Count number of collection per given list of dates and documents using Mongo shell

Question

I have following collections in Mongo DB:

AAA-01-Nov-2019
AAA-02-Nov-2019
AAA-03-Nov-2019
AAA-04-Nov-2019
AAA-05-Nov-2019
AAA-06-Nov-2019
AAA-07-Nov-2019
AAA-08-Nov-2019
AAA-09-Nov-2019
BBB-01-Nov-2019
BBB-02-Nov-2019
BBB-03-Nov-2019
BBB-04-Nov-2019
BBB-05-Nov-2019
BBB-06-Nov-2019
BBB-07-Nov-2019
BBB-08-Nov-2019
BBB-09-Nov-2019

I also have a list of dates:

my_dates = ["01-Nov-2019", "03-Nov-2019", "05-Nov-2019", "01-Jan-2020"]

I want to:

count number of documents in collections AAA and BBB only for dates in my_dates
be notified if date from my_dates does not have collection AAA or BBB (can be just count = 0 or text that particular collection do not exists).
count number of AAA's and BBB's to clearly see that it is equal to len(my_dates) (because len(my_dates) can be over 100).

I stacked with be able to count number of documents for collections that starts with AAA or BBB like this:

db.getCollectionNames().forEach(function(collection) 
{
  if(collection.startsWith("AAA") || collection.startsWith("BBB"))
  {
    resultCount = db[collection].count();
    print("Results count for " + collection + ":\t"+ resultCount);
    }
  });

Adding date to collection name can be done like this:

if(collection.startsWith("AAA"+"-01-Oct-2019"))

but I do not know how to iterate it with elements from my_dates.

Valijon · Accepted Answer · 2020-01-31 15:07:33Z

0

Take a look if this solution meets your requirements:

You may iterate my_dates array with .forEach method or with for operator:

for(var i=0; i<my_dates.length; i++) {
    print(my_dates[i])
}

MongoDB provides method exists which checks if collection is created (can be empty collection):

var my_dates    = ["01-Nov-2019", "03-Nov-2019", "05-Nov-2019", "01-Jan-2020"];
my_dates.forEach(function(date){
    ["AAA", "BBB"].forEach(function(prefix){
        var col = prefix + "-" + date;
        //Check if exists
        if(db.getCollection(col).exists() !=null){
            print("Results count for " + col + ":\t"+ db.getCollection(col).count());    
        } else {
            //Not exists
            print("Results count for " + col + ":\t"+ "-1");
        }
    });
});

answered Jan 31, 2020 at 15:07

Valijon

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2 Comments

Piotrek Leśniak Over a year ago

Second solution hangs in my intellishell.

Valijon Over a year ago

@Piotrek It hangs probably because .count() takes too much time. Try to modfy the script and not count total values

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