[tarantool-patches] Re: [PATCH v3 3/3] Lua: implement json path access to tuple fields
Vladimir Davydov
vdavydov.dev at gmail.com
Mon Apr 16 11:35:49 MSK 2018
On Sat, Apr 14, 2018 at 12:51:30AM +0300, Vladislav Shpilevoy wrote:
> Hello. Thanks for review.
>
> New commit message:
>
> lua: implement json path access to tuple fields
>
> Until this moment in Lua a tuple data could be accessed in 3 ways:
> - get field by field number, decode into Lua,
> - get field by field name, decode into Lua
> - decode entire tuple into Lua.
>
> It was impossible to decode into Lua only a part of the field to
> avoid Lua garbage creating. For example, consider the tuple:
> `{1, 2, {key1 = value1,
> key2 = {key21 = {key211 = {key2111, key2112}}}}}`
> with field names `field1`, `field2`, `field3`.
>
> To get `key2112` it is necessary to decode into Lua the entire
> 3-th field, including `key1`, `value1`, `key2`, `key21`,
> `key211`, `key2111` using the syntax
> `key2112 = tuple.field3.key2.key21.key211[2]`.
>
> Now the one can use the following syntax:
> `key2112 = tuple["field3.key2.key21.key211[2]"]`. The difference
> is in placing all the path into quotes and brackets `["..."]`.
> The Tarantool goes through this path and MessagePack tuple body,
> gets the needed tuple part and decodes into Lua only it.
>
> The path must be valid JSON path with one exception - in
> Tarantool a path can start with `.`. For example:
> `tuple[".field3..."]` - it is done to lay emphasis that the JSON
> path here is just a suffix for the tuple.
>
> At the same time tuple field names still work: `tuple["field1"]`,
> `tuple.field2`.
>
> If the field name looks like JSON path, for example:
> `my.field.name`, then it works too. The path at first is checked
> to be a real JSON path, and if nothing is found, then the entire
> path is considered as a field name. To combine such names and
> path elements the one can use `["..."]`. For example:
> `tuple["['my.field.name'].key1.key2.['another.key.in.map']"]`.
>
> Closes #1285
>
> >
> > Why did you move handling of integer index from Lua to C? AFAIU having
> > it in Lua should be faster. Besides, this new function is kinda
> > difficult to follow IMO as it does two things now. I'd prefer it to do
> > just one thing - looking up a tuple field by path.
> >
>
> Fixed. I returned the tuple field by number implementation as it
> was before JSON path patch.
Thanks. The patch looks good to me now.
There's one thing: the hunk below doesn't belong to this patch.
Obviously, it should be a part of the previous patch. Please move
it there before pushing it to the trunk.
diff --git a/test/unit/json_path.result b/test/unit/json_path.result
index 9b4ea641..a2a2f829 100644
--- a/test/unit/json_path.result
+++ b/test/unit/json_path.result
@@ -1,7 +1,7 @@
*** main ***
1..2
*** test_basic ***
- 1..67
+ 1..71
ok 1 - parse <[0]>
ok 2 - <[0]> is num
ok 3 - <[0]> is 0
@@ -46,29 +46,33 @@
ok 42 - <field1> is str
ok 43 - len is 6
ok 44 - str is field1
- ok 45 - parse <[1234]>
- ok 46 - <[1234]> is num
- ok 47 - <[1234]> is 1234
- ok 48 - parse empty path
- ok 49 - is str
- ok 50 - parse <field1>
- ok 51 - <field1> is str
- ok 52 - len is 6
- ok 53 - str is field1
- ok 54 - parse <[2]>
- ok 55 - <[2]> is num
- ok 56 - <[2]> is 2
- ok 57 - parse <[6]>
- ok 58 - <[6]> is num
- ok 59 - <[6]> is 6
- ok 60 - parse <привет中国world>
- ok 61 - <привет中国world> is str
- ok 62 - len is 23
- ok 63 - str is привет中国world
- ok 64 - parse <中国a>
- ok 65 - <中国a> is str
- ok 66 - len is 7
- ok 67 - str is 中国a
+ ok 45 - parse <field1>
+ ok 46 - <field1> is str
+ ok 47 - len is 6
+ ok 48 - str is field1
+ ok 49 - parse <[1234]>
+ ok 50 - <[1234]> is num
+ ok 51 - <[1234]> is 1234
+ ok 52 - parse empty path
+ ok 53 - is str
+ ok 54 - parse <field1>
+ ok 55 - <field1> is str
+ ok 56 - len is 6
+ ok 57 - str is field1
+ ok 58 - parse <[2]>
+ ok 59 - <[2]> is num
+ ok 60 - <[2]> is 2
+ ok 61 - parse <[6]>
+ ok 62 - <[6]> is num
+ ok 63 - <[6]> is 6
+ ok 64 - parse <привет中国world>
+ ok 65 - <привет中国world> is str
+ ok 66 - len is 23
+ ok 67 - str is привет中国world
+ ok 68 - parse <中国a>
+ ok 69 - <中国a> is str
+ ok 70 - len is 7
+ ok 71 - str is 中国a
ok 1 - subtests
*** test_basic: done ***
*** test_errors ***
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