Elektra
0.8.22
|
The Directory Value plugin converts
A directory value is a key that contains children. For example in the key set:
the keys
represent directory values, while the keys
specify leaf values. You can easily check this by drawing the key set in the form of a rooted tree:
. The Directory Value plugin converts all directory values to leaf values in the “set” direction by adding new keys with the postfix ___dirdata
. Theses keys then store the old value of their parent keys
. You might ask why we need the Directory Value plugin at all. The reason why we created this plugin is that some storage plugins like `yajl` or `yamlcpp` are only able to save values inside leaf keys. By loading the Directory Value plugin these storage plugins are also able to represent directory values properly.
The Directory value plugin also converts array values. Let us take a look at an example key set:
. The plugin does not convert this key set into:
, since then user/array
would not be an array any more. Instead the plugin inserts a new element at index 0 with the value prefix ___dirdata:
:
. This way a storage plugin such as YAJL or YAML CPP are still able to store user/array
as an array.
Remark: The plugin only converts array parents that store string values.
To mount the plugin use the command:
`` <h1>Mount plugin to cascading namespace
/examples/directoryvalue` sudo kdb mount config.file /examples/directoryvalue directoryvalue
sudo kdb umount /examples/directoryvalue
/examples/directoryvalue
sudo kdb mount config.file /examples/directoryvalue directoryvalue
kdb set /examples/directoryvalue/harold 'Father of SpongeBob SquarePants'
kdb set /examples/directoryvalue/harold/spongebob 'I am ready!'
kdb set /examples/directoryvalue/patrick Star kdb set /examples/directoryvalue/patrick/#0 'Being grown-up is boring. Besides, I don’t get Jazz.'
kdb ls /examples/directoryvalue #> user/examples/directoryvalue/harold #> user/examples/directoryvalue/harold/spongebob #> user/examples/directoryvalue/patrick #> user/examples/directoryvalue/patrick/#0
kdb get /examples/directoryvalue/harold #> Father of SpongeBob SquarePants kdb get /examples/directoryvalue/harold/spongebob #> I am ready!
kdb get /examples/directoryvalue/patrick #> Star kdb get /examples/directoryvalue/patrick/#0 #> Being grown-up is boring. Besides, I don’t get Jazz.
kdb getmeta /examples/directoryvalue/patrick array #> #0
kdb rm -r /examples/directoryvalue sudo kdb umount /examples/directoryvalue ```
Escaping is currently not possible. If you use the Directory Value plugin you can not
___dirdata
as the last part of a normal key,___dirdata:
at the beginning of a normal value in the first array element!