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moved docs to new docs folder. updated tutorial for version 1.0.0

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Tony Hannan 2011-07-08 22:17:44 -04:00
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README.md
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mongoDB This is the Haskell MongoDB driver (client). [MongoDB](http://www.mongodb.org) is a free, scalable, fast, document database management system. This driver lets you connect to a MongoDB server, and update and query its data. It also lets you do adminstrative tasks, like create an index or look at performance statistics.
-------
About ### Documentation
----- * [Quick example](http://github.com/TonyGen/mongoDB-haskell/blob/master/doc/Example.hs)
* [Tutorial](http://github.com/TonyGen/mongoDB-haskell/blob/master/doc/tutorial.md)
MongoDB driver for Haskell, which lets you connect to a MongoDB database management system and do inserts, queries, updates, etc. * [Driver API](http://hackage.haskell.org/package/mongoDB)
* [MapReduce example](http://github.com/TonyGen/mongoDB-haskell/blob/master/doc/map-reduce-example.md)
Links * [Driver design](http://github.com/TonyGen/mongoDB-haskell/blob/master/doc/design.md)
----- * [MongoDB DBMS](http://www.mongodb.org)
* [MongoDB](http://www.mongodb.org)
* [mongoDB API reference](http://hackage.haskell.org/package/mongoDB)
* [tutorial](http://github.com/TonyGen/mongoDB-haskell/blob/master/tutorial.md)
* [map/reduce example](http://github.com/TonyGen/mongoDB-haskell/blob/master/map-reduce-example.md)

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docs/Example.hs Normal file
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{-# LANGUAGE OverloadedStrings #-}
import Database.MongoDB
import Control.Monad.Trans (liftIO)
main = do
pipe <- runIOE $ connect (host "127.0.0.1")
e <- access pipe master "baseball" run
close pipe
print e
run = do
clearTeams
insertTeams
printDocs "All Teams" =<< allTeams
printDocs "National League Teams" =<< nationalLeagueTeams
printDocs "New York Teams" =<< newYorkTeams
clearTeams = delete (select [] "team")
insertTeams = insertMany "team" [
["name" =: u"Yankees", "home" =: ["city" =: u"New York", "state" =: u"NY"], "league" =: u"American"],
["name" =: u"Mets", "home" =: ["city" =: u"New York", "state" =: u"NY"], "league" =: u"National"],
["name" =: u"Phillies", "home" =: ["city" =: u"Philadelphia", "state" =: u"PA"], "league" =: u"National"],
["name" =: u"Red Sox", "home" =: ["city" =: u"Boston", "state" =: u"MA"], "league" =: u"American"] ]
allTeams = rest =<< find (select [] "team") {sort = ["home.city" =: (1 :: Int)]}
nationalLeagueTeams = rest =<< find (select ["league" =: u"National"] "team")
newYorkTeams = rest =<< find (select ["home.state" =: u"NY"] "team") {project = ["name" =: (1 :: Int), "league" =: (1 :: Int)]}
printDocs title docs = liftIO $ putStrLn title >> mapM_ (print . exclude ["_id"]) docs

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V0.6-Redesign.md → docs/V0.6-Redesign.md
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This tutorial takes you through inserting, updating, and querying documents.
### Getting Ready
Start a local MongoDB server in a separate terminal window:
$ mkdir mongoFiles
$ mongod --dbpath mongoFiles
Start a haskell session:
$ ghci
Import the MongoDB driver library, and set OverloadedStrings so literal strings are converted to UTF-8 automatically.
> :set -XOverloadedStrings
> import Database.MongoDB
### Connecting
Establish a connection to your local Mongo server on the standard port (27017):
> pipe <- runIOE $ connect $ host "127.0.0.1"
A host with non-standard port would look like `Host "127.0.0.1" (PortNumber 27001)`.
`connect h` has type `ErrorT IOError IO Pipe`. `runIOE` brings this type back down to `IO Pipe` and throws the IOError in IO if present. One design principle of this driver was to make DB errors explicit, hence the need for `runIOE`.
A `Pipe` is a thread-safe, pipelined (a' la [HTTP pipelining](http://en.wikipedia.org/wiki/HTTP_pipelining)) TCP connection to a MongoDB server. Multiple threads can use the pipe at the same time. The pipelining feature is used by cursors and not exposed to the user.
