This is a continuation of this question.
I'm using the following code to find all documents from collection C_a whose text contains the word StackOverflow and store them in another collection called C_b:
import pymongo from pymongo import MongoClient client = MongoClient('127.0.0.1') # mongodb running locally dbRead = client['C_a'] # using the test database in mongo # create the pipeline required pipeline = [{"$match": {"$text": {"$search":"StackOverflow"}}},{"$out":"C_b"}] # all attribute and operator need to quoted in pymongo dbRead.C_a.aggregate(pipeline) #execution print (dbRead.C_b.count()) ## verify count of the new collection This works great, however, if I run the same snippet for multiple keywords the results get overwritten. For example I want the collection C_b to contain all documents that contain the keywords StackOverflow, StackExchange, and Programming. To do so I simply iterate the snippet using the above keywords. But unfortunately, each iteration overwrites the previous.
Question: How do I update the output collection instead of overwriting it?
Plus: Is there a clever way to avoid duplicates, or do I have to check for duplicates afterwards?
1 Answers
Answers 1
If you look at the documentation $out doesn't support update
https://docs.mongodb.com/manual/reference/operator/aggregation/out/#pipe._S_out
So you need to do a two stage operation
pipeline = [{"$match": {"$text": {"$search":"StackOverflow"}}},{"$out":"temp"}] # all attribute and operator need to quoted in pymongo dbRead.C_a.aggregate(pipeline) and then use approach discussed in
https://stackoverflow.com/a/37433640/2830850
dbRead.C_b.insert( dbRead.temp.aggregate([]).toArray() ) And before starting the run you will need to drop the C_b collection
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