chickadee » sublevel

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sublevel

Description

Provides easy namespacing of keys inside a single LevelDB database. This is an implementation of the level API.

Example use

(use level leveldb sublevel lazy-seq)

(define db (open-db "./my-database"))

(define books (sublevel db '("books")))
(define cds (sublevel db '("music" "cds")))

(db-put books "book1" "foo")
(db-put books "book2" "bar")

(lazy-seq->list (db-pairs books)) ;; => (("book1" "foo") ("book2" "bar"))
(lazy-seq->list (db-pairs cds)) ;; => ()

API

sublevel db prefixprocedure

Wraps a level implementation with namespaced access. Keys are generated by joining name space strings with the null character.

expand-sublevels root db opsprocedure

Takes a list of operations (as you would pass to the db-batch procedure) and expands the keys in the list to match the full key that would be written for the provdided sublevel(s). The key namespaces between 'root' and 'db' are expanded. The 'root' argument can be any level implementation (eg, a raw leveldb object or another sublevel).

This can be useful if you find yourself needing to apply a transaction across multiple sublevels. You can use this for each sublevel to build the final batch operations list then use db-batch on the underlying resource.

;; Example
(define db (open-db "./my-database"))
(define sub1 (sublevel db '("one")))
(define sub2 (sublevel sub1 '("two")))

(expand-sublevels db sub2 '((put "example" "value")))
;; => '((put "one\x00two\x00example" "value"))

(expand-sublevels sub1 sub2 '((put "example" "value")))
;; => '((put "two\x00example" "value"))

Source code / issues

https://github.com/caolan/chicken-sublevel

Changelog

4.0.0

• update to latest level egg api (v3.0.0)

3.0.0

• update to latest level egg api (v2.0.0)

2.0.0

• expand-sublevels now requires a 'root' argument to expand up until (backwards incompatible change) - this is to make sure it can be safely used by libraries operating inside external sublevels

1.1.0

• added expand-sublevels procedure
• now using records for underlying sublevel resources