21	-1.9%	2,549	2,557	+0.3%
decodeInCursor	NESTED	3,350 ± 153	2,969 ± 44	-11.4%	5,464	5,344	-2.2%
decodeInCursor	POLYMORPHIC	5,770 ± 97	5,480 ± 101	-5.0%	9,336	9,216	-1.3%
decodeInCursor	SIMPLE	1,221 ± 14	1,140 ± 58	-6.7%	1,944	1,824	-6.2%
encode	ARRAYS	95,994 ± 1,289	98,008 ± 3,130	+2.1%	145,784	135,598	-7.0%
encode	COLLECTIONS	7,650 ± 115	7,604 ± 69	-0.6%	7,336	7,336	+0.0%
encode	CONCRETE_COLLECTIONS	2,016 ± 20	2,022 ± 30	+0.3%	3,104	3,147	+1.4%
encode	LAZY_REFERENCE	1,697 ± 17	1,658 ± 16	-2.3%	4,072	3,832	-5.9%
encode	LIFECYCLE	827 ± 19	784 ± 11	-5.3%	3,064	3,043	-0.7%
encode	NESTED	2,348 ± 30	2,306 ± 15	-1.8%	1,856	1,856	-0.0%
encode	POLYMORPHIC	4,290 ± 36	4,023 ± 58	-6.2%	5,640	4,200	-25.5%
encode	SIMPLE	769 ± 27	735 ± 7	-4.4%	1,216	1,216	-0.0%

Reading it:

• POLYMORPHIC encode allocates 1,440 B less (−24% / −25.5%) and runs about 6% faster. That's the 12 subtype values per document no longer going through the driver's registry. The review estimated ~600 B per operation.
• Decode is 4–12% faster on most models, on both mappers. That comes from 3.4's lookup per field, plus the memoized lookups. Decode allocation drops 120 B on SIMPLE, 2.5 KB on ARRAYS (the component codec) and ~500 B on LAZY_REFERENCE (reference lookups).
• No cell moved the wrong way beyond its error bars. The critter encode ARRAYS allocation drop includes that cell's usual outlier before value.

Decisions to review

1. 3.4 and 3.5 ship in one PR, as two commits. The plan allows it for 3.4, and benchmarking a one-line change on its own would cost another hour of JMH. The table measures both together.
2. The memoizing wrapper covers the whole datastore registry, not only Morphia's providers. The driver's own lookups during operations benefit too. The wrapper never invents a codec: it caches what the driver returns, the driver itself keeps exactly one codec per class, and failed lookups aren't cached.

[Copilot]

🟡 Changes recommended

The shared array-component codec cache needs safe publication to preserve initialization visibility during concurrent decoding.

1 open issue

• Make componentCodec volatile for safe publication · New

What changed in this PR

Reduces lookup overhead and allocations in Morphia’s encoding and decoding paths, implementing plan items 3.4 and 3.5.

Changes:

• Avoids unnecessary property-name map lookups.
• Caches class, subtype, and array-component codecs.
• Adds registry-cache tests and marks the plan items complete.

File	Description
design/​mapping-game-plan.md	Marks both optimizations complete.
core/​src/​test/​java/​dev/​morphia/​mapping/​codec/​TestMemoizingCodecRegistry.java	Tests caching, failures, and contextual delegation.
core/​src/​main/​java/​dev/​morphia/​MorphiaDatastore.java	Wraps the datastore registry with memoization.
core/​src/​main/​java/​dev/​morphia/​mapping/​codec/​pojo/​MorphiaCodec.java	Adds subtype codec caching.
core/​src/​main/​java/​dev/​morphia/​mapping/​codec/​pojo/​LifecycleEncoder.java	Uses cached subtype codecs.
core/​src/​main/​java/​dev/​morphia/​mapping/​codec/​pojo/​EntityModel.java	Makes property-name fallback lazy.
core/​src/​main/​java/​dev/​morphia/​mapping/​codec/​pojo/​EntityEncoder.java	Uses cached subtype codecs.
core/​src/​main/​java/​dev/​morphia/​mapping/​codec/​MemoizingCodecRegistry.java	Adds class-based registry memoization.
core/​src/​main/​java/​dev/​morphia/​mapping/​codec/​ArrayCodec.java	Caches the decoding component codec.

_{Review effort: Balanced}

[Copilot]

🟢 Approval recommended

Static review found no blocking issues; lookup semantics are preserved and the prior cache-publication concern is resolved.

No open issues 🎉

1 resolved since last review

• Make componentCodec volatile for safe publication

_{Review effort: Balanced}