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External
Since: Nov 10, 2008
Posts: 3
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(Msg. 1) Posted: Mon Nov 10, 2008 7:17 am
Post subject: native xml processing vs what Postgres and Oracle offer
Archived from groups: comp>databases>theory (more info?)
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I'm thinking about starting a hobby project.
I wrote a files-based Bulletin Board years ago.
I'd like to convert it to a more database-like system, so
password-identified users could edit old posts.
Forums are inherently hierarchical and hierarchies are
tough with relations. I have modeled relational hierarchies in
the past, with what Joe Celko calls "path enumeration."
That works, but it's a bit ugly and making indexes on loooong
path-strings that all start off the same way is messy.
I'd rather work directly with hierarchies: with XML.
For native XML processing you can work with SleepyCat,
Exist or even Xindice (or expensive proprietary products
like Mark Logic or Ipedo).
But Oracle and Postgres have a way to stuff XML blobs
into a column now, and also a way to query with XPath
over those XML blobs
The native XML databases (SleepyCat etc) all require running a tomcat
server, while postgres is a bit easier to setup and install.
PUNCHLINE QUESTION, sort of.
I've worked with SleepyCat, Exist and Tomcat.
It's pretty powerful stuff and it has a lot to offer.
Mapping between GUI and data is oh so easy with
hierarchies, compared to relations. But what about
performance? I've never worked with Oracle/Postgres
XML XPath querying. And I've heard rumors it's dog slow
above a certain size/traffic threshold.
Any comments? Anybody done much with Postgres/XML?
Have any comparisons to SleepyCat? |
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External
Since: May 03, 2008
Posts: 8
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(Msg. 2) Posted: Mon Nov 10, 2008 11:07 am
Post subject: Re: native xml processing vs what Postgres and Oracle offer [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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On Nov 10, 11:40 am, paul c wrote:
> Suggest that it is more accurate to say that forums are typically
> implemented with hierarchical techniques. It would be even more
> accurate to say that forums are inherently ordered, eg., by date & time
> within topic.
I'm not sure what you point was.
Yes, forum "topic headings" are ordered by date and
time. But each topic also has 0 or more child responses, and child
responses might
be responses to responses, rather than responses to topic headings.
That's a tree
(a root node with nested children). And a tree is a hierarchy. You
do need all those
parent/child relationships.
Using relations to model hierarchies is possible but tricky (Joe Celko
has a good book).
With XML and XPath it is a snap. "Relational Databases" like Oracle
and Postgres and now Mysql_5.1 (it turns out)
do now (also) support XPath queries over XML (hybrid systems where the
XML is stored as big
text blob....while new system functions khow how o forget all about
SQL
and do XPath over those blobs). The how-its-done details are a
little more straightforward with
'nativel XML' databases. But conceptually (from a client developer's
point of view) it's all
much the same. Hierarchical XML is better at hierarchies than
relations. |
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External
Since: Jan 11, 2008
Posts: 44
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(Msg. 3) Posted: Mon Nov 10, 2008 12:32 pm
Post subject: Re: native xml processing vs what Postgres and Oracle offer [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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On Nov 10, 11:07 am, whileone wrote:
> Hierarchical XML is better at hierarchies than relations.
You would have a hard time convincing anybody here that XML is
particularly good at *anything*. Now, if you want to talk about
representing hierarchies in relational databases, there is a lot of
sources on the web. It is as good if no better quality than any
alternative solution that has XML buzzword attached to it. And, yes,
messy technology can't suggest anything any optimization insight, so
be prepared to all kinds of performance issues. >> Stay informed about: native xml processing vs what Postgres and Oracle offer |
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External
Since: May 03, 2008
Posts: 8
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(Msg. 4) Posted: Mon Nov 10, 2008 12:33 pm
Post subject: Re: native xml processing vs what Postgres and Oracle offer [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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On Nov 10, 1:20 pm, paul c wrote:
> Forums are *not* inherently hierarchical. You can choose to present
> them that way, but it's not necessary and possibly misleading.
