date:20140417


Am 17.04.2014 um 10:08 schrieb Olivier Auverlot olivier.auver...@gmail.com:

 Hi,
 
 I'm using Voyage and I need to duplicate an existing document in a Mongo 
 database. I suppose that the id must be changed before saving.
 
 What is the best way to do that ?
 
If you need a shallow copy then you better just copy the object and store it. 
Changing the id is asking for trouble I guess. That would probably work if you 
implement #= on those objects but I think it is a hack.

anObject copy save

should do.

Norbert

Re: [Pharo-users] how to duplicate document with Voyage


On 17 Apr 2014, at 10:17, Norbert Hartl norb...@hartl.name wrote:

 
 Am 17.04.2014 um 10:08 schrieb Olivier Auverlot olivier.auver...@gmail.com:
 
 Hi,
 
 I'm using Voyage and I need to duplicate an existing document in a Mongo 
 database. I suppose that the id must be changed before saving.
 
 What is the best way to do that ?
 
 If you need a shallow copy then you better just copy the object and store it. 
 Changing the id is asking for trouble I guess. That would probably work if 
 you implement #= on those objects but I think it is a hack.
 
 anObject copy save

+1

 
 should do.
 
 Norbert

Re: [Pharo-users] how to duplicate document with Voyage

2014-04-17 Thread olivier auverlot

simply ? Thanks ;-)


2014-04-17 10:42 GMT+02:00 Esteban Lorenzano esteba...@gmail.com:


 On 17 Apr 2014, at 10:17, Norbert Hartl norb...@hartl.name wrote:

 
  Am 17.04.2014 um 10:08 schrieb Olivier Auverlot 
 olivier.auver...@gmail.com:
 
  Hi,
 
  I'm using Voyage and I need to duplicate an existing document in a
 Mongo database. I suppose that the id must be changed before saving.
 
  What is the best way to do that ?
 
  If you need a shallow copy then you better just copy the object and
 store it. Changing the id is asking for trouble I guess. That would
 probably work if you implement #= on those objects but I think it is a hack.
 
  anObject copy save

 +1

 
  should do.
 
  Norbert

Re: [Pharo-users] RDBMS Atomic Counter?

2014-04-17 Thread itli...@schrievkrom.de

I think this is simply a case of optimistic locking - there is a general
way and very often db specific ways

first you get the current active value ... (one row)

currentValue from select counterfield from tablename


then you update the table (single row)


update
  tablename
set
  counterfield = currentValue + 1
where
  counterfield = currentValue

commit

then you look how many rows have been changed (=1) and assume, that
commit was successful and then you know if you were successful ...
otherwise you must retry ...

this is a simple, with worst performance but portale approach ...

Marten


Am 16.04.2014 21:52, schrieb Esteban A. Maringolo:
 Hi,
 
 A few weeks ago Sven was asking for a lock-free in-image atomic counter.
 
 Today I'm in need of implementing a DB backed (PGSQL) counter for
 business forms numbering, and maybe there are some toughts you're
 willing to share :)
 
 I can't find any other way than a row lock for each counter, but maybe
 there is something better (I avoid locks as much as possible).
 
 Any thoughts to share here?
 
 Regards!
 


-- 
Marten Feldtmann

[Pharo-users] Voyage: how to delete references to objects.

2014-04-17 Thread olivier

Hi,

I'm using Voyage in a Pharo application.

I have two MongoDB collections which are ComicsCollection and ComicsBook. Each 
book is attached to a instance of ComicsCollection. The reference of each book 
is stored in an ordered collection (in the instance of ComicsCollection). The 
problem is that if I remove a book, the reference to the book is not deleted 
from ComicsCollection.

How can I remove properly a book and the reference to the book ?

Best regards
Olivier ;-)

Re: [Pharo-users] Voyage: how to delete references to objects.


Am 17.04.2014 um 13:53 schrieb olivier olivier.auver...@gmail.com:

 Hi,
 
 I'm using Voyage in a Pharo application.
 
 I have two MongoDB collections which are ComicsCollection and ComicsBook. 
 Each book is attached to a instance of ComicsCollection. The reference of 
 each book is stored in an ordered collection (in the instance of 
 ComicsCollection). The problem is that if I remove a book, the reference to 
 the book is not deleted from ComicsCollection.
 
 How can I remove properly a book and the reference to the book ?
 
From the smalltalk image view the problem is usually exactly the opposite: You 
don’t delete objects but you remove references to them. As voyage maps objects 
it is a good idea to stay in the object realm. So you should rather remove the 
book from the collection. This way you won’t get errors just garbage. The 
„real“ problem that arises then is that the book would still be in the 
database. Just like it is in the image but there is no garbage collector for 
mongo. To decide that from the image is not possible. You load only a sub graph 
from the database into image memory. So you don’t know if there are other 
objects referencing the book.

If your records fit all in memory you could load all collections and books and 
build the difference between all referenced books in the collections and the 
total amount of books. The difference will be the set of objects not being 
referenced by a collection and those can be deleted.

If the records do not fit in memory an alternative strategy would be needed. I 
started to research if it is possible to build a map/reduce based garbage 
collector for common cases but got distracted. But I have the same problem so I 
will need to pick it up some time.

hope that helps,

Norbert

Re: [Pharo-users] Voyage: how to delete references to objects.


