iemejia opened a new pull request, #3966:
URL: https://github.com/apache/avro/pull/3966
## What changes were proposed in this pull request?
`ObjectCreator.FindType` passed an inline lambda to
`ConcurrentDictionary.GetOrAdd`:
```csharp
return typeCacheByName.GetOrAdd(name, (_) =>
{
...
if (TryGetIListItemTypeName(name, out var itemTypeName)) { ... } //
captures `name`
...
});
```
The lambda discards the key parameter (`(_)`) and instead **captures the
local `name`**. Capturing a local forces the C# compiler to allocate a new
display-class closure (and delegate) on **every** call — including cache hits,
since the factory delegate is constructed as an argument regardless of whether
`GetOrAdd` invokes it. As reported in AVRO-3893, this accounted for ~10% of
allocations on a deserialization hot path using `PreresolvingDatumReader`.
## How was this patch fixed?
- Extract the value factory into a private `FindTypeUncached(string name)`
method.
- Store a single cached `Func<string, Type> findTypeFactory` delegate,
created once in the constructor, and pass it to `GetOrAdd`.
- The factory uses its `name` parameter (the cache key supplied by
`GetOrAdd`) instead of a captured local, so **no closure is allocated per
lookup**.
`ObjectCreator` is a shared singleton (`ObjectCreator.Instance`), so the
factory delegate is effectively allocated once for the process. Behaviour is
unchanged; the `CA1031` suppression is retargeted from `FindType` to the
extracted `FindTypeUncached`.
## How was this patch tested?
- `dotnet build` of `Avro.main` succeeds with 0 warnings (confirming the
retargeted suppression).
- `Avro.test` Specific/ObjectCreator suites pass: **96/96** across net6.0,
net7.0, and net8.0.
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