> Am 07.08.2015 um 14:53 schrieb Sabine Manaa <manaa.sab...@gmail.com>:
>
> Hi Norbert, Hi Phil,
>
> thanks for your help! Now I know what the problem is/was. :-)))
>
> The query was right, the index was used, all is fine.
>
> BUT:
> I used an inspector to look at the query's result and opening the inspector
> forced to load all the other objects which belong to the object found.
> Explanation: I have a person which has N trips with N receipts, all with back
> pointers. Opening an Inspector with one trip loads its person and all other
> trips of this person hahaha. The magritte description isLazy but the
> inspector forced the loading of the objects in the VOMongoRepository at first
> time after image starting.
>
> Time millisecondsToRun: [(RKATrip selectMany: { 'receipts.receiptDescription'
> -> 'a' } asDictionary) size] 764 .
> Time millisecondsToRun: [(RKATrip selectMany: { 'receipts.receiptDescription'
> -> 'a' } asDictionary) inspect] 17234
>
> So, I messed around with myself.
>
Well, we call this an inversed Heisenbug, don't we? :) That is a problem we
should be aware when using proxy implementations and tools like gt tools. It is
very likely that a powerful tool will inquire special information on a proxy
that will trigger it.
> Currently I do not have so much data but I hope in future there will be a lot
> and I want the application prepared for that.
>
It depends on the tool and your model. Are you storing those backreferences in
mongo as well?
Norbert
> BTW: I found this nice document:
> https://ci.inria.fr/pharo-contribution/job/EnterprisePharoBook/ws/Voyage/Voyage.pdf
>
> <https://ci.inria.fr/pharo-contribution/job/EnterprisePharoBook/ws/Voyage/Voyage.pdf>
> I was mentioned there, thanks! Esteban, if you want, you could change my
> name, I married and changed my name to Manaa.
>
> have a nice weekend
> Sabine
>
> 2015-08-06 15:36 GMT+02:00 NorbertHartl [via Smalltalk] <[hidden email]
> <x-msg://13/user/SendEmail.jtp?type=node&node=4841464&i=0>>:
> Sabine,
>
>> Am 06.08.2015 um 14:49 schrieb Sabine Manaa <[hidden email]
>> <http://user/SendEmail.jtp?type=node&node=4841238&i=0>>:
>>
>> 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.
>>
>
> Usually it does.
>
>> 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/
>> <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?
>>
> The handling of indexes needs to be automatic. The rule of thumb is that if
> you use where clause like b = , c = , a= than you need an compound index in
> the same order being index(b,c,a). This is handled by the database when it
> analyzes the query it tries to find an appropriate index. Or seeing it from
> the other side: If you issue a query with index and the index does not fit
> the query it is a problem anyway. Are you sure you have only this one thing
> in the where query?
>
> I use e.g.
>
> COInstalledApp selectOne: {
> 'device.id <http://device.id/>' -> aString.
> 'application.__id' -> anApplication voyageId } asDictionary
>
> on a collection that has approx. 1 Mio. entires and it is fast. I didn't
> check with explain but I'll do if I find time :)
>
> If I were you I would step in the debugger down to the Voyage part after
> serialization. Then you have the exact Dictionary that is used to send to
> mongo. You can then use this query to do an "explain" on it and that should
> show you something. Another thing you can try (although I don't think makes
> any difference) is to use the non-javascript query variant. That would be
>
> Trip selectMany: {
> 'receipts' -> {
> 'receiptDescription' -> 'Tankquittung' } asDictionary }
> asDictionary
>
> Norbert
>
>> Regards
>> Sabine
>>
>>
>> 2015-08-04 14:47 GMT+02:00 Sabine Manaa <[hidden email]
>> <http://user/SendEmail.jtp?type=node&node=4841238&i=1>>:
>>
>> >
>> > 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.explain
>> >>
>> >> <http://docs.mongodb.org/manual/reference/method/cursor.explain/#cursor.explain>
>> >>
>> >> 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-embedded-documents
>> >>
>> >> <http://docs.mongodb.org/manual/core/index-multikey/#index-arrays-with-embedded-documents>
>> >> [2] http://smallworks.eu/web/blog/2013-07-18-Voyage-advanced-queries
>> >> <http://smallworks.eu/web/blog/2013-07-18-Voyage-advanced-queries>
>> >>
>> >>
>> >>
>> >> --
>> >> View this message in context:
>> >> http://forum.world.st/MongoDB-console-commands-query-embedded-indexed-fields-tp4840882.html
>> >>
>> >> <http://forum.world.st/MongoDB-console-commands-query-embedded-indexed-fields-tp4840882.html>
>> >> Sent from the Pharo Smalltalk Users mailing list archive at Nabble.com
>> >> <http://nabble.com/>.
>> >>
>> >>
>> >>
>> >>
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>> >
>> >
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