[Tree widget]: add abstract batching cache on next

[JonasDov]

When reviewing #1678,
Realized I hadn't included the ChildElementsCache rewrite in the original phases. Thinking we could insert it between phase 1 and phase 2.

While trying to implement ChildElementsCache, considered unifying how it works with DescendantCountsCache. Currently ChildElementsCache executes a query per request, while DescendantCountsCache batches requests over a 20ms window. The original plan was to keep the structure as-is, but decided that it's better to batch ChildElementsCache as well.

This PR includes:

1. Abstract BatchingCache class which is used by DescendantCountsCache.
2. DescendantCountsCache changes to use BatchingCache.

Afterwards will create a separate PR for adjusting ChildElementsCache.

[Copilot]

Pull request overview

Extracts the timer-based batching, deduplication, and caching logic from DescendantsCountCache into a new abstract BatchingCache base class so the same machinery can later be reused by ChildElementsCache (to be done in a follow-up PR). DescendantsCountCache is refactored to extend the new base class, exposing its specifics (batch shape, query building, row insertion) via protected hooks.

Changes:

• Add new BatchingCache<TRequest, TBatch, TResult, TItem, TRow> abstract class that owns the 20ms batch timer, in-flight deduplication, buffer-and-query pipeline, and result/caching plumbing (configurable buffer size, timer delay, release-on-count).
• Refactor DescendantsCountCache to extend BatchingCache, implementing getCachedValue/getGuaranteedCachedValue/getValuesToRequest/createBatch/addRequestToBatch/getIterable/executeQuery/insertRow/ensureDefaultCacheEntries, and exposing getDescendantsCounts as a thin wrapper over get.
• Introduce supporting DescendantsCountRequest, DescendantsCountResult, Batch, WhereClause, and Row types in DescendantsCountCache.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
packages/itwin/tree-widget/src/tree-widget-react/components/trees/common/internal/caches/BatchingCache.ts	New abstract base class encapsulating batching, deduplication, and caching shared between caches.
packages/itwin/tree-widget/src/tree-widget-react/components/trees/common/internal/caches/DescendantsCountCache.ts	Refactored to extend BatchingCache, with previously-inline batching/query logic moved into protected hooks.

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[github-actions]

