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Liam McLennan hackingon.net

I have a MongoDb collection called tweets. Each document has a property system_classification. If the value of system_classification is ‘+’ I want to change it to ‘positive’.

For a regular relational database the query would be:

update tweets
set system_classification = 'positive'
where system_classification = '+'

the MongoDb equivalent is:

 db.tweets.update({system_classification: '+'}, 
 {$set: {system_classification:'positive'}}, false, true)

Parameter Description

{ system_classification: '+' }

the first parameter identifies the documents to select

{ $set: { system_classification: 'positive' } }

the second parameter is an operation ($set) and the parameter to that operation {system_classification: ‘positive’}
false the third parameter indicates if this is a regular update or an upsert (true for upsert)
true the final parameter indicates if the operation should be applied to all selected documents (or just the first)
Posted on Tuesday, June 1, 2010 7:15 PM | Back to top

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