Re: How to get the Object-ID from a DB-Object?
Alexander Burger writes: Hi Alex, >> i.e. can I first assign e.g. 37 to it during the object creation, and >> then let the 'id' function re-assign e.g. 9 to it when post-processing >> the newly created objects? > > Yes, sure. The object doesn't care about the meaning of that number. > > But (as also Henrik pointed out), this looks very much like a +Link or > +Joint relation, doesn't it? Storing the id of some other object sounds > like a lot of maintenance work, to keep it everything consistent. No, these numbers are already there and tell me what to link/join, so I need them for object creation. But once the linked/joined object network exists, can replace them with something more meaningfull like a unique elem-ID. -- cheers, Thorsten -- UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
Re: How to get the Object-ID from a DB-Object?
Hi Thorsten, > , > | (rel elem-id (+Number)) > ` > > and it is "reused": > > 1. first, it holds an (arbitrary) number that is used during object >creation to associate it with other objects that are created too in >the same commit. > > 2. once the db-objects are, these id's can be (and are) overwritten to >omething more meaningfull, I had my own function for this, but now I >want to use Henriks proposal (integers produced with the id function). > > Is step (1) still possible when the relation is defined as > > , > | (rel elem-id (+Key +Number)) > ` > > i.e. can I first assign e.g. 37 to it during the object creation, and > then let the 'id' function re-assign e.g. 9 to it when post-processing > the newly created objects? Yes, sure. The object doesn't care about the meaning of that number. But (as also Henrik pointed out), this looks very much like a +Link or +Joint relation, doesn't it? Storing the id of some other object sounds like a lot of maintenance work, to keep it everything consistent. ♪♫ Alex -- UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
Re: How to get the Object-ID from a DB-Object?
One more doubt: Without going into the details, assume there is a relation like this , | (rel elem-id (+Number)) ` and it is "reused": 1. first, it holds an (arbitrary) number that is used during object creation to associate it with other objects that are created too in the same commit. 2. once the db-objects are, these id's can be (and are) overwritten to omething more meaningfull, I had my own function for this, but now I want to use Henriks proposal (integers produced with the id function). Is step (1) still possible when the relation is defined as , | (rel elem-id (+Key +Number)) ` i.e. can I first assign e.g. 37 to it during the object creation, and then let the 'id' function re-assign e.g. 9 to it when post-processing the newly created objects? -- cheers, Thorsten -- UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
Re: How to get the Object-ID from a DB-Object?
Alexander Burger writes:
Hi Alex,
>> I want to export the objects to a textual representation that might be
>> edited and then committed again, so I must be able to find out which DB
>> object is associated to the textual representation.
>
> Note that in general it is not recommended to access external objects by
> their name.
>
> It is true that you can easily write it to a file, simply with 'print',
>
>(print '{33})
>
> and you can also 'read' it back again.
>
> The problem is that {33} might meanwhile be deleted from the DB, i.e.
> the block at offset 33 is returned to the free list, and reading and
> accessing this object would result in a runtime error. Or, even worse,
> this block may be re-used by some completely different object.
>
> Therefore, as Henrik pointed out, portable access to database objects is
> only meaningful via their index keys.
Yes, I think what Henrik uses is a good and simple solution.
> Concerning you intention to export objects to an editable
> representation:
>
> There is a 'dump' function exactly for that purpose. It writes arbitrary
> Pilog selections to the current output channel.
>
> Taking the salutations from demo 'app' as an example
>
> : (load "@lib/too.l")
>
> : (dump (db nm +Sal @@))
>...
>(obj ((+Sal) nm "Herr")
> sex T
> hi "Sehr geehrter Herr @1," )
>(obj ((+Sal) nm "Herr Dr.")
> sex T
> hi "Sehr geehrter Herr Dr. @1," )
>(obj ((+Sal) nm "Mr.")
> sex T
> hi "Dear Mr. @1," )
>(obj ((+Sal) nm "Mrs.")
> sex 0
> hi "Dear Mrs. @1," )
>...
