How to find last update/insert/delete operation time on mongodb collection without objectid field

问题

I have some unused collections in the MongoDb database. I've to find out when the CRUD operations done against collections in the database. We have our own _id field instead of mongo's default object_id. We dont have any time filed in the collections to find out the modification time. is there any way to find out the modification time of collections in mongodb from meta data? Is there any data dictionay informations like in oracle to find out this? please give some idea/workarounds

回答1:

To make a long story short: MongoDB has a flexible schema. Simply add a date field. Since older entries don't have it, they can not be the last entry.

Let's call that field mtime.

So after adding a date field to your schema definition, we generate an index in descending order on the new field:

db.yourCollction.createIndex({mtime:-1})

Finding the last mtime for a collection now is easy:

db.yourCollection.find({"mtime":{"$exists":true}}).sort({"mtime":-1}).limit(1)

Do this for every collection. When the above query does not return a value within the timeframe you defined for purging a collection, simply drop it, since it has not been modified since you introduced the mtime field.

After your collections are cleaned up, you may remove the mtime field from your schema definition. To remove it from the documents, you can run a simple query:

db.yourCollection.update(
  { "mtime":{ $exists:true} },
  { "$unset":{ "mtime":""} },
  { multi: true}
)

回答2:

There is no "data dictionary" to get this information in MongoDB.

If you've enabled the profiling level in advance to log all operations (db.setProfilingLevel(2)) and you haven't had many operations to log, so that the system.profile capped collection hasn't overwritten whatever logs you are interested in, you can get the information you need there—but otherwise it's gone.

来源：https://stackoverflow.com/questions/33383612/how-to-find-last-update-insert-delete-operation-time-on-mongodb-collection-witho

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mongodb

collections