### Action monad
A DB read or write operation is called a DB `Action`. A DB Action is a monad so you can sequence them together. To run an Action supply it to the `access` function with the Pipe to read/write to, the `AccessMode` for read/write operations, and the `Database` to access. For example, to list all collections in the "test" database:
> access pipe master "test" allCollections
`access` return either Left `Failure` or Right result. Failure means there was a connection failure, or a read/write failure like cursor expired or duplicate key insert.
`master` is an `AccessMode`. Access mode indicates how reads and writes will be performed. Its three modes are: `ReadStaleOk`, `UnconfirmedWrites`, and `ConfirmWrites GetLastErrorParams`. `master` is just short hand for `ConfirmWrites []`. The first mode may be used against a slave or a master server, the last two must be used against a master server.
Since we are working in ghci, which requires us to start from the IO monad every time, we'll define a convenient *run* function that takes an action and executes it against our "test" database on the server we just connected to, with master access mode:
> let run = access pipe master "test"
### Databases and Collections
To see all the databases available on the server:
> run allDatabases
The "test" database in context is ignored in this case because `allDatabases` is not a query on a specific database but on the server as a whole.
Databases and collections do not need to be created, just start using them and MongoDB will automatically create them for you. In the examples below we'll be using the "test" database (captured in *run* above) and the "posts" colllection.
### Documents
Data in MongoDB is represented (and stored) using JSON-style documents, called BSON documents. A `Document` is simply a list of `Field`s, where each field is a label-value pair. A `Value` is a basic type like Bool, Int, Float, String, Time; a special BSON value like Binary, Javascript, ObjectId; a (embedded) Document; or a list of Values. Here's an example document which could represent a blog post:
> let post = ["author" =: "Mike", "text" =: "My first blog post!", "tags" =: ["mongoDB", "Haskell"]]
### Inserting One
To insert a document into a collection we can use the `insert` function.
> run $ insert "posts" post
When a document is inserted and it does not contain an *_id* field then it is added with a globally unique value of type `ObjectId`. The *_id* value can be any type but must be unique across the collection. `insert` returns the *_id* value of the inserted document.
After inserting the first document, the "posts" collection has actually been created on the server. We can verify this by listing all of the collections in our database again:
> run allCollections
Note, the "system.indexes" collection is a special internal collection that was created automatically.
### Reading One
The most basic type of query that can be performed in MongoDB is `findOne`. This function returns a single document matching the selection, or `Nothing` if there are no matches. It is useful when you know there is only one matching document, or are only interested in the first match. Here we use `findOne` to get the first document from the posts
collection:
> run $ findOne $ select [] "posts"
The result is a document matching the one that we inserted previously. Note, the returned document contains the _id field, which was automatically added on insert.
`findOne` also supports querying on specific elements that the resulting document must match. For example, to limit our results to a document with author "Mike" we do:
> run $ findOne $ select ["author" =: "Mike"] "posts"
If we try with a different author, like "Eliot", we'll get no result:
> run $ findOne $ select ["author" =: "Eliot"] "posts"
`fetch` is the same as `findOne` except it fails if no document matches.
### Inserting Many
In order to make querying a little more interesting, let's insert a few more documents. In addition to inserting a single document, we can also perform bulk insert operations, by using the `insertMany` function which accepts a list of documents to be inserted. It sends only a single write operation to the server.
> let post1 = ["author" =: "Mike", "text" =: "Another post!", "tags" =: ["bulk", "insert"]]
> let post2 = ["author" =: "Eliot", "title" =: "MongoDB is fun", "text" =: "and pretty easy too!"]
> run $ insertMany "posts" [post1, post2]
Note that *post2* has a different shape than the other posts; it has no "tags" field and a new "title" field. Documents in the same collection can have different schemas.
### Reading Many
To retrieve more than a single document we use the `find` function. `find` returns a `Cursor`, which allows us to
iterate over the matching documents. There are few ways in which we can iterate: `next` gets the documents one at a time, and `rest` gets all (remaining) documents in the query result.
> run $ find (select ["author" =: "Mike"] "posts") >>= rest
`next` automatically closes the cursor when the last document has been read out of it, similarly for `rest`. Otherwise, you should close a cursor if you don't exhaust it via `closeCursor`.
### Counting
You can count how many documents are in an entire collection:
> run $ count $ select [] "posts"
Or count how many documents match a query:
> run $ count $ select ["title" =: ["$exits" =: True]] "posts"
### Sorting
`sort` takes the fields to sort by and whether ascending (1) or descending (-1)
> run $ find (select [] "posts") {sort = ["author" =: 1, "title" =: 1]} >> rest
If you don't sort, documents are returned in *natural* order, which is the order found on disk. Natural order is not particularly useful because, although the order is often close to insertion order, it is not guaranteed.
