Atomicity (ACID): Update operators
Don't do this:
r = db.steps.findOne( { 'person' : 'derickr' } );
*r['steps_made']["20140202"] = r['steps_made']["20140202"] + 7124;*
*db.steps.update( { 'person' : 'derickr' }, r );*
Do this instead:
db.steps.update(
{ 'person' : 'derickr' },
{ '$inc' : { "steps_made.20140202" : 7124 } }
);
Other operators:
db.steps.update(
{ 'person' : 'derickr' },
{ '$addToSet' : { 'tags' : 'openstreetmap' } }
);
db.steps.update(
{ 'person' : 'derickr' },
{ '$push' : { 'tags' : {
'$each' : [ 'mongodb', 'xdebug' ],
'$slice' : -2
} } }
);