Am 17.04.2014 um 15:05 schrieb olivier auverlot olivier.auver...@gmail.com:

 thanks Robert for the explications.
 
It’s Norbert btw. :)

 I agree with you that's the best way to remove a book is to delete the 
 reference in  ComicsCollection.
 
 But how to do that ? Must I simply remove the reference in the ordered 
 collection ? Voyage will syncronize automatically the data in memory with the 
 content of the database ? Must I force the save of the data after removing 
 the reference ?
 
You need to explicitly save it as we don’t have something like write barriers 
in the image. So

aComicCollection 
removeBook: aBook;
save

is needed.

Norbert

 Olivier ;-)
 
 
 2014-04-17 14:10 GMT+02:00 Norbert Hartl norb...@hartl.name:
 
 Am 17.04.2014 um 13:53 schrieb olivier olivier.auver...@gmail.com:
 
  Hi,
 
  I'm using Voyage in a Pharo application.
 
  I have two MongoDB collections which are ComicsCollection and ComicsBook. 
  Each book is attached to a instance of ComicsCollection. The reference of 
  each book is stored in an ordered collection (in the instance of 
  ComicsCollection). The problem is that if I remove a book, the reference to 
  the book is not deleted from ComicsCollection.
 
  How can I remove properly a book and the reference to the book ?
 
 From the smalltalk image view the problem is usually exactly the opposite: 
 You don’t delete objects but you remove references to them. As voyage maps 
 objects it is a good idea to stay in the object realm. So you should rather 
 remove the book from the collection. This way you won’t get errors just 
 garbage. The „real“ problem that arises then is that the book would still be 
 in the database. Just like it is in the image but there is no garbage 
 collector for mongo. To decide that from the image is not possible. You load 
 only a sub graph from the database into image memory. So you don’t know if 
 there are other objects referencing the book.
 
 If your records fit all in memory you could load all collections and books 
 and build the difference between all referenced books in the collections and 
 the total amount of books. The difference will be the set of objects not 
 being referenced by a collection and those can be deleted.
 
 If the records do not fit in memory an alternative strategy would be needed. 
 I started to research if it is possible to build a map/reduce based garbage 
 collector for common cases but got distracted. But I have the same problem so 
 I will need to pick it up some time.
 
 hope that helps,
 
 Norbert

Re: [Pharo-users] Voyage: how to delete references to objects.

2014-04-17 Thread olivier auverlot

Norbert,

Sorry for my mistake ;-)



2014-04-17 15:18 GMT+02:00 Norbert Hartl norb...@hartl.name:


 Am 17.04.2014 um 15:05 schrieb olivier auverlot 
 olivier.auver...@gmail.com:

 thanks Robert for the explications.

 It’s Norbert btw. :)

 I agree with you that's the best way to remove a book is to delete the
 reference in  ComicsCollection.

 But how to do that ? Must I simply remove the reference in the ordered
 collection ? Voyage will syncronize automatically the data in memory with
 the content of the database ? Must I force the save of the data after
 removing the reference ?

 You need to explicitly save it as we don’t have something like write
 barriers in the image. So

 aComicCollection
 removeBook: aBook;
 save

 is needed.

 Norbert

 Olivier ;-)


 2014-04-17 14:10 GMT+02:00 Norbert Hartl norb...@hartl.name:


 Am 17.04.2014 um 13:53 schrieb olivier olivier.auver...@gmail.com:

  Hi,
 
  I'm using Voyage in a Pharo application.
 
  I have two MongoDB collections which are ComicsCollection and
 ComicsBook. Each book is attached to a instance of ComicsCollection. The
 reference of each book is stored in an ordered collection (in the instance
 of ComicsCollection). The problem is that if I remove a book, the reference
 to the book is not deleted from ComicsCollection.
 
  How can I remove properly a book and the reference to the book ?
 
 From the smalltalk image view the problem is usually exactly the
 opposite: You don’t delete objects but you remove references to them. As
 voyage maps objects it is a good idea to stay in the object realm. So you
 should rather remove the book from the collection. This way you won’t get
 errors just garbage. The „real“ problem that arises then is that the book
 would still be in the database. Just like it is in the image but there is
 no garbage collector for mongo. To decide that from the image is not
 possible. You load only a sub graph from the database into image memory. So
 you don’t know if there are other objects referencing the book.

 If your records fit all in memory you could load all collections and
 books and build the difference between all referenced books in the
 collections and the total amount of books. The difference will be the set
 of objects not being referenced by a collection and those can be deleted.

 If the records do not fit in memory an alternative strategy would be
 needed. I started to research if it is possible to build a map/reduce based
 garbage collector for common cases but got distracted. But I have the same
 problem so I will need to pick it up some time.

 hope that helps,

 Norbert

Re: [Pharo-users] Voyage: how to delete references to objects.

