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MongoDB ObjectId generator/parser for Common Lisp

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README.markdown

cl-mongo-id

This is a simple library for creating/handling MongoDB's ObjectIDs. It works by grabbing key pieces of info (unix timestamp, hostname, process pid, global "inc" value) and creating a new ObjectID as a 12-byte array #(79 151 129 ...)

It aims to be as cross-platform/implementation as possible. If you find you're unable to run it on your specific platform, please let me know and I'll do whatever I can to fix it!

Usage

Install

(ql:quickload :cl-mongo-id)

Create byte array from string id:

(mongoid:oid "4f9638d834322b9531000005")  ->
    #(79 150 56 216 52 50 43 149 49 0 0 5)

Create new id using MongoDB ObjectID specification:

(mongoid:oid)  ->
    #(79 150 62 92 61 196 44 20 228 0 0 0)

Grab a string representation of an ObjectID:

(mongid:oid-str (mongoid:oid))  ->
    "4F97001C3DC42C14E4000050"

Usage with cl-mongo

The cl-mongo-id library can be used with cl-mongo. There is just one caveat: You must import the make-bson-oid function from the cl-mongo package before you can use the two together.

(import 'cl-mongo::make-bson-oid)

(with-mongo-connection (:host "127.0.0.1" :db "test")
  ;; querying a document of a known id
  (db.find "mycoll" (kv "_id" (make-bson-oid :oid (mongoid:oid "4f9638d834322b9531000005"))))

  ;; creating a new document with an oid
  (let ((doc (make-document :oid (make-bson-oid :oid (mongoid:oid)))))
    (db.save "mycoll" doc)))

Thread safe

cl-mongo-id is built to be thread-safe (specifically the inc value). This means you can create ID's via (oid) from several different threads without problems, and your inc value will be unique between all of them.

Helper functions

cl-mongo-id has some helper functions that may be useful to you for either debugging or grabbing values from your IDs.

Note that all of the following helper functions take a keyword argument :bytes, which if set to T will return the raw bytes of that portion of the ID and not convert them to an integer.

get-timestamp

Get the unix timestamp from a Mongo Object ID:

(mongoid:get-timestamp (oid "4f96f9fa3dc42c14e400004e"))  ->
    1335294458

get-pid

Get the PID the ID was created under:

(mongoid:get-pid (oid "4f96f9fa3dc42c14e400004e"))  ->
    5348

get-hostname

Get the int value corresponding to the first three bytes of the MD5 of the hostname the ID was created on:

(mongoid:get-hostname (oid "4f96f9fa3dc42c14e400004e"))  ->
    4047916
(mongoid:get-hostname (oid "4f96f9fa3dc42c14e400004e") :bytes t)  ->
    #(61 196 44)

get-inc

Get the ID's "inc" value:

(mongoid:get-inc (oid "4f96f9fa3dc42c14e400004e"))  ->
    78
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