>
Oy yoy yoy.
This thread started off by me (with a different reader, different
login name)
saying "I have a files-based forum that I WROTE that I want to convert
to a more database like system."
Well, MY FORUM is hierarchical. I want to preserve that.
In my forum every post is either a topic heading, a response
directly to a topic heading, or a response to a response.
The parent/child relationships are important.
I was not at any point referring to usenet.
The subject was: forums that happen to be hierarchical,
but you had to read too carefully to gather that, perhaps. >> Stay informed about: native xml processing vs what Postgres and Oracle offer |
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External
Since: May 03, 2008
Posts: 8
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(Msg. 5) Posted: Mon Nov 10, 2008 12:41 pm
Post subject: Re: native xml processing vs what Postgres and Oracle offer [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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External
Since: Aug 15, 2007
Posts: 659
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(Msg. 6) Posted: Mon Nov 10, 2008 2:25 pm
Post subject: Re: native xml processing vs what Postgres and Oracle offer [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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salmobytes wrote:
....
> Forums are inherently hierarchical and hierarchies are
> tough with relations. I have modeled relational hierarchies in
> the past, with what Joe Celko calls "path enumeration."
> That works, but it's a bit ugly and making indexes on loooong
> path-strings that all start off the same way is messy.
> ...
Suggest that it is more accurate to say that forums are typically
implemented with hierarchical techniques. It would be even more
accurate to say that forums are inherently ordered, eg., by date & time
within topic. I don't know what a relational hierarchy could be, but
for sure the RM is not concerned with ordering. I suspect you are not
talking about real hierarchies but rather about graphical presentation
techniques, about which the RM has nothing to say.
The forums I see are concerned with messages but not message content,
whereas it is the readers who are concerned with message content, eg.,
it is the audience who operate on the content, not the system. I think
you are talking about using the RM for physical storage, implying that
you don't need its inference ability and in the same breath saying that
it is ponderous to use the RM to implement ordering. Well, if that's
what you mean, yes it is ponderous to use the RM to implement ordering
because the RM doesn't support ordering in the first place! >> Stay informed about: native xml processing vs what Postgres and Oracle offer |
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External
Since: Aug 15, 2007
Posts: 659
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(Msg. 7) Posted: Mon Nov 10, 2008 4:26 pm
Post subject: Re: native xml processing vs what Postgres and Oracle offer [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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whileone wrote:
> On Nov 10, 11:40 am, paul c wrote:
>
>> Suggest that it is more accurate to say that forums are typically
>> implemented with hierarchical techniques. It would be even more
>> accurate to say that forums are inherently ordered, eg., by date & time
>> within topic.
>
> I'm not sure what you point was.
Forums are *not* inherently hierarchical. You can choose to present
them that way, but it's not necessary and possibly misleading.
>
> Yes, forum "topic headings" are ordered by date and
> time. But each topic also has 0 or more child responses, and child
> responses might
> be responses to responses, rather than responses to topic headings.
> That's a tree
> (a root node with nested children). And a tree is a hierarchy. You
> do need all those
> parent/child relationships.
>
Believe that if you want but there is no guarantee in any forum I've
ever seen that response n, quoting response n-1, has any relationship to
say, response n-2, or vice-versa. It might be seen as some kind of
graph but not necessarily a tree.
(Usenet rfc 1036 dictates a generated value called MESSAGE-ID. I gather
that many html-based forums can't guarantee such an attribute, maybe
that complicates them. RM doesn't say anything about generated
attribute values, except indirectly in the Information Principle.)
> Using relations to model hierarchies is possible but tricky (Joe Celko
> has a good book).
> With XML and XPath it is a snap. "Relational Databases" like Oracle
> and Postgres and now Mysql_5.1 (it turns out)
> do now (also) support XPath queries over XML (hybrid systems where the
> XML is stored as big
> text blob....while new system functions khow how o forget all about
> SQL
> and do XPath over those blobs). The how-its-done details are a
> little more straightforward with
> 'nativel XML' databases. But conceptually (from a client developer's
> point of view) it's all
> much the same. Hierarchical XML is better at hierarchies than
> relations.