2014-04-17 Thread Sabine Knöfel

Hi Olivier,

possibly the option
VOMongoContainerenableMissingContent;
is useful to avoid
http://forum.world.st/Voyage-image-freeze-VOMongoError-Lazy-reference-not-found-td4703739.html

Here is an example:
http://esug.org/data/ESUG2013/4-Thu/03-ESUG2013%20-%20VoyageTutorial.pdf

Regards
Sabine

On Thu, Apr 17, 2014 at 3:07 PM, Olivier Auverlot [via Smalltalk]
ml-node+s1294792n4755092...@n4.nabble.com wrote:

thanks Robert for the explications.

I agree with you that's the best way to remove a book is to delete the
reference in ComicsCollection.

But how to do that ? Must I simply remove the reference in the ordered
collection ? Voyage will syncronize automatically the data in memory with
the content of the database ? Must I force the save of the data after
removing the reference ?

Olivier ;-)

2014-04-17 14:10 GMT+02:00 Norbert Hartl [hidden
email]http://user/SendEmail.jtp?type=nodenode=4755092i=0
:

Am 17.04.2014 um 13:53 schrieb olivier [hidden
email]http://user/SendEmail.jtp?type=nodenode=4755092i=1
:

Hi,

I'm using Voyage in a Pharo application.

I have two MongoDB collections which are ComicsCollection and
ComicsBook. Each book is attached to a instance of ComicsCollection. The
reference of each book is stored in an ordered collection (in the instance
of ComicsCollection). The problem is that if I remove a book, the reference
to the book is not deleted from ComicsCollection.

How can I remove properly a book and the reference to the book ?

From the smalltalk image view the problem is usually exactly the
opposite: You don’t delete objects but you remove references to them. As
voyage maps objects it is a good idea to stay in the object realm. So you
should rather remove the book from the collection. This way you won’t get
errors just garbage. The „real“ problem that arises then is that the book
would still be in the database. Just like it is in the image but there is
no garbage collector for mongo. To decide that from the image is not
possible. You load only a sub graph from the database into image memory. So
you don’t know if there are other objects referencing the book.

If your records fit all in memory you could load all collections and
books and build the difference between all referenced books in the
collections and the total amount of books. The difference will be the set
of objects not being referenced by a collection and those can be deleted.

If the records do not fit in memory an alternative strategy would be
needed. I started to research if it is possible to build a map/reduce based
garbage collector for common cases but got distracted. But I have the same
problem so I will need to pick it up some time.

hope that helps,

Norbert

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Re: [Pharo-users] Voyage: how to delete references to objects.

Sabine,

I read the case now the first time. Just one note. Having references in both
directions is probably not the best idea if using a non-object store. For
navigating the graph it might be good but for persisting it is not. The
serialization is a lot more complex if you do and the gain is nothing. For most
databases with proper indexes you can request both directions easily and fast.
So having one reference pointing from A to B you get the opposite direction for
free.

Norbert

Am 17.04.2014 um 15:22 schrieb Sabine Knöfel sabine.knoe...@gmail.com:

Hi Olivier,

possibly the option
VOMongoContainerenableMissingContent;
is useful to avoid
http://forum.world.st/Voyage-image-freeze-VOMongoError-Lazy-reference-not-found-td4703739.html

Here is an example:
http://esug.org/data/ESUG2013/4-Thu/03-ESUG2013%20-%20VoyageTutorial.pdf

Regards
Sabine

On Thu, Apr 17, 2014 at 3:07 PM, Olivier Auverlot [via Smalltalk] [hidden
email] wrote:
thanks Robert for the explications.

I agree with you that's the best way to remove a book is to delete the
reference in ComicsCollection.

But how to do that ? Must I simply remove the reference in the ordered
collection ? Voyage will syncronize automatically the data in memory with the
content of the database ? Must I force the save of the data after removing
the reference ?

Olivier ;-)

2014-04-17 14:10 GMT+02:00 Norbert Hartl [hidden email]:

Am 17.04.2014 um 13:53 schrieb olivier [hidden email]:

Hi,

I'm using Voyage in a Pharo application.

I have two MongoDB collections which are ComicsCollection and ComicsBook.
Each book is attached to a instance of ComicsCollection. The reference of
each book is stored in an ordered collection (in the instance of
ComicsCollection). The problem is that if I remove a book, the reference to
the book is not deleted from ComicsCollection.

How can I remove properly a book and the reference to the book ?

From the smalltalk image view the problem is usually exactly the opposite:
You don’t delete objects but you remove references to them. As voyage maps
objects it is a good idea to stay in the object realm. So you should rather
remove the book from the collection. This way you won’t get errors just
garbage. The „real“ problem that arises then is that the book would still be
in the database. Just like it is in the image but there is no garbage
collector for mongo. To decide that from the image is not possible. You load
only a sub graph from the database into image memory. So you don’t know if
there are other objects referencing the book.

If your records fit all in memory you could load all collections and books
and build the difference between all referenced books in the collections and
the total amount of books. The difference will be the set of objects not
being referenced by a collection and those can be deleted.

If the records do not fit in memory an alternative strategy would be needed.
I started to research if it is possible to build a map/reduce based garbage
collector for common cases but got distracted. But I have the same problem so
I will need to pick it up some time.

hope that helps,

Norbert

If you reply to this email, your message will be added to the discussion
below:
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To unsubscribe from Pharo Smalltalk Users, click here.
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Re: [Pharo-users] Voyage: how to delete references to objects.

