Saturday, 5 May 2012

Mongo get started - notes to self

Installing MongoDB on a mac

Download from
Download for your O/S - I am on a mac - so mongodb-osx-x86_64-2.0.4.tgz
Go to the directory beneath which you want to install mongo.
tar xvzf mongodb-osx-x86_64-2.0.4.tgz
Create a soft link mongo to the versioned directory so that you can support upgrades seamlessly ie
ln -s mongodb-osx-x86_64-2.0.4 mongo

Pentaho loading into MongoDB

Loading data into mongodb using Pentaho Kettle (PDI)

MongoDB commands/tips

It's up to the client to determine the type of the field in a document.
Note - it's possible to have different types in the same field in different documents in the same collection!

At a glance MongoDB commands

> help                    help on db methods             help on collection methods                    help on replica set methods
show dbs                     show database names
show collections             show collections in current database
show users                   show users in current database
show profile                 show most recent system.profile entries with time >= 1ms
show logs                    show the accessible logger names
show log [name]              prints out the last segment of log in memory, 'global' is default
use                set current database                list objects in collection foo { a : 1 } )     list objects in foo where a == 1
it                           result of the last line evaluated; use to further iterate
DBQuery.shellBatchSize = x   set default number of items to display on shell
exit                         quit the mongo shell

>                     count items in collection foo

More commands here from the site

Query Dates

Find a record which has today's date between eff_from_dt (effective_from date) and eff_to_date (effective_to date)

> db.test.findOne({eff_from_dt: { $lte: new Date() }, eff_to_dt: { $gte: new Date() }} )
        "_id" : ObjectId("50892120c2e69e0d395d6daa"),
        "field1" : "129384749",
        "field2" : "ABC",
        "field3" : "XYZ",
        "eff_from_dt" : ISODate("2012-05-14T23:00:00Z"),
        "eff_to_dt" : ISODate("9999-12-31T00:00:00Z")

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