How to delete documents by query efficiently in mongo?

Question

I have a query, which selects documents to be removed. Right now, I remove them manually, like this (using python): ``` for id in mycoll.find(query, fields={}): mycoll.remove(id) ``` This does not seem to be very efficient. Is there a better way? EDIT OK, I owe an apology for forgetting to mention the query details, because it matters. Here is the complete python code: ``` def reduce_duplicates(mydb, max_group_size): # 1. Count the group sizes res = mydb.static.map_reduce(jstrMeasureGroupMap, jstrMeasureGroupReduce, 'filter_scratch', full_response = True) # 2. For each entry from the filter scratch collection having count > max_group_size deleteFindArgs = {'fields': {}, 'sort': [('test_date', ASCENDING)]} for entry in mydb.filter_scratch.find({'value': {'$gt': max_group_size}}): key = entry['_id'] group_size = int(entry['value']) # 2b. query the original collection by the entry key, order it by test_date ascending, limit to the group size minus max_group_size. for id in mydb.static.fi…

Accepted Answer

You can use a query to remove all matching documents

```
var query = {name: 'John'};
db.collection.remove(query);
```

Be wary, though, if number of matching documents is high, your database might get less responsive. It is often advised to delete documents in smaller chunks.

Let's say, you have 100k documents to delete from a collection. It is better to execute 100 queries that delete 1k documents each than 1 query that deletes all 100k documents.

How to delete documents by query efficiently in mongo?

Solution

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