perf: use deque for iterator object cache

[giulio-leone]

Problem

Both _ObjectIterator.__next__() and _ObjectAIterator.__anext__() consume cached objects front-to-back via list.pop(0), which is O(n) per removal. With the default ITERATOR_CACHE_SIZE (typically 100), each batch drain is O(n²).

Solution

Switch __iter_object_cache from list to collections.deque, replacing .pop(0) with .popleft() for O(1) front removal. The res.objects list returned by fetch_objects() is wrapped in deque() on assignment.

Changes

• weaviate/collections/iterator.py:
  • Import deque from collections
  • _ObjectIterator: type, init, __iter__, __next__ updated
  • _ObjectAIterator: type, init, __aiter__, __anext__ updated
  • .pop(0) → .popleft()

Testing

• Syntax verified via ast.parse()

[orca-security-eu]

Orca Security Scan Summary

Status	Check	Issues by priority
Passed	Infrastructure as Code	0   0   0   0	View in Orca
Passed	SAST	0   0   0   0	View in Orca
Passed	Secrets	0   0   0   0	View in Orca
Passed	Vulnerabilities	0   0   0   0	View in Orca

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[giulio-leone]

I have read the Contributor License Agreement and I agree to its terms.

[dirkkul]

Thanks for this! Could you fix the linter/formatting issues? Then we can merge it

[Copilot]

Pull request overview

This PR optimizes object iteration in the collections layer by replacing an internal list-based cache (with O(n) front removals) with a collections.deque (O(1) front removals), improving performance when draining iterator batches.

Changes:

• Switch iterator object caches in _ObjectIterator and _ObjectAIterator from list to collections.deque.
• Replace pop(0) calls with popleft() and wrap fetched res.objects in deque(...) on assignment.

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[giulio-leone]

Fixed the linting/formatting issues (removed unused List import flagged by ruff F401) — should be good to merge now. Thanks for the review!