[tarantool-patches] Re: [PATCH v1 1/1] rfc: describe a Tarantool JSON indexes

Vladislav Shpilevoy v.shpilevoy at tarantool.org
Mon Jul 30 23:19:28 MSK 2018

Thanks for the fixes! Now I have no any major remark for
the RFC and the implementation method as well.

On 30/07/2018 22:23, Kirill Shcherbatov wrote:
> Actual link
> https://github.com/tarantool/tarantool/blob/db468f172e642d3d830018a20e545eff77c655e3/doc/rfc/1012-json-indexes.md
>> I still do not clearly understand what are you talking about. You can have
>> different offsets in the same path: 1) [1][2][3].field and 2) [1][2][3]["field"].
>> Here 'field' has offset 10 in the first case and 11 in the second
>> one.
>> If you want to use prefix length in off.cache on comparison to walk the
>> tuple_field trees along with the path in key_part on mismatch of cache
>> versions, then you should explain more clear how do you want to use
>> off.cache.
>> Lets suppose you have a key_part with a JSON path and a trees array.
>> To determine into which tree you first go to find offset_slot, you
>> should parse first path part. Same for each next part - you should
>> parse it to go down the tree. So you just do not know into which
>> tuple_field you go until the next part of the path is parsed. And how
>> does tuple_field.off_cache help here?
>> And what will you do when you met a format which does not have
>> an offset for the needed field? For example, I have created an
>> index, inserted multiple tuples, then created another index. The
>> format is changed, but the old tuples have the old format that
>> does not have an offset to the parts of the new index.
> You are right. This feature won't work.
>> As I said, it is not special index tree. It can describe a space
>> format with tens of fields among which only one is indexed.
>> Index_tree is not correct name. It is tuple_field array as it is
>> now, where each field is just a struct tuple_field. And struct
>> tuple_field can contain more tuple_fields inside either as an array
>> (if the field type is array) or inside a tree/hash if it is map.
> Ok, fixed.

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