Question

This is a sample document holding OHLC stock data, truncated (via python print).

{
   "_id":ObjectId("4f1c567d60de7d0908000000"),
   "ticker" : "msft"
   "pricing":[
      {
         "Volume":"2094300",
         "Adj Close":"85.87",
         "High":"88.11",
         "Low":"87.45",
         "Date":         ISODate("2011-01-14T00:00:00         Z"),
         "Close":"88.10",
         "Open":"87.74"
      },
      {
         "Volume":"2351900",
         "Adj Close":"85.81",
         "High":"88.87",
         "Low":"87.76",
         "Date":         ISODate("2011-01-13T00:00:00         Z"),
         "Close":"88.04",
         "Open":"88.47"
      },
      {
         "Volume":"2732900",
         "Adj Close":"86.42",
         "High":"88.76",
         "Low":"87.92",
         "Date":         ISODate("2011-01-12T00:00:00         Z"),
         "Close":"88.66",
         "Open":"88.02"
      }

Couple questions about this:

1. Is there any way to index things within a document and not within a collection? I want to be able to easily look up data by date, maybe there is a better way to organize the data?

2. I am confused as to how to retrieve or update a specific pricing data, I tried to push in the new pricing data using:

   var = collection.find({ ‘ticker’ : ticker}) //Find the correct document

   var[0].update( { ‘$push’ : { ‘pricing’ : newpricingdata } }) //update that companies values

but it doesnt work. Find works fine, update doesnt.

newpricingdata looks like (python print):

[
   {
      'Volume':'3522600',
      'Adj Close':'85.65',
      'High':'85.70',
      'Low':'84.96',
      'Date':datetime.datetime(2012,1,20,0,0),
      'Close':'85.65',
      'Open':'85.45'
   },
   {
      'Volume':'3413700',
      'Adj Close':'85.80',
      'High':'86.23',
      'Low':'84.92',
      'Date':datetime.datetime(2012,1,19,0,0),
      'Close':'85.80',
      'Open':'85.10'
   },

]

1. How would you retrieve the price of ticker msft on say 1/20/2012 via python? The mongodb documentation doesnt really give good examples of subtree operations…

Answer 1

If you want to query by date then:

collection.ensureIndex({"pricing.Date" : 1}) 

To update pricing data, you have to call the update() method on collection, just as you call find() on the same collection, and you want $pushAll since newpricingdata is an array:

collection.update({ "_id" : ObjectId("4f1c567d60de7d0908000000")}, { '$pushAll' : { 'pricing' : newpricingdata } }, false, false); 

Question:

How would you retrieve the price of ticker msft on say 1/20/2012 via
python? The mongodb documentation doesnt really give good examples of
subtree operations…

It’s not possible to query and return only matching elements of an array, mongodb will give you the whole array. Which means you’ll have to extract that element in python.