cacheutil: fix computation of entry size

[rafiss]

fixes #89444

The previous way would always result in a fixed size for each entry, since it would just compute the size of a pointer. Now, the size of the entry must be specified when writing to the cache.

Release note: None

[cockroach-teamcity]

This change is 

[ZhouXing19]

LGTM, but just to make sure I understood it

1. The bound account need to increase the size by the sum of the key's and value's size
2. For a descriptor, its size should include those for the users.
   Is it correct?

Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @rafiss)

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pkg/sql/cacheutil/cache.go line 85 at r1 (raw file):

// version than the one we pass in here, that is okay since the cache will
// be invalidated upon the next read.
func (c *Cache) MaybeWriteBackToCache(

Maybe add a comment about how the entrySize should be calculated?

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pkg/sql/syntheticprivilegecache/cache.go line 298 at r1 (raw file):

}

func computePrivDescSize(privDesc *catpb.PrivilegeDescriptor) int64 {

Could we add a comment for this as well?

[rafiss]

1. The bound account need to increase the size by the sum of the key's and value's size
2. For a descriptor, its size should include those for the users.

Is it correct?

that's right. check out this example: https://go.dev/play/p/liBjF3Jetk5?v=goprev
it shows that unsafe.Sizeof only shows the length of the string header, and the actual bytes of the string need to be counted separately.

bors r=ZhouXing19

Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @ZhouXing19)

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pkg/sql/cacheutil/cache.go line 85 at r1 (raw file):

Previously, ZhouXing19 (Jane Xing) wrote…

Maybe add a comment about how the entrySize should be calculated?

done

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pkg/sql/syntheticprivilegecache/cache.go line 298 at r1 (raw file):

Previously, ZhouXing19 (Jane Xing) wrote…

Could we add a comment for this as well?

done

[craig]

Build succeeded:

• Bazel Essential CI (Cockroach)