Magma February 2008

magma@lists.squeakfoundation.org

9 participants
11 discussions

r41Beta1
by Chris Muller 04 Mar '08

04 Mar '08

I have just posted this new Monticello configuration to the "MagmaTester" project of squeaksource. I recommend using this for your development projects. This rolls up several fixes and enhancements including, most recently, a major improvement in single-clause query performance. #size and #at: are now handled in a single, brief, server call! This is the way it was in Magma years ago when single-clause was all that was supported, before #where: came along. Now, there are two subclasses of MagmaCollectionReader. MagmaCollectionFilteredReader and MagmaCollectionOptimizedReader. #where: will automatically determine whether your where: is a single clause and, if so, answer back the Optimized. The API is exactly the same, but Optimized will perform roughly 100X faster than Filtered with #size and #at:. This, of course, creates a need for conversion if you have persistent readers in your repository. They will have to be converted to an instance of either subclass, but that conversion script is not yet written. Enjoy, Chris

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Re: [squeak-dev] OmniBase/Magma - how big??
by goran＠krampe.se 02 Mar '08

02 Mar '08

Hi! (ccing Magma list) "Bill Schwab" <BSchwab(a)anest.ufl.edu> wrote: > Hello all, > > Any success or horror stories with OmniBase and/or Magma? Can you > report that either worked well at or got into trouble beyond any > particular size (either in object count or bytes of data)? Other > comments? > > Bill >From the Gjallar project we can report that Magma works really nice. We have had perhaps 2-3 buglets and Chris fixed them all quickly and promptly. IIRC they were related mainly to the query stuff which Chris pushed out fast because of our popular demand - so he was definitely not to blame. :) Generally I would say that the only "issue" we had was slow(ish) read performance. So if you write an "interactive" application with Magma you need to take two things into account: 1. Since Magma is an ODB it builds a cache of objects into your session. So when/if the session is cold you get punished with load times. But when it is hot they are zero. Essentially what this means in Gjallar is that when a user logs in things will take a bit of time the first time she does something. But from then on things go much faster and since a Gjallar user typically is logged in for a long time - typically all day - it works fine. 2. Even with a warm session (with lots of cached objects) you can still get punished with longish load times. This can be remedied a LOT with setting up good read strategies. IMHO I think Magma would SHINE if we somehow could boost the serialization/deserialization mechanism in it. Because I suspect this is where the bottleneck is regarding the above. An Exuperified Magma could be the answer - or some other HARD approach - I dunno. Chris? regards, Göran

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Magma used in production apps?
by itsme213 29 Feb '08

29 Feb '08

Are there apps in production (not necessarily mega-high volume) that use Magma? Is there a list of these someplace? Thanks - Sophie

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Maintained N to 1 index
by Sebastian Sastre 21 Feb '08

21 Feb '08

Hi there, I'm using this MaDatesAndTimesIndex which is a kind of MaKeywordIndex but to store N dates per element. When I set a halt in the message the index send to elements I saw it halting when an element is added. If I change values, with impact on the values of the index, in a previously stored element, I'm not seeing it halting. Magma is not automatically maintaining that kind of index? What one should do to achieve that? thanks, Sebastian Sastre

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MagmaCollection problem
by Oleg Korsak 17 Feb '08

17 Feb '08

Hello! I have an empty magma database (I'm using Keithy's ToDo tutorial application with Magma seasideHelper). This one: http://wiki.squeak.org/squeak/6021 So please get the latest version (7) so you can answer on my question :) In the StMagmaDatabase->#createDefaultUser (which is temporary called from #findUserByEmail) I'm initializing a database and adding one user with ' todo(a)todo.tut' email: | user | self initialize. user := StUser new. user id: 1. user email: 'todo(a)todo.tut'. user userName: 'todo'. user password: 'todo'. self addUser: user. then I'm trying to find user by email ('todo(a)todo.tz'). BUT... I'm getting a wrong result user := self users where: [:each | each read: #email at: 'todo.tz'. ]. user first explore. user first returns the first user in MagmaCollection with the WRONG email ('todo(a)todo.tz'). So how can I get nil in this case? (because there is no user with such email in database). Thanks.

