Norbert, I have to come back to your answer. With the .explain option, I can see, how performance is with and without index on the _mongo console_. As an example, I see: with index only 2 objects scanned, without: 200. Performance is perfect with index. But _from smalltalk_, it seems to iterate over all objects, also with the index set. Slow. You wrote: "The index will be selected automatically." It seems that it does not. My question: MongoQuery has an attribute named "where" which is filled with the mentioned "receipts.receiptDescription". Because of the name of this attribute "where" and the slow performance, I assume that the mongo classes use the $where command: http://docs.mongodb.org/manual/reference/operator/query/where/ Is this right? In this case with the statement Trip selectMany: { 'receipts.receiptDescription' -> 'Tankquittung' } asDictionary the index would not be set automatically. "The $where provides greater flexibility, but requires that the database processes the JavaScript expression or function for each document in the collection. " Then my question is if the mongo classes support database queries with index and if yes, how. I am very interested in your opinion and I think other users should have the same requirements (querying indexed variables) - how did they solve this? Regards Sabine 2015-08-04 14:47 GMT+02:00 Sabine Manaa <manaa.sabine@gmail.com>:
Hi Norbert,
I didn't want to use "use database" for queries but for defining the
index from within smalltalk. But if creating indexes is not supported, I will set the indexes within the mongo console.
The explain option is very helpful I did not know this.
Your answer was very helpful for me, thanks a lot! Sabine
2015-08-04 10:42 GMT+02:00 NorbertHartl [via Smalltalk] <[hidden email]>:
Sabine,
Am 04.08.2015 um 07:08 schrieb Sabine Manaa <[hidden email]>:
Hi,
I have 2 questions concerning use of mongoDB classes: 1) how can I send mongo console commands directly from smalltalk 2) how to query on an embedded collection with an index
Model: I have trips and each trip has an embedded collection of N receipts like this: { "tripName" : "trip 1", {"receipts" : [ {"receiptDescription" : "receipt 1" } {"receiptDescription" : "receipt 2" } {"receiptDescription" : "receipt 3" } ], }
Index: For quick search, I created an index on the embeded[1] receipts with this command at the mongoDB console in a terminal (NOT in smalltalk) (mongo console starts with mongo in the MongoDB/bin dir):
db.Trips.createIndex({"receipts.receiptDescription":1})
with a command like this in the mongoDB console
db.Trips.find({"receipts.receiptDescription":"receipt 1"})
I get the resulting receipt.
Before, I have to set the database with "use {databasename}" in thr
mongodb
console
My questions: 1) how can I send mongo console commands directly from smalltalk, e.g. use database, set index etc.
I don't know why you want to use "use database". For queries you don't need this because you choose the database and collection by using the smalltalk classes. You can look there if something you need exists. Creating indexes is not yet supported. I want to do that myself. As always there seems to be to less people implementing stuff like that.
Is this possible? I did not succeed with the mongo command: method, it always returns "no such cmd".
2) how can I search for a receipt which is indexed as described from smalltalk?
A simple
Trip selectMany: { 'receipts.receiptDescription' -> 'Tankquittung' } asDictionary
should do. You can use just the nested properties form. The index will be selected automatically. If you are not sure about queries read about explain [1] to optimize that stuff.
[1] http://docs.mongodb.org/manual/reference/method/cursor.explain/#cursor.expla...
Norbert
I did not succeed with the description [2] I am not sure if it is covered by it.
Regards Sabine
[1]
http://docs.mongodb.org/manual/core/index-multikey/#index-arrays-with-embedd...
[2] http://smallworks.eu/web/blog/2013-07-18-Voyage-advanced-queries
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