Re: index access method documentation light on details on ii_AmCache

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/15/index-functions.html

Description:

So, if I cache something in ii_AmCache during a call to my aminsert

callback...

When, if ever, does it get freed?

Having looked at example code, I don't actually see anything doing this in

insert paths, so presumably there's some point at which this happens

automatically, possibly as part of the Memory Context thing, maybe related

to the ii_Context which seems to be getting used, but I can't find anything

anywhere documenting that. This may well be completely obvious, or intended

to be implied by "it can allocate space in indexInfo->ii_Context", but it's

not exceptionally obvious to me as a newcomer to the code. (By contrast, the

ambuild docs say to palloc a data structure, but don't mention a context for

it; no idea whether it should be in a particular context.)

Actually, in full generality, I have not been able to find a section of the

documentation which explains the memory-context stuff at all. I found a blog

post elsewhere suggesting that it's just "the memory context will be freed

and thus everything associated with it". This implies that there's no

straightforward way for an index to do end-of-insert maintenance after all

the inserts from a given query are complete, except to do it after every

tuple just in case it's the last tuple, I guess?