>
> As you see, this is a format which can directly be 'load'ed.
Another very useful function in PicoLisp! Although in my case I need a
special syntax for the textual representation, and I think its easier to
build that syntax by getting the info from the DB objects than to parse
and modify the dumped DB.
> A typical export function for a database looks like
>
>(de dumpMyDB ()
>
>(de loadMyDB ()
>
> 'dump' also takes care of related data blobs. In the above example, all
> (the 'load'able file and the blobs) are all packed into a single TGZ
> file.
nice
>> That sounds like a solution I should copy. Just out of curiosity: in a
>> distributed database, the object ids ({3}, {1-2} ...) are not unique but
>> might be repeated on different machines?
>
> Right. The combination "file" and "offset", which specifies a given
> object, may appear on remote machines again. But there is no problem as
> long as you use indexes to access the objects.
Ok, thanks
--
cheers,
Thorsten
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Re: How to get the Object-ID from a DB-Object?
On Mon, Jan 27, 2014 at 09:55:28AM +0100, Alexander Burger wrote: > 'dump' also takes care of related data blobs. In the above example, all > (the 'load'able file and the blobs) are all packed into a single TGZ > file. Oops, slight error! Just for the records: The TGZ file holds only the blobs, the *.l file is separate. -- UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
Re: How to get the Object-ID from a DB-Object?
Hi Thorsten,
> I want to export the objects to a textual representation that might be
> edited and then committed again, so I must be able to find out which DB
> object is associated to the textual representation.
Note that in general it is not recommended to access external objects by
their name.
It is true that you can easily write it to a file, simply with 'print',
(print '{33})
and you can also 'read' it back again.
The problem is that {33} might meanwhile be deleted from the DB, i.e.
the block at offset 33 is returned to the free list, and reading and
accessing this object would result in a runtime error. Or, even worse,
this block may be re-used by some completely different object.
Therefore, as Henrik pointed out, portable access to database objects is
only meaningful via their index keys.
Concerning you intention to export objects to an editable
representation:
There is a 'dump' function exactly for that purpose. It writes arbitrary
Pilog selections to the current output channel.
Taking the salutations from demo 'app' as an example
: (load "@lib/too.l")
: (dump (db nm +Sal @@))
...
(obj ((+Sal) nm "Herr")
sex T
hi "Sehr geehrter Herr @1," )
(obj ((+Sal) nm "Herr Dr.")
sex T
hi "Sehr geehrter Herr Dr. @1," )
(obj ((+Sal) nm "Mr.")
sex T
hi "Dear Mr. @1," )
(obj ((+Sal) nm "Mrs.")
sex 0
hi "Dear Mrs. @1," )
...
As you see, this is a format which can directly be 'load'ed.
A typical export function for a database looks like
(de dumpMyDB ()
(out "myDB.l"
(prinl "# " (stamp))
(prinl)
(prinl "# Roles")
(dump (db nm +Role @@))
(println '(commit))
(prinl)
(prinl "# User")
(dump (db nm +User @@))
(println '(commit))
(prinl)
(prinl "# Shops")
(dump (db id +Shop @@))
(println '(commit))
... )
(when (dir (tmp))
(out "myDB.tgz"
(chdir (tmp)
(in (append '("tar" "cfz" "-") @)
(echo) ) ) ) ) )
(de loadMyDB ()
(when (and (info "myDB.tgz") (n0 (car @)))
(in "myDB.tgz"
(chdir (tmp)
(out '("tar" "xfz" "-")
(echo) ) ) ) )
(load "myDB.l") )
'dump' also takes care of related data blobs. In the above example, all
(the 'load'able file and the blobs) are all packed into a single TGZ
file.
> That sounds like a solution I should copy. Just out of curiosity: in a
> distributed database, the object ids ({3}, {1-2} ...) are not unique but
> might be repeated on different machines?
Right. The combination "file" and "offset", which specifies a given
object, may appear on remote machines again. But there is no problem as
long as you use indexes to access the objects.
♪♪♫ Alex
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Re: How to get the Object-ID from a DB-Object?
