Re: [AgileWiki] Query never ends

[Bill la F. <laf...@ya...>]

Sougata,

Never fear, it is always good to hear from you. And of
late, the discussion list(s) have been a bit too
quiet, so it is especially good to hear from you. I'll
look at your code tonight or tomorrow morning, with
pleasure!

As for your question, my answer is that this is not a
RDBMS, but rather it is an OODBMS. So there is no
record. There are objects with various kinds of
attributes. Though to be fair, in TKS I refer to
record ids, but they are more correctly named in ArkDb
as rolon ids.

Now when you do the add entry command, the current
context will be the rolon to be updated. You are
assured this because in the init method of the
command, you attach the command to the
SiimpleLedgerRolon class. (The init method is called
when the program starts--commands are singletons.)

You can then get the Rolon class (the data proxy) like
this: 
SimpleLedgerRolon
slr=(SimpleLedgerRolon)session.getContext();

Now because slr inherits from TableRolon, you can use
the accessor methods on TableRolon to manipulate the
document property. The value of the document property
is a text document in comma separated form.

To update it (in evaluateForm), you just call:
slr.setDoc(newvalue);

You can also access the content this way:
List<List<String>>
content=slr.getContent(Timestamp.NOW);

(Note that ALL queries require a timestamp, while
updates ASSUME a time of Timestamp.NOW, which is
current time.)

You may also consider using the columnIndex and
getCellInRowNoBraces methods defined in TableRolon.

Note that the first list in the list of lists returned
by getContent is the list of column names.

And when you call setContent(newvalue), the first line
must be the column names separated by commas.

Now as for a bit of what's going on..

You will see that getContent access class
org.agilewiki.ark.TableContent. This is a cache
object. It makes queries fast, but creates a problem
when you make changes. This is handled in
TableRolon.setDoc by the call to invalidateContent,
which purges the old content from the cache.

Another thing you will see are references to decRef.
This has to do with reference counting used to manage
cache objects. When you access a cache object, its
reference count is automaticly incrimented, so
getContent does a decref right after making a copy of
the data it wants.

I hope this is helpful. No doubt it will lead to more
questions, but you know my prefered approach--code a
little, learn a little. I also like frequent code
reviews--it is important to nail misconceptions early.

Now, just to go a very small bit deeper, TKS maintains
simple property/value pairs, tables of key/value pairs
and inverted tables of key/value pairs. These are
largely distinguished by naming conventions.

Looking in another direction, there are only a few
caches maintained by the ark:
TableContent,
Pathname and
Topics.

Additionally, TKS maintains a cache of tables of
key/value pairs. But note please that the TKS tables
have absolutely nothing to do with Ark-level tables,
which are really just csf documents.

At an even lower level, btree keeps a cache of btree
nodes.

The important thing to remember about all caches is
that they are transactionally aware. So if you make a
change that gets recorded in a cache in the context of
a transaction which subsequently gets aborted, the
cache is automagicly cleared for you, as well as
having the database restored to its prior value.

And the thing to remember about transactions is that
they can be nested. So you can partially undo and
still continue. Its lots of fun.

Enough? :-)

Bill

--- sougata bhattacharya <sou...@ya...>
wrote:

> Hi Bill,
>   I guess I am very poor so my query never ends. But
> this is my style I never stop asking question. I
> always want to know in and out of every
> funtionality. Please don't get frastrated.
>   Here I am enclosing the Add entry form and Cmd. I
> could test it because of I guess yesterday I didn't
> check out whole code , partly I did. Anyway I will
> test it today.
>   I think the code for inserting data is not
> correct.
>   Now the question,
>   Could you  please let me know how do you retrieve
> a record(Rolon) for a given serach criteria and how
> do you save or update?
>   Cheers
>   Sougata
> 
> 
> Thanks 
> Sougata
> Cell +919342501276
> 
> 				
> ---------------------------------
>  Send free SMS to your Friends on Mobile from your
> Yahoo! Messenger Download now


Send instant messages to your online friends http://in.messenger.yahoo.com