### Projecting
`project` returns partial documents containing only the fields you include (1). However, *_id* is always included unless you exclude it (0).
> run $ find (select [] "posts") {project = ["author" =: 1, "_id" =: 0]}
### Updating
`save` updates an existing document
> run $ fetch (select ["author" =: "Eliot"] "posts") >>= save "posts" . merge ["tags" =: ["hello"]]
or inserts a new document if its *_id* is new or missing
> run $ save "posts" ["author" =: "Tony", "text" =: "Haskell rocks"]
`modify` updates every document matching selection according to supplied modifier. For example:
> run $ modify (select [] "posts") ["$push" =: ["tags" =: "new"]]
### Deleting
`delete` deletes all documents matching selection. `deleteOne` deletes one document matching selection (the first one in *natural* order), if any
> run $ delete $ select ["author" =: "Homer"] "posts" -- none deleted in this case
### Documentation
Documentation on the Mongo query language, i.e. the selector document, modifier document, etc., can be found at the [MongoDB Developer Zone](http://www.mongodb.org/display/DOCS/Developer+Zone).
Haddock generated documentation on this Haskell driver can be found on [Hackage](http://hackage.haskell.org/package/mongoDB).

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mongoDB.cabal
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@ -22,8 +22,8 @@ stability: alpha
homepage: http://github.com/TonyGen/mongoDB-haskell homepage: http://github.com/TonyGen/mongoDB-haskell
package-url: package-url:
bug-reports: bug-reports:
synopsis: MongoDB driver synopsis: Driver (client) for MongoDB, a free, scalable, fast, document database management system
description: This module lets you connect to MongoDB (www.mongodb.org) and do inserts, queries, updates, etc. Please see the example in Database.MongoDB and the tutorial from the homepage. description: This package lets you connect to MongoDB servers and update/query their data. Please see the example in Database.MongoDB and the tutorial from the homepage. For information about MongoDB itself, see www.mongodb.org.
category: Database category: Database
author: Tony Hannan <tony@10gen.com> & Scott Parish <srp@srparish.net> author: Tony Hannan <tony@10gen.com> & Scott Parish <srp@srparish.net>
tested-with: tested-with:

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tutorial.md
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MongoDB Haskell Mini Tutorial
-----------------------------
__Updated:__ Oct 2010
This is a mini tutorial to get you up and going with the basics
of the Haskell mongoDB drivers. You will need the mongoDB driver
installed as well as mongo itself. Prompts used in this tutorial are:
$ = command line prompt
> = ghci repl prompt
Installing Haskell Bindings
---------------------------
From Hackage using cabal:
$ cabal install mongoDB
From Source:
$ git clone git://github.com/TonyGen/mongoDB-haskell.git mongoDB
$ cd mongoDB
$ runhaskell Setup.hs configure
$ runhaskell Setup.hs build
$ runhaskell Setup.hs install
Getting Ready
-------------
Start a MongoDB instance for us to play with in a separate terminal window:
$ mongod --dbpath <directory where Mongo will store the data>
Start up a haskell repl:
$ ghci
Import the MongoDB driver library, and set
OverloadedStrings so literal strings are converted to UTF-8 automatically.
> import Database.MongoDB
> import Data.CompactString ()
> :set -XOverloadedStrings
Making A Connection
-------------------
Create a connection pool for your mongo server, using the standard port (27017):
> pool <- newConnPool 1 $ host "127.0.0.1"
or for a non-standard port
> pool <- newConnPool 1 $ Host "127.0.0.1" (PortNumber 30000)
*newConnPool* takes the connection pool size, and the host to connect to. It returns
a *ConnPool*, which is a potential pool of TCP connections. They are not created until first
access, so it is not possible to get a connection error here.
Note, plain IO code in this driver never raises an exception unless it invokes third party IO
code that does. Driver code that may throw an exception says so in its Monad type,
for example, *ErrorT IOError IO a*.
Access monad
-------------------
A query/update executes in an *Access* monad, which has access to a
*Pipe*, *WriteMode*, and read-mode (*MasterSlaveOk*), and may throw a *Failure*.
A Pipe is a single TCP connection.
To run an Access action (monad), supply WriteMode, MasterOrSlaveOk, Connection,
and action to *access*. For example, to get a list of all the database on the server:
> access safe Master pool allDatabases
*access* return either Left Failure or Right result. Failure means there was a connection failure
or a read or write exception like cursor expired or duplicate key insert.
