Flush Redis prevnext cache when clearing civicrm_cache

[eileenmcnaughton]

Overview

Flush Redis prevnext cache when clearing civicrm_cache

Before

There is actually nowhere in CiviCRM where the Redis Prev-next cache is flushed. It is possible to flush using eval - ie

 cv php:eval "\Civi::service('prevnext')->deleteItem();"

but in normal operations it is never flushed

After

It would be flushed in the same instances as the civicrm-cache table is cleared

Technical Details

Once we get Redis to start expiring it won't be so necessary to flush the cache - but it should be possible to flush it 'somehow' via the api/ I'm a bit on the fence between this & something a bit more opt-in.

Comments

[civibot]

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[johntwyman]

I'm entirely comfortable with the Redis cache being cleared at the same time.

[totten]

I think the comment is correct - clearing civicrm_cache in the normal case implies that you can clear prevnext in the Redis case. It should be said that this isn't really parity between SQL and Redis. For that, it would need something like:

1. When flushing, delete all Redis keys based on the site-prefix.
2. Fix the oddball Redis keys which lack site-prefix. (Like, ahem, prevnext...)

(Ok, for completeness, another way to reach parity is to rework the prefixes -- instead of literal site-prefix, map each prefix to redis database id. Then FLUSHDB or SWAPDB become options. But that's not easier.)

Anyway, it certainly sounds more conservative (safer) to just flush the part you care about. And in that approach, I'm quite glad there's a comment to explain the thinking. (These cache-clear functions are a bit of maze, and you often have to scratch your head at each junction of the maze.)

[totten]

I'm a bit on the fence between this & something a bit more opt-in.

I think it's functionally safe to merge. Flagging "Merge ready" (in case you want to mull any further).

[seamuslee001]

ok this has been merge ready long enough