2014-04-17 Thread Sabine Knöfel

Hi Norbert,

for me the gain within smalltalk is huge because I want to navigate from
person to trip and from trip to person by the attributes without asking
mongo for the correspondent object via indexes.

Don't you think that this is a question of design of the object model and
should not be decided by database arguments?

Regards
Sabine

On Thu, Apr 17, 2014 at 3:40 PM, NorbertHartl [via Smalltalk]
ml-node+s1294792n4755102...@n4.nabble.com wrote:

Sabine,

I read the case now the first time. Just one note. Having references in
both directions is probably not the best idea if using a non-object store.
For navigating the graph it might be good but for persisting it is not. The
serialization is a lot more complex if you do and the gain is nothing. For
most databases with proper indexes you can request both directions easily
and fast. So having one reference pointing from A to B you get the opposite
direction for free.

Norbert

Am 17.04.2014 um 15:22 schrieb Sabine Knöfel [hidden
email]http://user/SendEmail.jtp?type=nodenode=4755102i=0
:

Hi Olivier,

possibly the option
VOMongoContainerenableMissingContent;
is useful to avoid

http://forum.world.st/Voyage-image-freeze-VOMongoError-Lazy-reference-not-found-td4703739.html

Here is an example:
http://esug.org/data/ESUG2013/4-Thu/03-ESUG2013%20-%20VoyageTutorial.pdf

Regards
Sabine

On Thu, Apr 17, 2014 at 3:07 PM, Olivier Auverlot [via Smalltalk] a
href=x-msg://56/user/SendEmail.jtp?type=nodeamp;node=4755097amp;i=0
target=_top rel=nofollow link=external[hidden email] wrote:

thanks Robert for the explications.

I agree with you that's the best way to remove a book is to delete the
reference in ComicsCollection.

Olivier ;-)

2014-04-17 14:10 GMT+02:00 Norbert Hartl [hidden
email]http://user/SendEmail.jtp?type=nodenode=4755092i=0
:

Am 17.04.2014 um 13:53 schrieb olivier [hidden
email]http://user/SendEmail.jtp?type=nodenode=4755092i=1
:

Hi,

I'm using Voyage in a Pharo application.

How can I remove properly a book and the reference to the book ?

hope that helps,

Norbert

--
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Re: [Pharo-users] Voyage: how to delete references to objects.

Am 17.04.2014 um 15:52 schrieb Sabine Knöfel sabine.knoe...@gmail.com:

Hi Norbert,

for me the gain within smalltalk is huge because I want to navigate from
person to trip and from trip to person by the attributes without asking mongo
for the correspondent object via indexes.

Don't you think that this is a question of design of the object model and
should not be decided by database arguments?

I think there isn’t only one _or_ the other. Of course it is a lot more
beautiful to have set up proper objects and collections and do everything in a
smalltalkish way. That does only count as long as you stay on the island
(smalltalk image). As soon as you start to play with the outer world you have
to change your rules. If you agree it isn’t perfectly beautiful if you have a
proper object model that freezes your image, right? :)
IMHO the beauty comes from a mixture of both that fit them together without
restricting one or the other.

So I would try to avoid storing both directions. But which one to skip? If I
assume that a person can have a lot of trips than I would skip the collection
inside Person. The more trips a Person has the bigger the serialized document
becomes. This makes it first slower to operate on the database and will fail if
you reach a document size of 16MB because that is the maximum Mongo supports.
Most of the time this will be a non-issue but for now I take it into account.
So the data model will have a class Trip with an instVar pointing to Person.
And Person will have an instVar trips that is transient (see
VOMongoTransientDescription). The implementation for Person then goes

Person#trips
^ trips ifNil: [ trips := self fetchTrips ]

Person#fetchTrips
^ Trips selectMany: [: each| … ]

Person#addTrip: aTrip
aTrip person: self.
aTrip save

So the Trip will have a reference to Person in the database but Person will
have no reference to Trip. Person will retrieve its trips as soon as they are
used in a really smalltalkish way :). Person acts as a smalltalk object and as
a database object cache at the same time.
So this an implementation of Person that on the inside takes the database
nature in regard but on the outside the interface is pure smalltalk.

Still not good?

Norbert

Regards
Sabine

On Thu, Apr 17, 2014 at 3:40 PM, NorbertHartl [via Smalltalk] [hidden
email] wrote:
Sabine,

I read the case now the first time. Just one note. Having references in both
directions is probably not the best idea if using a non-object store. For
navigating the graph it might be good but for persisting it is not. The
serialization is a lot more complex if you do and the gain is nothing. For
most databases with proper indexes you can request both directions easily and
fast. So having one reference pointing from A to B you get the opposite
direction for free.

Norbert

Am 17.04.2014 um 15:22 schrieb Sabine Knöfel [hidden email]:

Hi Olivier,

possibly the option
VOMongoContainerenableMissingContent;
is useful to avoid
http://forum.world.st/Voyage-image-freeze-VOMongoError-Lazy-reference-not-found-td4703739.html

Here is an example:
http://esug.org/data/ESUG2013/4-Thu/03-ESUG2013%20-%20VoyageTutorial.pdf

Regards
Sabine

On Thu, Apr 17, 2014 at 3:07 PM, Olivier Auverlot [via Smalltalk] a
href=x-msg://56/user/SendEmail.jtp?type=nodeamp;node=4755097amp;i=0
target=_top rel=nofollow link=external[hidden email] wrote:
thanks Robert for the explications.