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Magma use with low bandwidth and weird situation
by Hilaire Fernandes 14 Feb '08

14 Feb '08

In iStoa, the client (kids with Morphic application) connect to a Magma database through an ADSL connection. When a kids has finished with an exercice, several instances relative to kid achievements are recorded in the remote Magma database. Later the teacher can review (and replay) the kid actions and results. 1. My first constraint is the 128 kbits/s up limit used to upload in the database the instances. Indeed the client is blocked for 1 miniute waiting for the data persistence. A first idea is to compress all the serialised data sent to the Magma server. Is it possible? Other option is to embed the Magma commit in a separate thread. I did some tests, but it randomly leads to crash on the server. Is it something some of you look at? 2. Next the teacher reviews the kids activities through a web application (seaside based) + Squeak web plugin. The Squeak web plugin is used to connect to the Magma database and to replay cinematically the kids activities. From there, at each use of the plugin, a connection to the Magma database is opened, and it is slow, too slow. Any thought about how to optimise that? Best Hilaire

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#read: for magma reader
by Sebastian Sastre 13 Feb '08

13 Feb '08

Hi there, I have a kind of object stored on magmacollections which has been indexed by an attribute which returns N dates. I've made an index which is pretty much like MaKeywordIndex but for DateAndTimes. It works well. Now I need a metric on those objects to score them regarding to the number of ocurrences of the dates they will be found on the odb. So I have: scoringLevel "Answers the quantity of dates of some relevance for the receiver." ^ ((self elements where:[:reader| (reader read: #relevantDates from: (Date today subtractDays: self daysBack) asDateAndTime to: DateAndTime now)]) distinct: true) size by now I've set 2 years by answering 360*2 in daysBack but what if I want the socing for whole thing? I've tried #read: without parameters other than the index name but then I've realized is not implemented in magma reader. I wish I can do something to count occurrences of my query like: scoringLevel "Answers the quantity of dates of some relevance for the receiver." ^ ((self elements where:[:reader| reader read: #relevantDates]) distinct: true) size So taking a look in the reader and indexes I figured I put in my *MagmaExtensions this method: MagmaCollectionReader>>read: attributeSymbol "Answers a MaLargeCollectionReader with access to all its elements. NOTE: warning, is the whole thing, use smartly" ^ [:index| self readIndex: index fromHash: index lowestPossibleKey toHash: index highestPossibleKey] value: (self indexNamed: attributeSymbol) But this it's returning a MaClause and no a reader as expected? Any clue on whats happening? thanks, Sebastian Sastre

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Magma on 3.10
by Esteban Lorenzano 12 Feb '08

12 Feb '08

Hi, I just installed magma on a squeak-dev image (from Damien Cassou) based on build 7159 (latest 3.10 image) I load packages "magma client 1.0 (r40)", "magma server 1.0 (r40)" and "magma tester 1.0 (r40)" from universes and executed first "getting started" code, with a very simple modification: MagmaRepositoryController create: (FileDirectory default directoryNamed: 'repository') fullName root: Dictionary new executing this code throws a doesNotUnderstood: #open on ByteString. The message call comes from MaFileStreamPool>>renewAccess: Same code executed on a 3.9 image (from Damien Cassou, too) works fine. Is there a possible solution for this? i really need to run magma on 3.10 images. Thanks, Esteban

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Future of Morph
by Hilaire Fernandes 12 Feb '08

12 Feb '08

Regarding the recent posts on Morph. I just want to write I am very interested by what Juan is doing with Morph 3, and also about Alain Plantec work to improve Morph. I am interested because when it wil get bigger and embraced with the community, I will use it for DrGeoII project and for the bigger one iStoa.net. Both projects depend a lot on Morph and I am not always confident about its maintainability. I hope you can unit your effort for future Morph system. You already have one client ;-) Hilaire

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Repetive problem with indexed attribute
by Hilaire Fernandes 08 Feb '08

08 Feb '08

In my quest to write tests to control Magma behaviour, I have found the following problem: With a magma collection of users object defined as follow: | users | users := MagmaCollection new. users addIndex: (MaIntegerIndex attribute: #id); addIndex: (MaKeywordIndex attribute: #functions); addIndex: (MaSearchStringIndex attribute: #schoolYear). ^ users I have problem with the #functions key. functions is instanciated as an empty OrderedCollection. I can update function with #function: message functions: aCollection (self class functions includesAllOf: aCollection) ifTrue: [IFIDbSession commit: [IFIDbSession noteOldKeyFor: self. functions := aCollection]] In my test, I can do: adult functions: #(#teacher). self should: adult functions = #(#teacher). but the next one got the error (see SqueakLog enclosed) adult functions: #(#teacher #admin). self should: adult functions = #(#teacher #admin). If I change the previous test code to: adult functions: #(#director #admin ). self should: adult functions = #(#director #admin ). It is fine. It seems the problem appear when two successive changes to functions has common value, here #teacher was in both #(#teacher) and #(#teacher #admin) Please help!

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Magma February 2008