Optimize FindQuery.update() with partial writes

[lh0156]

Summary

Implements #777 by updating matching records without materializing full Pydantic models.

What changed

• Uses FT.SEARCH ... NOCONTENT to collect matching keys page by page.
• Validates and serializes update values once, including Pydantic constraints and Redis OM storage conversions.
• Uses partial HSET mappings for HashModel.
• Uses path-level JSON.SET commands for JsonModel, including nested __ paths.
• Preserves the use_transaction flag and returns the number of updated records.
• Keeps query projections out of the key-only search and preserves KNN state when copying queries.
• Documents the new return value.

Testing

• pytest -q tests --ignore tests/test_benchmarks.py: 265 passed.
• pytest -q tests/test_hash_model.py tests/test_json_model.py: 147 passed.
• Generated sync tests for the new coverage plus Hash/JSON model tests: 157 passed.
• ruff check and ruff format --check on changed source/tests.
• python -m compileall -q aredis_om tests.
• bandit -q -r aredis_om/model/model.py -s B608.

Redis Stack was run locally via Docker Compose for the integration tests; benchmark tests were excluded from the full run.

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Note

Medium Risk
Bulk updates now bypass per-instance save() and write directly to Redis, so behavior depends on the new serialization and TTL preservation matching prior semantics; scope is contained to FindQuery.update() with broad test coverage.

Overview
FindQuery.update() no longer loads full models and re-saves them. It validates and serializes update values once, pages FT.SEARCH … NOCONTENT to collect matching keys (ignoring .only() projections), then applies partial HSET mappings for HashModel or JSON.SET on dotted paths (including __ nested fields) for JsonModel. Hash updates re-apply HEXPIRE for fields that had a positive TTL. The method now returns the count of updated records; docs reflect that.

FindQuery.dict() / copy() also persist knn when cloning queries for the key-only search path.

New unit tests cover validation-before-search, empty hash mappings, pagination, JSON paths, and Pydantic v1 field resolution; an integration test asserts bulk update preserves hash field TTLs.

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[abrookins]

Thanks for opening, @lh0156! I'll take a look ASAP.

[cursor]

Cursor Bugbot has reviewed your changes using default effort and found 1 potential issue.

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