>
> That sounds like a solution I should copy. Just out of curiosity: in a
> distributed database, the object ids ({3}, {1-2} ...) are not unique but
> might be repeated on different machines?
>
AFAIK yes. In any case the {x...} locations are changed by the remote
functionality to avoid clashes with local objects, ie a remote object won't
have the same {x...} as it has locally on the remote machine.
This fact could be used in the creation of functions that handle remote
objects more or less transparently, a typical example would the the get
algo, let's say I do (;; Trans user) and Trans is a remote object then the
;; function infers that fact and fetches the user from the remote machine
through the local +Link pointer on that machine.
On Mon, Jan 27, 2014 at 3:16 PM, Thorsten Jolitz wrote:
> Henrik Sarvell
> writes:
>
> Hi Henrik,
>
> > why do you want to do this explicitly since it's done for
> > you implicitly in all the various type of reference relations you have
> > (typically +Link)?
>
> I want to export the objects to a textual representation that might be
> edited and then committed again, so I must be able to find out which DB
> object is associated to the textual representation.
>
> > In Macropis I simply use the convention of having a relation called id
> > auto increment (by way of http://software-lab.de/doc/refG.html#genKey )
> > , that way it doesn't matter which machine something is on, I will
> > never have to worry since something like the action /+Page/update/3/
> > always updates the object of class +Page with id 3 no matter what the
> > {x...} location might look like.
>
> That sounds like a solution I should copy. Just out of curiosity: in a
> distributed database, the object ids ({3}, {1-2} ...) are not unique but
> might be repeated on different machines?
>
> > However the impetus for this convention was actually the fact that
> > functions like db and collect need for instance a +Ref or +Key to be
> > able to fetch an object at all, having a +Key called id in all objects
> > make things so much easier.
>
> I figured that out too (-> db and collect need a +Ref or +Key) and it
> makes using a +Key id even more reasonable, I wasn't aware of the id
> functions in picolisp, so I thought about my own solution.
>
> > But anyway, to really answer your question you might want to look
> > into: http://software-lab.de/doc/refI.html#id
> >
> > And as far as the remote stuff goes with the db id and obj id combo
> > AFAIK you have to implement it yourself, you might want to start by
> > reading this discussion:
> > http://comments.gmane.org/gmane.lisp.picolisp.general/2849
>
> Thanks for the tips, very helpful!
>
>
> > On Sun, Jan 26, 2014 at 6:56 PM, Thorsten Jolitz
> > wrote:
> >
> > Thorsten Jolitz
> > writes:
> >
> > ,--
> > ---
> > | Sorry, I sent this post accidentally before I was finished, so I
> > have to
> > | send it again.
> > `--
> > ---
> >
> >
> >
> > Hi List,
> >
> > say I want to use the internal Object ID of database object as a
> > unique string
> > identifier (useful e.g. for export in a textformat), i.e.
> > something
> > like:
> >
> >
> > ,-
> >
> > | : (put '{33} 'ID "{33}")
> >
> > `-
> >
> > how do I get the ID from a database object in a program? And is
> > there
> > some unique identifier for a database too, so that object-id and
> > db-id
> > could be combined into a globally unique id?
> >
> >
> >
> >
> > --
> > cheers,
> > Thorsten
> >
> > --
> > UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
> >
> >
> >
>
> --
> cheers,
> Thorsten
>
> --
> UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
>
Re: How to get the Object-ID from a DB-Object?
Henrik Sarvell
writes:
Hi Henrik,
> why do you want to do this explicitly since it's done for
> you implicitly in all the various type of reference relations you have
> (typically +Link)?
I want to export the objects to a textual representation that might be
edited and then committed again, so I must be able to find out which DB
object is associated to the textual representation.
> In Macropis I simply use the convention of having a relation called id
> auto increment (by way of http://software-lab.de/doc/refG.html#genKey )
> , that way it doesn't matter which machine something is on, I will
> never have to worry since something like the action /+Page/update/3/
> always updates the object of class +Page with id 3 no matter what the
> {x...} location might look like.