I agree with you that's the best way to remove a book is to delete the
reference in ComicsCollection.

Olivier ;-)

2014-04-17 14:10 GMT+02:00 Norbert Hartl [hidden email]:

Am 17.04.2014 um 13:53 schrieb olivier [hidden email]:

Hi,

I'm using Voyage in a Pharo application.

I have two MongoDB collections which are ComicsCollection and ComicsBook.
Each book is attached to a instance of ComicsCollection. The reference of
each book is stored in an ordered collection (in the instance of
ComicsCollection). The problem is that if I remove a book, the reference
to the book is not deleted from ComicsCollection.

How can I remove properly a book and the reference to the book ?

From the smalltalk image view the problem is usually exactly the opposite:
You don’t delete objects but you remove references to them. As voyage maps
objects it is a good idea to stay in the object realm. So you should rather
remove the book from the collection. This way you won’t get errors just
garbage. The „real“ problem that arises then is that the book would still be
in the database. Just like it is in the image but there is no garbage
collector for mongo. To decide that from the

Re: [Pharo-users] Voyage: how to delete references to objects.


On 17 Apr 2014, at 15:18, Norbert Hartl norb...@hartl.name wrote:

 
 Am 17.04.2014 um 15:05 schrieb olivier auverlot olivier.auver...@gmail.com:
 
 thanks Robert for the explications.
 
 It’s Norbert btw. :)
 
 I agree with you that's the best way to remove a book is to delete the 
 reference in  ComicsCollection.
 
 But how to do that ? Must I simply remove the reference in the ordered 
 collection ? Voyage will syncronize automatically the data in memory with 
 the content of the database ? Must I force the save of the data after 
 removing the reference ?
 
 You need to explicitly save it as we don’t have something like write barriers 
 in the image. So
 
 aComicCollection 
   removeBook: aBook;
   save
 
 is needed.

yes, and also (if you want to be clean):

aBook remove. 

(assuming aBook is also persistent). 

But as Sabina points: #enableMissingContent in CommicCollection will help you 
to simplify things, then you just need: aBook remove, and next time you read 
aComicCollection it will “clean” the invalid reference. 
I call that “eventual integrity” :P 
but beware of it… is considered “power voyage programming” :)

Esteban

 
 Norbert
 
 Olivier ;-)
 
 
 2014-04-17 14:10 GMT+02:00 Norbert Hartl norb...@hartl.name:
 
 Am 17.04.2014 um 13:53 schrieb olivier olivier.auver...@gmail.com:
 
  Hi,
 
  I'm using Voyage in a Pharo application.
 
  I have two MongoDB collections which are ComicsCollection and ComicsBook. 
  Each book is attached to a instance of ComicsCollection. The reference of 
  each book is stored in an ordered collection (in the instance of 
  ComicsCollection). The problem is that if I remove a book, the reference 
  to the book is not deleted from ComicsCollection.
 
  How can I remove properly a book and the reference to the book ?
 
 From the smalltalk image view the problem is usually exactly the opposite: 
 You don’t delete objects but you remove references to them. As voyage maps 
 objects it is a good idea to stay in the object realm. So you should rather 
 remove the book from the collection. This way you won’t get errors just 
 garbage. The „real“ problem that arises then is that the book would still be 
 in the database. Just like it is in the image but there is no garbage 
 collector for mongo. To decide that from the image is not possible. You load 
 only a sub graph from the database into image memory. So you don’t know if 
 there are other objects referencing the book.
 
 If your records fit all in memory you could load all collections and books 
 and build the difference between all referenced books in the collections and 
 the total amount of books. The difference will be the set of objects not 
 being referenced by a collection and those can be deleted.
 
 If the records do not fit in memory an alternative strategy would be needed. 
 I started to research if it is possible to build a map/reduce based garbage 
 collector for common cases but got distracted. But I have the same problem 
 so I will need to pick it up some time.
 
 hope that helps,
 
 Norbert

Re: [Pharo-users] Voyage: how to delete references to objects.

On 17 Apr 2014, at 16:26, Norbert Hartl norb...@hartl.name wrote:

Am 17.04.2014 um 15:52 schrieb Sabine Knöfel sabine.knoe...@gmail.com:

Hi Norbert,

for me the gain within smalltalk is huge because I want to navigate from
person to trip and from trip to person by the attributes without asking
mongo for the correspondent object via indexes.

Don't you think that this is a question of design of the object model and
should not be decided by database arguments?

I think there isn’t only one _or_ the other. Of course it is a lot more
beautiful to have set up proper objects and collections and do everything in
a smalltalkish way. That does only count as long as you stay on the island
(smalltalk image). As soon as you start to play with the outer world you have
to change your rules. If you agree it isn’t perfectly beautiful if you have a
proper object model that freezes your image, right? :)
IMHO the beauty comes from a mixture of both that fit them together without
restricting one or the other.

