[dev] Column cache "async" isn't dynamic about visidata HOT 4 CLOSED

That's right, cache="async" means to cache the column (make it non-dynamic), but do the caching asynchronously (in other threads). This is meant for long-running operations so that they're only done once and don't freeze up the interface. z' should reset the cache manually if you want the results to change.

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thanks @saulpw . i didn't know about z'.

though it feels like caching on and async on could be orthogonal. that is, in this case i want cache off and async on. that is, asynchrony isn't a cache strategy it is an execution strategy.

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Well, that wouldn't work how you want either, because VisiData recalculates its cells on every draw cycle. For a quick demonstration of this, try =random(). It settles down after a second or so, but then will restart on every command, including movement. If we allowed "cache off and async on" as you suggest, it would spawn dozens of threads for each command.

Of course, we could have it recalc only when the sheet is modified. But the sheet is also considered modified more often than you would think--for instance, when you hide a column. So by default we assume calculations are not expensive, and if they are expensive, then they are expensive enough to be cached until the user triggers a cache reset.

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because VisiData recalculates its cells on every draw cycle.

i noticed that the first time i derived a new column with a function that made a REST call over the wire. yikes!

but i memoized the function and that worked well. that was before i saw the cache Column option.

maybe i can get the behavior i am looking for by triggering a resetCache on some cues.

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