Since we are working in ghci, which requires us to start from the
IO monad every time, we'll define a convenient *run* function that takes an
action and executes it against our "test" database on the server we
just connected to, with typical write and read mode:
> let run action = access safe Master pool $ use (Database "test") action
*use* adds a *Database* to the action context, so query/update operations know which
database to operate on.
Databases and Collections
-----------------------------
MongoDB can store multiple databases -- separate namespaces
under which collections reside.
As before, you can obtain the list of databases available on a connection:
> run allDatabases
The "test" database in context is ignored in this case because *allDatabases*
is not a query on a specific database but on the server as a whole.
Databases and collections do not need to be created, just start using
them and MongoDB will automatically create them for you. In the below examples
we'll be using the database "test" (captured in *run* above) and the colllection "posts".
You can obtain a list of all collections in the "test" database:
> run allCollections
Documents
---------
Data in MongoDB is represented (and stored) using JSON-style
documents, called BSON documents. A *Document" is simply a list of *Field*s,
where each field is a named value. A *Value" is a basic type like Bool, Int, Float, String, Time;
a special BSON value like Binary, Javascript, ObjectId; a (embedded)
Document; or a list of values. Here's an example document which could
represent a blog post:
> import Data.Time
> now <- getCurrentTime
> :{
let post = ["author" =: "Mike",
"text" =: "My first blog post!",
"tags" =: ["mongoDB", "Haskell"],
"date" =: now]
:}
Inserting a Document
-------------------
To insert a document into a collection we can use the *insert* function:
> run $ insert "posts" post
When a document is inserted a special field, *_id*, is automatically
added if the document doesn't already contain that field. The value
of *_id* must be unique across the collection. *insert* returns the
value of *_id* for the inserted document. For more information, see
the [documentation on _id](http://www.mongodb.org/display/DOCS/Object+IDs).
After inserting the first document, the posts collection has actually
been created on the server. We can verify this by listing all of the
collections in our database:
> run allCollections
Note, the system.indexes collection is a special internal collection
that was created automatically.
Getting a single document with findOne
-------------------------------------
The most basic type of query that can be performed in MongoDB is
*findOne*. This method returns a single document matching a query (or
*Nothing* if there are no matches). It is useful when you know there is
only one matching document, or are only interested in the first
match. Here we use *findOne* to get the first document from the posts
collection:
> run $ findOne (select [] "posts")
The result is a document matching the one that we inserted previously.
Note, the returned document contains the *_id* field, which was automatically
added on insert.
*findOne* also supports querying on specific elements that the
resulting document must match. To limit our results to a document with
author "Mike" we do:
> run $ findOne (select ["author" =: "Mike"] "posts")
If we try with a different author, like "Eliot", we'll get no result:
> run $ findOne (select ["author" =: "Eliot"] "posts")
Bulk Inserts
------------
In order to make querying a little more interesting, let's insert a
few more documents. In addition to inserting a single document, we can
also perform bulk insert operations, by using the *insertMany* function
which accepts a list of documents to be inserted. It send only a single
command to the server:
> now <- getCurrentTime
> :{
let post1 = ["author" =: "Mike",
"text" =: "Another post!",
"tags" =: ["bulk", "insert"],
"date" =: now]
:}
> :{
let post2 = ["author" =: "Eliot",
"title" =: "MongoDB is fun",
"text" =: "and pretty easy too!",
"date" =: now]
:}
> run $ insertMany "posts" [post1, post2]
* Note that post2 has a different shape than the other posts - there
is no "tags" field and we've added a new field, "title". This is what we
mean when we say that MongoDB is schema-free.
Querying for More Than One Document
------------------------------------
To get more than a single document as the result of a query we use the
*find* method. *find* returns a *Cursor*, which allows us to
iterate over all matching documents. There are several ways in which
we can iterate: we can call *next* to get documents one at a time
or we can get all the results by applying the cursor to *rest*:
> Right cursor <- run $ find (select ["author" =: "Mike"] "posts")
> run $ rest cursor
Of course you can use bind (*>>=*) to combine these into one line:
> run $ find (select ["author" =: "Mike"] "posts") >>= rest
Note, *next* automatically closes the cursor when the last
document has been read out of it. Similarly, *rest* automatically
closes the cursor after returning all the results.
Counting
--------
We can count how many documents are in an entire collection:
> run $ count (select [] "posts")
Or count how many documents match a query:
> run $ count (select ["author" =: "Mike"] "posts")
Advanced Queries
-------------
To do
Indexing
--------
To do