feat(stores/redis): use GETEX on Redis >= 6.2 for get+renew

[Karunasagar12]

Summary

Closes #4993 — on Redis 6.2+, GETEX atomically gets a value and sets its expiry in a single command, eliminating the Lua script overhead.

Changes

litestar/stores/redis.py:

1. Added _check_getex_support() — lazily detects Redis server version via INFO server on first get() call with renew_for. Result is cached for the lifetime of the store instance.
2. get() now uses GETEX key EX <seconds> when Redis >= 6.2, falling back to the existing Lua script on older versions.
3. Bug fix: Changed renew_for.seconds to int(renew_for.total_seconds()). The old code used timedelta.seconds which only returns the seconds component, not total seconds — timedelta(days=1, seconds=5).seconds == 5, not 86405.

tests/unit/test_stores.py:

Test	What it verifies
test_get_and_renew_redis_uses_getex	Version detection works, GETEX path is taken, TTL is renewed
test_get_and_renew_redis_lua_fallback	Lua script still works when GETEX is unsupported
test_get_renew_for_timedelta_uses_total_seconds	timedelta conversion uses total_seconds()

Backward Compatibility

• Redis < 6.2: falls back to existing Lua script (no behavior change)
• Redis >= 6.2: same semantics, fewer round-trips
• Version check uses a single cached INFO server call (negligible cost)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 67.17%. Comparing base (b18a21f) to head (ce2b4b2).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4996      +/-   ##
==========================================
- Coverage   67.17%   67.17%   -0.01%     
==========================================
  Files         293      293              
  Lines       15354    15352       -2     
  Branches     1744     1744              
==========================================
- Hits        10314    10312       -2     
  Misses       4890     4890              
  Partials      150      150              

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[sobolevn]

I think 3.0.0 is the right time to drop older redis versions support.

6.0 https://redis.io/docs/latest/operate/rs/release-notes/rs-6-0-may-2020/ was released 6 years ago.
and 6.1 never existed.

[Karunasagar12]

Good call — updated. Dropped the Lua script and version detection entirely. get() now just calls GETEX directly.

Also fixed a pre-existing bug while I was in there: the old code used timedelta.seconds (which only returns the seconds component) instead of int(total_seconds()). So renew_for=timedelta(days=1) was silently renewing for 0 seconds.

[sobolevn]

This would require a deprecation message in 2.x branch

[provinzkraut]

I think 3.0.0 is the right time to drop older redis versions support.

6.0 https://redis.io/docs/latest/operate/rs/release-notes/rs-6-0-may-2020/ was released 6 years ago. and 6.1 never existed.

I'm still stuck at 6.0 at work.. 😬
And I'm sure I'm not the only one. I'd rather we keep it unless there's a good reason against dropping it?