>
>
>
Just an aside, I suspect that these relatively low-level programming
gizmos result in implementations that are just as complicated as the
rarely implemented TCLOSE relational operator. One reason I think
TCLOSE is fundamental is that while a relation such as {Part#,
Sub-Part#} is capable of the same information content as a tree, I
believe that without something akin to TCLOSE, it is impossible to
express certain constraints, such as preventing cycles. >> Stay informed about: native xml processing vs what Postgres and Oracle offer |
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External
Since: Aug 15, 2007
Posts: 659
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(Msg. 8) Posted: Mon Nov 10, 2008 4:26 pm
Post subject: Re: native xml processing vs what Postgres and Oracle offer [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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whileone wrote:
> On Nov 10, 1:20 pm, paul c wrote:
>> Forums are *not* inherently hierarchical. You can choose to present
>> them that way, but it's not necessary and possibly misleading.
>>
> Oy yoy yoy.
> This thread started off by me (with a different reader, different
> login name)
> saying "I have a files-based forum that I WROTE that I want to convert
> to a more database like system."
>
> Well, MY FORUM is hierarchical. I want to preserve that.
> In my forum every post is either a topic heading, a response
> directly to a topic heading, or a response to a response.
>
Have it your way, but that sounds like three distinct relations to me.
(That is, if the RM is to be used. Just out of curiousity, what is
wrong with two relations, posts that aren't responded to and posts that
are responses?)
> The parent/child relationships are important.
> I was not at any point referring to usenet.
> The subject was: forums that happen to be hierarchical,
> but you had to read too carefully to gather that, perhaps.
>
>
>
As we know, it is sadly true that the technocrats will usually tend
towards force-fitting an application to their pet programming protocol.
Usually, when Joe C's name is mentioned in a theory group, one may
safely stop reading. I'll admit there are exceptions, but he can
obfuscate with the best of them. >> Stay informed about: native xml processing vs what Postgres and Oracle offer |
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External
Since: Jan 15, 2008
Posts: 1017
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(Msg. 9) Posted: Mon Nov 10, 2008 5:25 pm
Post subject: Re: native xml processing vs what Postgres and Oracle offer [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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whileone wrote:
> On Nov 10, 1:20 pm, paul c wrote:
>
>>Forums are *not* inherently hierarchical. You can choose to present
>>them that way, but it's not necessary and possibly misleading.
>
> Oy yoy yoy.
> This thread started off by me (with a different reader, different
> login name)
> saying "I have a files-based forum that I WROTE that I want to convert
> to a more database like system."
>
> Well, MY FORUM is hierarchical. I want to preserve that.
Ordinarily, when one re-writes something from scratch, one tries to
correct the fundamental design flaws from the first version. If you want
to go to extra effort to perpetuate your design flaws, nobody will stop you.
What I don't understand is why you would want to publicise the fact or
talk about it in public. >> Stay informed about: native xml processing vs what Postgres and Oracle offer |
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External
Since: Oct 31, 2008
Posts: 27
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(Msg. 10) Posted: Wed Nov 19, 2008 7:41 am
Post subject: Re: native xml processing vs what Postgres and Oracle offer [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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On Nov 10, 3:33 pm, whileone wrote:
> On Nov 10, 1:20 pm, paul c wrote:> Forums are *not* inherently hierarchical. You can choose to present
> > them that way, but it's not necessary and possibly misleading.
>
> Oy yoy yoy.
> This thread started off by me (with a different reader, different
> login name)
> saying "I have a files-based forum that I WROTE that I want to convert
> to a more database like system."
>
> Well, MY FORUM is hierarchical. I want to preserve that.
> In my forum every post is either a topic heading, a response
> directly to a topic heading, or a response to a response.
>
> The parent/child relationships are important.
> I was not at any point referring to usenet.