So I would try to avoid storing both directions. But which one to skip? If I
assume that a person can have a lot of trips than I would skip the collection
inside Person. The more trips a Person has the bigger the serialized document
becomes. This makes it first slower to operate on the database and will fail
if you reach a document size of 16MB because that is the maximum Mongo
supports. Most of the time this will be a non-issue but for now I take it
into account.
So the data model will have a class Trip with an instVar pointing to Person.
And Person will have an instVar trips that is transient (see
VOMongoTransientDescription). The implementation for Person then goes

Person#trips
^ trips ifNil: [ trips := self fetchTrips ]

Person#fetchTrips
^ Trips selectMany: [: each| … ]

Person#addTrip: aTrip
aTrip person: self.
aTrip save

So the Trip will have a reference to Person in the database but Person will
have no reference to Trip. Person will retrieve its trips as soon as they are
used in a really smalltalkish way :). Person acts as a smalltalk object and
as a database object cache at the same time.
So this an implementation of Person that on the inside takes the database
nature in regard but on the outside the interface is pure smalltalk.

Still not good?

yes, no good :)
I mean: I understand there are times when you need it, but I would prefer a
framework to solve that for me (then I can think just in my objects).
And if the framework does not do a good job, then is a bad framework (even if
made by me :P) and it needs to be improved.

having to think in persistence is a cancer that needs to be removed :P

Esteban

Norbert

Regards
Sabine

On Thu, Apr 17, 2014 at 3:40 PM, NorbertHartl [via Smalltalk] [hidden
email] wrote:
Sabine,

I read the case now the first time. Just one note. Having references in both
directions is probably not the best idea if using a non-object store. For
navigating the graph it might be good but for persisting it is not. The
serialization is a lot more complex if you do and the gain is nothing. For
most databases with proper indexes you can request both directions easily
and fast. So having one reference pointing from A to B you get the opposite
direction for free.

Norbert

Am 17.04.2014 um 15:22 schrieb Sabine Knöfel [hidden email]:

Hi Olivier,

possibly the option
VOMongoContainerenableMissingContent;
is useful to avoid
http://forum.world.st/Voyage-image-freeze-VOMongoError-Lazy-reference-not-found-td4703739.html

Here is an example:
http://esug.org/data/ESUG2013/4-Thu/03-ESUG2013%20-%20VoyageTutorial.pdf

Regards
Sabine

I agree with you that's the best way to remove a book is to delete the
reference in ComicsCollection.

Olivier ;-)

2014-04-17 14:10 GMT+02:00 Norbert Hartl [hidden email]:

Am 17.04.2014 um 13:53 schrieb olivier [hidden email]:

Hi,

I'm using Voyage in a Pharo application.

I have two MongoDB collections which are ComicsCollection and ComicsBook.
Each book is attached to a instance of ComicsCollection. The reference of
each book is stored in an ordered collection (in the instance of
ComicsCollection). The problem is that if I remove a book, the reference
to the book is not deleted from ComicsCollection.

How can I remove properly a book and the reference to the book ?

From the smalltalk image

Re: [Pharo-users] Voyage: how to delete references to objects.

Am 17.04.2014 um 18:05 schrieb Esteban Lorenzano esteba...@gmail.com:

On 17 Apr 2014, at 16:26, Norbert Hartl norb...@hartl.name wrote:

Am 17.04.2014 um 15:52 schrieb Sabine Knöfel sabine.knoe...@gmail.com:

Hi Norbert,

for me the gain within smalltalk is huge because I want to navigate from
person to trip and from trip to person by the attributes without asking
mongo for the correspondent object via indexes.

Don't you think that this is a question of design of the object model and
should not be decided by database arguments?

I think there isn’t only one _or_ the other. Of course it is a lot more
beautiful to have set up proper objects and collections and do everything in
a smalltalkish way. That does only count as long as you stay on the island
(smalltalk image). As soon as you start to play with the outer world you
have to change your rules. If you agree it isn’t perfectly beautiful if you
have a proper object model that freezes your image, right? :)
IMHO the beauty comes from a mixture of both that fit them together without
restricting one or the other.

So I would try to avoid storing both directions. But which one to skip? If I
assume that a person can have a lot of trips than I would skip the
collection inside Person. The more trips a Person has the bigger the
serialized document becomes. This makes it first slower to operate on the
database and will fail if you reach a document size of 16MB because that is
the maximum Mongo supports. Most of the time this will be a non-issue but
for now I take it into account.
So the data model will have a class Trip with an instVar pointing to Person.
And Person will have an instVar trips that is transient (see
VOMongoTransientDescription). The implementation for Person then goes

Person#trips
^ trips ifNil: [ trips := self fetchTrips ]

Person#fetchTrips
^ Trips selectMany: [: each| … ]

Person#addTrip: aTrip
aTrip person: self.
aTrip save

So the Trip will have a reference to Person in the database but Person will
have no reference to Trip. Person will retrieve its trips as soon as they
are used in a really smalltalkish way :). Person acts as a smalltalk object
and as a database object cache at the same time.
So this an implementation of Person that on the inside takes the database
nature in regard but on the outside the interface is pure smalltalk.

Still not good?

