DEV: update examples on two JSON pages

[dwdougherty]

DOC-5003

@LiorKogan:

I've updated the return values from each example on the two modified pages using the latest available Redis Stack Docker image. What I can't work out is how the values stack. For example, in the following sequence of commands,

127.0.0.1:6379> JSON.SET arr . '[""]'
OK
127.0.0.1:6379> JSON.DEBUG MEMORY arr
(integer) 64

the size, if I believe the current write-up, should be 8 + 8 = 16 bytes. But, inexplicably, it's 64 bytes. I don't know how that result is calculated. So, I'll need your help with the sizing explanations in the content/develop/data-types/json/ram.md document.

[github-actions]

Staging links:
https://redis.io/docs/staging/DOC-5003/commands/json.debug-memory/
https://redis.io/docs/staging/DOC-5003/develop/data-types/json/ram

[LiorKogan]

@eranhd can you help here?

[ephraimfeldblum]

@dwdougherty no, it could not be 8 + 8.

The size of an empty array is 8 because it consists only of a pointer to a static "null" array. if it is non-empty, we need to store the additional metadata info (size, capacity) which is 16 more bytes.

Why it's 64 and not 32, I'll investigate. (Although it might just be as simple as the array having extra unused capacity.)

[ephraimfeldblum]

Yes, the array is created with default capacity 4. I did not investigate why. That leaves us with 56 bytes of used memory.

The additional 8 bytes comes from, as far as I can tell, a mistaken double counting of the string. It is being counted once when accounting for the used capacity of the array, and being counted again when recursively counting the memory consumed by the values stored in the array.

@LiorKogan @eranhd this should probably be fixed.

[ephraimfeldblum]

The expected behavior should be

127.0.0.1:6379> json.set a . '["", ""]'
OK
127.0.0.1:6379> json.debug memory a
(integer) 56
127.0.0.1:6379> json.set a . '["", "", ""]'
OK
127.0.0.1:6379> json.debug memory a
(integer) 56
127.0.0.1:6379> json.set a . '["", "", "", ""]'
OK
127.0.0.1:6379> json.debug memory a
(integer) 56
127.0.0.1:6379> json.set a . '["", "", "", "", ""]'
OK
127.0.0.1:6379> json.debug memory a
(integer) 88