> The subject was: forums that happen to be hierarchical,
> but you had to read too carefully to gather that, perhaps.
Actually, usenet is often displayed as being hierarchical, for
instance with so called "threaded" newsreaders, because within a list
of discussions, replies to replies are often more comprehensible when
you can follow the subthreads.
This is not just your preference, this is a very typical way of
viewing discussions, if you get any flack from that, its not because
of the nature of your design, its the fault of the relational
advocates that get blinded to these sorts of problems for which the
relational data model is not the optimal solution. As you pointed out,
even the major vendors are supporting different solutions, any flack
you'll get is simply from those dogmatic enough to pound every fixture
with a hammer, even if that particular fixture might be better
fastened with a screwdriver.
Not everyone with a relational bent is like that, but when posting
here you sort of have to put up with that particular breed of poster.
2 cents. >> Stay informed about: native xml processing vs what Postgres and Oracle offer |
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External
Since: Jan 22, 2008
Posts: 177
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(Msg. 11) Posted: Wed Nov 19, 2008 7:55 pm
Post subject: Re: native xml processing vs what Postgres and Oracle offer [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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On Nov 11, 5:20 am, paul c wrote:
> whileone wrote:
> > Yes, forum "topic headings" are ordered by date and
> > time. But each topic also has 0 or more child responses, and child
> > responses might
> > be responses to responses, rather than responses to topic headings.
> > That's a tree
> > (a root node with nested children). And a tree is a hierarchy. You
> > do need all those
> > parent/child relationships.
>
> Believe that if you want but there is no guarantee in any forum I've
> ever seen that response n, quoting response n-1, has any relationship to
> say, response n-2, or vice-versa. It might be seen as some kind of
> graph but not necessarily a tree.
If every post apart from the first post for a topic is made in
response to a previously existing post then inevitably it is possible
to define a tree structure.
Are you suggesting:
1) that isn't actually the case;
2) a post shouldn't actually be regarded as a response to some
previous post; or
3) the tree structure can be defined but isn't necessarily
pertinent? >> Stay informed about: native xml processing vs what Postgres and Oracle offer |
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External
Since: Aug 15, 2007
Posts: 659
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(Msg. 12) Posted: Wed Nov 19, 2008 10:25 pm
Post subject: Re: native xml processing vs what Postgres and Oracle offer [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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wrote:
> On Nov 10, 3:33 pm, whileone wrote:
>> On Nov 10, 1:20 pm, paul c wrote:> Forums are *not* inherently hierarchical. You can choose to present
>>> them that way, but it's not necessary and possibly misleading.
>> Oy yoy yoy.
>> This thread started off by me (with a different reader, different
>> login name)
>> saying "I have a files-based forum that I WROTE that I want to convert
>> to a more database like system."
>>
>> Well, MY FORUM is hierarchical. I want to preserve that.
>> In my forum every post is either a topic heading, a response
>> directly to a topic heading, or a response to a response.
>>
>> The parent/child relationships are important.
>> I was not at any point referring to usenet.
>> The subject was: forums that happen to be hierarchical,
>> but you had to read too carefully to gather that, perhaps.
>
> Actually, usenet is often displayed as being hierarchical, for
> instance with so called "threaded" newsreaders, because within a list
> of discussions, replies to replies are often more comprehensible when
> you can follow the subthreads.
> ...
Nobody said there's anything wrong with hierarchical displays (or
hierarchical physical storage for that matter).
> This is not just your preference, this is a very typical way of
> viewing discussions, if you get any flack from that, its not because
> of the nature of your design, its the fault of the relational
> advocates that get blinded to these sorts of problems for which the
> relational data model is not the optimal solution. As you pointed out,
> even the major vendors are supporting different solutions, any flack
> you'll get is simply from those dogmatic enough to pound every fixture
> with a hammer, even if that particular fixture might be better
> fastened with a screwdriver.
>
> Not everyone with a relational bent is like that, but when posting
> here you sort of have to put up with that particular breed of poster.
> 2 cents.