Sure. I was talking about _real_ stuff you can do _now_. I like to think just
in objects, too. But we have a separation in hard disc and memory so we need to
take care about persistence. I would also prefer to think just in programming
and not have to use a stupid device like a keyboard and a mouse just in order
to type silly characters that when interpreted probably come close to what I
meant. But for the time being I need to stick to it, I guess.

having to think in persistence is a cancer that needs to be removed :P

Yep, we just need a common memory space where we can waste Zetabytes of memory
to do little programs. Ah, and did I mention it needs to be infinitely fast
because I have a certain use case and I don’t like to optimize it because I
think that is cancer, too? Very academic view, well done! :)

Norbert

Esteban

Norbert

Regards
Sabine

On Thu, Apr 17, 2014 at 3:40 PM, NorbertHartl [via Smalltalk] [hidden
email] wrote:
Sabine,

I read the case now the first time. Just one note. Having references in
both directions is probably not the best idea if using a non-object store.
For navigating the graph it might be good but for persisting it is not. The
serialization is a lot more complex if you do and the gain is nothing. For
most databases with proper indexes you can request both directions easily
and fast. So having one reference pointing from A to B you get the opposite
direction for free.

Norbert

Am 17.04.2014 um 15:22 schrieb Sabine Knöfel [hidden email]:

Hi Olivier,

possibly the option
VOMongoContainerenableMissingContent;
is useful to avoid
http://forum.world.st/Voyage-image-freeze-VOMongoError-Lazy-reference-not-found-td4703739.html

Here is an example:
http://esug.org/data/ESUG2013/4-Thu/03-ESUG2013%20-%20VoyageTutorial.pdf

Regards
Sabine

I agree with you that's the best way to remove a book is to delete the
reference in ComicsCollection.

But how to do that ? Must I simply

Re: [Pharo-users] We need you for the upcoming Pharo's website

2014-04-17 Thread Damien Cassou

Hi Kilon,

On Wed, Apr 16, 2014 at 6:44 PM, kilon alios kilon.al...@gmail.com wrote:
 I was thinking of creating a screencast to explain in a few minutes why I
 like Pharo, emphasizing on live coding , the image and the development
 environment. By coincidence I recorded a test tutorial yesterday (before
 noticing this announcement) for the very basics of pharo, just 15 minutes.
 So its definitely  something I am willing to do. Its just that will like to
 do several tries and possible edit it to make it as efficient and as simple
 as possible.

 So If you are not in a hurry I can offer something.


that would be really great. We want to release the new website in the
coming 2/3 weeks, do you think you could make it? Maybe you could do
short ones that show a specific feature or two each? That would make
integration into the website easier. As an example, the ones of
babymock are great: http://www.youtube.com/watch?v=cPbItfNc5WY

Thanks

-- 
Damien Cassou
http://damiencassou.seasidehosting.st

Success is the ability to go from one failure to another without
losing enthusiasm.
Winston Churchill

Re: [Pharo-users] We need you for the upcoming Pharo's website


please use nice looking font and large ones and go ahead :)

On 16/4/14 18:44, kilon alios wrote:
I was thinking of creating a screencast to explain in a few minutes 
why I like Pharo, emphasizing on live coding , the image and the 
development environment. By coincidence I recorded a test tutorial 
yesterday (before noticing this announcement) for the very basics of 
pharo, just 15 minutes. So its definitely  something I am willing to 
do. Its just that will like to do several tries and possible edit it 
to make it as efficient and as simple as possible.


So If you are not in a hurry I can offer something.


On Wed, Apr 16, 2014 at 12:16 PM, Esteban Lorenzano 
esteba...@gmail.com mailto:esteba...@gmail.com wrote:


please do not answer all at once! (subtle irony)
anyway, I have to add that screencast has to be Pharo3 based.

cheers,
Esteban

On 15 Apr 2014, at 13:03, Damien Cassou damien.cas...@gmail.com
mailto:damien.cas...@gmail.com wrote:

 Hi everyone,

 we are working on a new website for Pharo! We need your help. If you
 have some time, please create and send us one of the following
items:

 - An up-to-date screenshot of Pharo 3.0 that shows some cool
features.
 It should be 800px wide ;
 - A screencast ;
 - A paragraph (around 40 words) that presents a nice topic about
Pharo
 and a corresponding screenshot.

 We will select 1 large screenshot, 3 screencasts and 4 topic
paragraphs.

 This could be a very nice way for you to contribute to Pharo!

 Best,

 --
 Damien Cassou
 http://damiencassou.seasidehosting.st

 Success is the ability to go from one failure to another without
 losing enthusiasm.
 Winston Churchill

Re: [Pharo-users] how to duplicate document with Voyage


Hi norbert

Olivier was doing a copy but it did not work and we thought that
Voyage should offer a clone or something like that that does not mess up 
with the id.

Because we already corrupted nicely a mongoDB.

Stef

On 17/4/14 10:17, Norbert Hartl wrote:

Am 17.04.2014 um 10:08 schrieb Olivier Auverlot olivier.auver...@gmail.com:


Hi,

I'm using Voyage and I need to duplicate an existing document in a Mongo 
database. I suppose that the id must be changed before saving.

What is the best way to do that ?


If you need a shallow copy then you better just copy the object and store it. 
Changing the id is asking for trouble I guess. That would probably work if you 
implement #= on those objects but I think it is a hack.

anObject copy save

should do.