That sounds like a solution I should copy. Just out of curiosity: in a
distributed database, the object ids ({3}, {1-2} ...) are not unique but
might be repeated on different machines?
> However the impetus for this convention was actually the fact that
> functions like db and collect need for instance a +Ref or +Key to be
> able to fetch an object at all, having a +Key called id in all objects
> make things so much easier.
I figured that out too (-> db and collect need a +Ref or +Key) and it
makes using a +Key id even more reasonable, I wasn't aware of the id
functions in picolisp, so I thought about my own solution.
> But anyway, to really answer your question you might want to look
> into: http://software-lab.de/doc/refI.html#id
>
> And as far as the remote stuff goes with the db id and obj id combo
> AFAIK you have to implement it yourself, you might want to start by
> reading this discussion:
> http://comments.gmane.org/gmane.lisp.picolisp.general/2849
Thanks for the tips, very helpful!
> On Sun, Jan 26, 2014 at 6:56 PM, Thorsten Jolitz
> wrote:
>
> Thorsten Jolitz
> writes:
>
> ,--
> ---
> | Sorry, I sent this post accidentally before I was finished, so I
> have to
> | send it again.
> `--
> ---
>
>
>
> Hi List,
>
> say I want to use the internal Object ID of database object as a
> unique string
> identifier (useful e.g. for export in a textformat), i.e.
> something
> like:
>
>
> ,-
>
> | : (put '{33} 'ID "{33}")
>
> `-
>
> how do I get the ID from a database object in a program? And is
> there
> some unique identifier for a database too, so that object-id and
> db-id
> could be combined into a globally unique id?
>
>
>
>
> --
> cheers,
> Thorsten
>
> --
> UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
>
>
>
--
cheers,
Thorsten
--
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Re: How to get the Object-ID from a DB-Object?
Hi Thorsten, why do you want to do this explicitly since it's done for you
implicitly in all the various type of reference relations you have
(typically +Link)?
In Macropis I simply use the convention of having a relation called id auto
increment (by way of http://software-lab.de/doc/refG.html#genKey ) , that
way it doesn't matter which machine something is on, I will never have to
worry since something like the action /+Page/update/3/ always updates the
object of class +Page with id 3 no matter what the {x...} location might
look like.
However the impetus for this convention was actually the fact that
functions like db and collect need for instance a +Ref or +Key to be able
to fetch an object at all, having a +Key called id in all objects make
things so much easier.
But anyway, to really answer your question you might want to look into:
http://software-lab.de/doc/refI.html#id
And as far as the remote stuff goes with the db id and obj id combo AFAIK
you have to implement it yourself, you might want to start by reading this
discussion: http://comments.gmane.org/gmane.lisp.picolisp.general/2849
On Sun, Jan 26, 2014 at 6:56 PM, Thorsten Jolitz wrote:
> Thorsten Jolitz
> writes:
>
> ,-
> | Sorry, I sent this post accidentally before I was finished, so I have to
> | send it again.
> `-
>
>
> Hi List,
>
> say I want to use the internal Object ID of database object as a unique
> string
> identifier (useful e.g. for export in a textformat), i.e. something
> like:
>
> ,-
> | : (put '{33} 'ID "{33}")
> `-
>
> how do I get the ID from a database object in a program? And is there
> some unique identifier for a database too, so that object-id and db-id
> could be combined into a globally unique id?
>
>
> --
> cheers,
> Thorsten
>
> --
> UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
>
Re: How to get the Object-ID from a DB-Object?
Thorsten Jolitz
writes:
,-
| Sorry, I sent this post accidentally before I was finished, so I have to
| send it again.
`-
Hi List,
say I want to use the internal Object ID of database object as a unique string
identifier (useful e.g. for export in a textformat), i.e. something
like:
,-
| : (put '{33} 'ID "{33}")
`-
how do I get the ID from a database object in a program? And is there
some unique identifier for a database too, so that object-id and db-id
could be combined into a globally unique id?
--
cheers,
Thorsten
--
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