>
As the general level of literacy continues to decline more and more of
those who fail to recognize the possibility of a logical model will have
to put up with that dwindling breed. >> Stay informed about: native xml processing vs what Postgres and Oracle offer |
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External
Since: Aug 15, 2007
Posts: 659
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(Msg. 13) Posted: Thu Nov 20, 2008 9:25 am
Post subject: Re: native xml processing vs what Postgres and Oracle offer [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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David BL wrote:
> On Nov 11, 5:20 am, paul c wrote:
>> whileone wrote:
>
>>> Yes, forum "topic headings" are ordered by date and
>>> time. But each topic also has 0 or more child responses, and child
>>> responses might
>>> be responses to responses, rather than responses to topic headings.
>>> That's a tree
>>> (a root node with nested children). And a tree is a hierarchy. You
>>> do need all those
>>> parent/child relationships.
>> Believe that if you want but there is no guarantee in any forum I've
>> ever seen that response n, quoting response n-1, has any relationship to
>> say, response n-2, or vice-versa. It might be seen as some kind of
>> graph but not necessarily a tree.
>
> If every post apart from the first post for a topic is made in
> response to a previously existing post then inevitably it is possible
> to define a tree structure.
>
> Are you suggesting:
> 1) that isn't actually the case;
> 2) a post shouldn't actually be regarded as a response to some
> previous post; or
> 3) the tree structure can be defined but isn't necessarily
> pertinent?
>
3). - Traditionally, most email and news programs have rolled their own
file structure with a point of view that sprang from a pet programming
language and whatever OS file support was available, ignoring the
possibility of Codd's approach which emphasized the structure of data as
the central focus, especially his information principle and the relation
as the basic programming interface and, dare I say, his rather universal
operators. The result is that most mail servers and readers have
extremely arcane programming operators and probably don't offer the
ability to manipulate more than a few of the many tags that have been
defined in the rfc's. 1) and 2) are simply possibly aspects for end users. >> Stay informed about: native xml processing vs what Postgres and Oracle offer |
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External
Since: Aug 15, 2007
Posts: 659
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(Msg. 14) Posted: Thu Nov 20, 2008 9:25 am
Post subject: Re: native xml processing vs what Postgres and Oracle offer [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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paul c wrote:
> David BL wrote:
....
To try to say it a different way, if one is determined to organize data
in a hierarchy, there isn't much point in asking how data theory
applies. (My theory as to why this happens so often has to do with the
long-time but, I think, discredited, programming saw of starting with
the desired output and working backwards. That is more popular than
ever, from what I can see. The naive continue to seek technocratic
blessing but are usually satified by the assurances of witch doctors.) >> Stay informed about: native xml processing vs what Postgres and Oracle offer |
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External
Since: Aug 15, 2007
Posts: 659
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(Msg. 15) Posted: Thu Nov 20, 2008 10:25 am
Post subject: Re: native xml processing vs what Postgres and Oracle offer [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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David BL wrote:
....
> 3) the tree structure can be defined but isn't necessarily
> pertinent
Regarding "pertinent" some people may get a few laughs from the
Scientific American article, now about ten years old, at:
http://www.sciam.com/article.cfm?id=xml-and-the-second-genera
The first paragraph comes right out and advocates the Humpty-Dumpty
school of design:
"Give people a few hints, and they can figure out the rest. They can
look at this page, see some large type followed by blocks of small type
and know that they are looking at the start of a magazine article. They
can look at a list of groceries and see shopping instructions. They can
look at some rows of numbers and understand the state of their bank
account."
I'm not laughing at the authors, they sound like cheerful, earnest
idiots who get to their "point" without much ado, eg., before describing
their enhancement to HTML, they acknowledge that HTML is "superficial",
and they aren't going to let that slow them down! But the Sci Am
editors who let this bumpf ride could have been accomplices to the
tailor in the "Emperor's New Clothes". I would have thought a serious
proposal would discuss http, not html. >> Stay informed about: native xml processing vs what Postgres and Oracle offer |
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