Tree-Widget Next benchmark

Benchmark suite	Current: c8a3ab5	Previous: 45b95b4	Deviation	Status
models tree 50k 3D elements search > get search paths	1218 ms	1274 ms	-4.40%	〰️
models tree 50k 3D elements search > get search paths (P95 of main thread blocks)	54 ms	53 ms	1.89%	〰️
models tree 50k 3D elements search > load hierarchy from search paths	113223 ms	114168 ms	-0.83%	〰️
models tree 50k 3D elements search > load hierarchy from search paths (P95 of main thread blocks)	41 ms	40 ms	2.50%	〰️
models tree 50k categories > collect nodes	2814 ms	3000 ms	-6.20%	〰️
models tree 50k categories > collect nodes (P95 of main thread blocks)	127 ms	106 ms	19.81%	〰️
models tree 50k categories > validate initial visibility	2569 ms	2588 ms	-0.73%	〰️
models tree 50k categories > validate initial visibility (P95 of main thread blocks)	0 ms	0 ms	0%	🟰
models tree 50k categories > change visibility	71 ms	75 ms	-5.33%	〰️
models tree 50k categories > change visibility (P95 of main thread blocks)	60 ms	64 ms	-6.25%	〰️
models tree 50k categories > validate changed visibility	4794 ms	4691 ms	2.20%	〰️
models tree 50k categories > validate changed visibility (P95 of main thread blocks)	31 ms	26 ms	19.23%	〰️
models tree 50k 3D elements > collect nodes	45542 ms	45626 ms	-0.18%	〰️
models tree 50k 3D elements > collect nodes (P95 of main thread blocks)	71 ms	67 ms	5.97%	〰️
models tree 50k 3D elements > validate initial visibility	2489 ms	2549 ms	-2.35%	〰️
models tree 50k 3D elements > validate initial visibility (P95 of main thread blocks)	0 ms	0 ms	0%	🟰
models tree 50k 3D elements > change model visibility	19 ms	21 ms	-9.52%	〰️
models tree 50k 3D elements > change model visibility (P95 of main thread blocks)	0 ms	0 ms	0%	🟰
models tree 50k 3D elements > validate changed model visibility	2585 ms	2564 ms	0.82%	〰️
models tree 50k 3D elements > validate changed model visibility (P95 of main thread blocks)	24 ms	0 ms	2400%	〰️
models tree 50k 3D elements > change category node visibility	527 ms	503 ms	4.77%	〰️
models tree 50k 3D elements > change category node visibility (P95 of main thread blocks)	59 ms	52 ms	13.46%	〰️
models tree 50k 3D elements > validate changed category visibility	2515 ms	2575 ms	-2.33%	〰️
models tree 50k 3D elements > validate changed category visibility (P95 of main thread blocks)	0 ms	0 ms	0%	🟰
models tree 50k 3D elements > validate per-model category override	2518 ms	2501 ms	0.68%	〰️
models tree 50k 3D elements > validate per-model category override (P95 of main thread blocks)	0 ms	0 ms	0%	🟰
models tree 50k 3D elements > change element visibility	9 ms	10 ms	-10%	〰️
models tree 50k 3D elements > change element visibility (P95 of main thread blocks)	0 ms	0 ms	0%	🟰
models tree 50k 3D elements > validate changed element visibility	3211 ms	3269 ms	-1.77%	〰️
models tree 50k 3D elements > validate changed element visibility (P95 of main thread blocks)	83 ms	71 ms	16.90%	〰️
models tree 50k 3D child elements with different categories > collect nodes	45175 ms	46013 ms	-1.82%	〰️
models tree 50k 3D child elements with different categories > collect nodes (P95 of main thread blocks)	55 ms	64 ms	-14.06%	〰️
models tree 50k 3D child elements with different categories > validate initial visibility	2479 ms	2478 ms	0.04%	〰️
models tree 50k 3D child elements with different categories > validate initial visibility (P95 of main thread blocks)	0 ms	0 ms	0%	🟰
models tree 50k 3D child elements with different categories > change visibility	11 ms	10 ms	10%	〰️
models tree 50k 3D child elements with different categories > change visibility (P95 of main thread blocks)	0 ms	0 ms	0%	🟰
models tree 50k 3D child elements with different categories > validate changed visibility	3096 ms	3264 ms	-5.15%	〰️
models tree 50k 3D child elements with different categories > validate changed visibility (P95 of main thread blocks)	67 ms	81 ms	-17.28%	〰️
categories tree 50k subCategories search > get search paths	1887 ms	1924 ms	-1.92%	〰️
categories tree 50k subCategories search > get search paths (P95 of main thread blocks)	44 ms	45 ms	-2.22%	〰️
categories tree 50k subCategories search > load hierarchy from search paths	5432 ms	5581 ms	-2.67%	〰️
categories tree 50k subCategories search > load hierarchy from search paths (P95 of main thread blocks)	47 ms	51 ms	-7.84%	〰️
categories tree 50k subCategories > collect nodes	6060 ms	6044 ms	0.26%	〰️
categories tree 50k subCategories > collect nodes (P95 of main thread blocks)	48 ms	49 ms	-2.04%	〰️
categories tree 50k subCategories > validate initial visibility	1684 ms	1703 ms	-1.12%	〰️
categories tree 50k subCategories > validate initial visibility (P95 of main thread blocks)	21 ms	22 ms	-4.55%	〰️
categories tree 50k subCategories > change visibility	344 ms	348 ms	-1.15%	〰️
categories tree 50k subCategories > change visibility (P95 of main thread blocks)	21 ms	0 ms	2100%	〰️
categories tree 50k subCategories > validate changed visibility	1639 ms	1620 ms	1.17%	〰️
categories tree 50k subCategories > validate changed visibility (P95 of main thread blocks)	36 ms	31 ms	16.13%	〰️
categories tree 50k categories > collect nodes	2455 ms	2535 ms	-3.16%	〰️
categories tree 50k categories > collect nodes (P95 of main thread blocks)	124 ms	135 ms	-8.15%	〰️
categories tree 50k categories > validate initial visibility	7480 ms	7428 ms	0.70%	〰️
categories tree 50k categories > validate initial visibility (P95 of main thread blocks)	92 ms	70 ms	31.43%	〰️
categories tree 50k categories > change visibility	704 ms	706 ms	-0.28%	〰️
categories tree 50k categories > change visibility (P95 of main thread blocks)	49 ms	53 ms	-7.55%	〰️
categories tree 50k categories > validate changed visibility	7509 ms	7403 ms	1.43%	〰️
categories tree 50k categories > validate changed visibility (P95 of main thread blocks)	41 ms	41 ms	0%	🟰
classifications tree 50k classifications search > get search paths	2117 ms	2223 ms	-4.77%	〰️
classifications tree 50k classifications search > get search paths (P95 of main thread blocks)	138 ms	131 ms	5.34%	〰️
classifications tree 50k classifications search > load hierarchy from search paths	69987 ms	69563 ms	0.61%	〰️
classifications tree 50k classifications search > load hierarchy from search paths (P95 of main thread blocks)	26 ms	21 ms	23.81%	〰️
classifications tree 50k classifications > collect nodes	40746 ms	37771 ms	7.88%	〰️
classifications tree 50k classifications > collect nodes (P95 of main thread blocks)	89 ms	102 ms	-12.75%	〰️
classifications tree 50k classifications > validate initial visibility	5104 ms	4962 ms	2.86%	〰️
classifications tree 50k classifications > validate initial visibility (P95 of main thread blocks)	97 ms	63 ms	53.97%	〰️
classifications tree 50k classifications > change visibility	44 ms	31 ms	41.94%	〰️
classifications tree 50k classifications > change visibility (P95 of main thread blocks)	22 ms	0 ms	2200%	〰️
classifications tree 50k classifications > validate changed visibility	5137 ms	5118 ms	0.37%	〰️
classifications tree 50k classifications > validate changed visibility (P95 of main thread blocks)	68 ms	71 ms	-4.23%	〰️

This comment was automatically generated by workflow using github-action-benchmark.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.