Norbert

Re: [Pharo-users] how to duplicate document with Voyage


Ok so what I said was wrong :)

On 17/4/14 10:48, olivier auverlot wrote:

simply ? Thanks ;-)


2014-04-17 10:42 GMT+02:00 Esteban Lorenzano esteba...@gmail.com 
mailto:esteba...@gmail.com:



On 17 Apr 2014, at 10:17, Norbert Hartl norb...@hartl.name
mailto:norb...@hartl.name wrote:


 Am 17.04.2014 um 10:08 schrieb Olivier Auverlot
olivier.auver...@gmail.com mailto:olivier.auver...@gmail.com:

 Hi,

 I'm using Voyage and I need to duplicate an existing document
in a Mongo database. I suppose that the id must be changed before
saving.

 What is the best way to do that ?

 If you need a shallow copy then you better just copy the object
and store it. Changing the id is asking for trouble I guess. That
would probably work if you implement #= on those objects but I
think it is a hack.

 anObject copy save

+1


 should do.

 Norbert

Re: [Pharo-users] how to duplicate document with Voyage

Hi, 

copy should not mess with the id (unless your objects redefines = and hash).
I can take a look if Olivier is around tomorrow.

Esteban

On 17 Apr 2014, at 21:41, pharo4s...@free.fr wrote:

 Hi norbert
 
 Olivier was doing a copy but it did not work and we thought that
 Voyage should offer a clone or something like that that does not mess up with 
 the id.
 Because we already corrupted nicely a mongoDB.
 
 Stef
 
 On 17/4/14 10:17, Norbert Hartl wrote:
 Am 17.04.2014 um 10:08 schrieb Olivier Auverlot olivier.auver...@gmail.com:
 
 Hi,
 
 I'm using Voyage and I need to duplicate an existing document in a Mongo 
 database. I suppose that the id must be changed before saving.
 
 What is the best way to do that ?
 
 If you need a shallow copy then you better just copy the object and store 
 it. Changing the id is asking for trouble I guess. That would probably work 
 if you implement #= on those objects but I think it is a hack.
 
 anObject copy save
 
 should do.
 
 Norbert

Re: [Pharo-users] Voyage: how to delete references to objects.


esteban

you should do a pass on the voyage documentation chapter and add this 
kind of infomration.

We can pair write if you want.

stef

On 17/4/14 17:56, Esteban Lorenzano wrote:


On 17 Apr 2014, at 15:18, Norbert Hartl norb...@hartl.name 
mailto:norb...@hartl.name wrote:




Am 17.04.2014 um 15:05 schrieb olivier auverlot 
olivier.auver...@gmail.com mailto:olivier.auver...@gmail.com:



thanks Robert for the explications.


It’s Norbert btw. :)

I agree with you that's the best way to remove a book is to delete 
the reference in  ComicsCollection.


But how to do that ? Must I simply remove the reference in the 
ordered collection ? Voyage will syncronize automatically the data 
in memory with the content of the database ? Must I force the save 
of the data after removing the reference ?


You need to explicitly save it as we don’t have something like write 
barriers in the image. So


aComicCollection
removeBook: aBook;
save

is needed.


yes, and also (if you want to be clean):

aBook remove.

(assuming aBook is also persistent).

But as Sabina points: #enableMissingContent in CommicCollection will 
help you to simplify things, then you just need: aBook remove, and 
next time you read aComicCollection it will “clean” the invalid 
reference.

I call that “eventual integrity” :P
but beware of it… is considered “power voyage programming” :)

Esteban



Norbert


Olivier ;-)


2014-04-17 14:10 GMT+02:00 Norbert Hartl norb...@hartl.name 
mailto:norb...@hartl.name:



Am 17.04.2014 um 13:53 schrieb olivier
olivier.auver...@gmail.com mailto:olivier.auver...@gmail.com:

 Hi,

 I'm using Voyage in a Pharo application.

 I have two MongoDB collections which are ComicsCollection and
ComicsBook. Each book is attached to a instance of
ComicsCollection. The reference of each book is stored in an
ordered collection (in the instance of ComicsCollection). The
problem is that if I remove a book, the reference to the book is
not deleted from ComicsCollection.

 How can I remove properly a book and the reference to the book ?

From the smalltalk image view the problem is usually exactly the
opposite: You don’t delete objects but you remove references to
them. As voyage maps objects it is a good idea to stay in the
object realm. So you should rather remove the book from the
collection. This way you won’t get errors just garbage. The
„real“ problem that arises then is that the book would still be
in the database. Just like it is in the image but there is no
garbage collector for mongo. To decide that from the image is
not possible. You load only a sub graph from the database into
image memory. So you don’t know if there are other objects
referencing the book.

If your records fit all in memory you could load all collections
and books and build the difference between all referenced books
in the collections and the total amount of books. The difference
will be the set of objects not being referenced by a collection
and those can be deleted.

If the records do not fit in memory an alternative strategy
would be needed. I started to research if it is possible to
build a map/reduce based garbage collector for common cases but
got distracted. But I have the same problem so I will need to
pick it up some time.

hope that helps,

Norbert

Re: [Pharo-users] how to duplicate document with Voyage