Thread: XPath and XML support
I'm doing a performance and scalability test project for a PostgreSQL user who is working with geospatial data. The data is in GML form. For instance: <watch version="9" id="flight" time="2006-08-16T10:16:36.125-07:00"> <point latitude="7" longitude="55"/> <detail> <gml:Point xmlns:gml="http://www.opengis.net/gml"> <gml:coordinates>7.0,9.0</gml:coordinates> </gml:Point> </detail> </watch> I installed PostGIS and it supports Point and coordinates very well. I an not sure what I should do with the XML content using PostgreSQL? For example, 1) Tom Dyson at http://www.throwingbeans.org/ postgresql_and_xml_updated.html says "PostgreSQL 8 ships with xpath_table to evaluate a set of XPath queries and returns the results as a virtual table." These look like good XPath functions. Are they actually in PSQL 8.1.4? I did not find them in the Windows installed version. If not, are they recommended? 2) What is the relationship of the XPath functions to the PostGIS functions? For example, will I be able to use an index to a PostGIS field? 3) If the XPath operators are not allowed, should I shred the GML into two tables (point and detail)? Any help is much appreciated. Thanks. -Frank --- Frank Cohen, Raining Data, http://www.RainingData.com, phone: 408 236 7604 http://www.xquerynow.com for free XML, XQuery and native XML database tips, techniques and solutions.
On Wed, 2006-08-23 at 16:04 -0700, Frank Cohen wrote: > I'm doing a performance and scalability test project for a PostgreSQL > user who is working with geospatial data. The data is in GML form. > For instance: > > > <watch version="9" id="flight" time="2006-08-16T10:16:36.125-07:00"> > <point latitude="7" longitude="55"/> > <detail> > <gml:Point xmlns:gml="http://www.opengis.net/gml"> > <gml:coordinates>7.0,9.0</gml:coordinates> > </gml:Point> > </detail> > </watch> > > > I installed PostGIS and it supports Point and coordinates very well. > > I an not sure what I should do with the XML content using PostgreSQL? > For example, > > 1) Tom Dyson at http://www.throwingbeans.org/ > postgresql_and_xml_updated.html says "PostgreSQL 8 ships with > xpath_table to evaluate a set of XPath queries and returns the > results as a virtual table." > > These look like good XPath functions. Are they actually in PSQL > 8.1.4? I did not find them in the Windows installed version. If not, > are they recommended? Look at contrib/xml2. The function xpath_table is in that module. I'm not familiar enough with windows to tell you how to install it, but hopefully this gives you a good starting point. Regards, Jeff Davis
On 8/24/06, Jeff Davis <pgsql@j-davis.com> wrote: > On Wed, 2006-08-23 at 16:04 -0700, Frank Cohen wrote: > > > > These look like good XPath functions. Are they actually in PSQL > > 8.1.4? I did not find them in the Windows installed version. If not, > > are they recommended? > > Look at contrib/xml2. The function xpath_table is in that module. I'm > not familiar enough with windows to tell you how to install it, but > hopefully this gives you a good starting point. > AFAIK, contrib/xml2 hasn't been ported to Windows yet (at least, this is in the current TODO list). -- Best regards, Nikolay
Thanks Nikolay: Seeing as xml2 hasn't been ported to Windows yet makes me wonder if this is going to be the best way to use XML in PostgreSQL in the long-term? Is there anything else on the boards? - Frank On Aug 24, 2006, at 4:17 AM, Nikolay Samokhvalov wrote: > On 8/24/06, Jeff Davis <pgsql@j-davis.com> wrote: >> On Wed, 2006-08-23 at 16:04 -0700, Frank Cohen wrote: >> > >> > These look like good XPath functions. Are they actually in PSQL >> > 8.1.4? I did not find them in the Windows installed version. If >> not, >> > are they recommended? >> >> Look at contrib/xml2. The function xpath_table is in that module. I'm >> not familiar enough with windows to tell you how to install it, but >> hopefully this gives you a good starting point. >> > > AFAIK, contrib/xml2 hasn't been ported to Windows yet (at least, this > is in the current TODO list). > > -- > > Best regards, > Nikolay >
On Thu, 24 Aug 2006 13:56:12 -0700, Frank Cohen wrote: > Thanks Nikolay: Seeing as xml2 hasn't been ported to Windows yet > makes me wonder if this is going to be the best way to use XML in > PostgreSQL in the long-term? Is there anything else on the boards? - > Frank > There's a lot of scope to do better than the current support, certainly. However, the "not ported to Windows" is slightly misleading - the code (like a lot of contrib code) compiles fine under Windows. Because of the dependency on libxml2, it might not often be distributed as a binary, but people are definitely using on Win32 (I'm not really a Win32 user but I have tried it and it did work). John
> -----Original Message----- > From: pgsql-general-owner@postgresql.org > [mailto:pgsql-general-owner@postgresql.org] On Behalf Of John Gray > Sent: 29 August 2006 22:49 > To: pgsql-general@postgresql.org > Subject: Re: [GENERAL] XPath and XML support > > On Thu, 24 Aug 2006 13:56:12 -0700, Frank Cohen wrote: > > > Thanks Nikolay: Seeing as xml2 hasn't been ported to Windows yet > > makes me wonder if this is going to be the best way to use XML in > > PostgreSQL in the long-term? Is there anything else on the > boards? - > > Frank > > > > There's a lot of scope to do better than the current support, > certainly. > > However, the "not ported to Windows" is slightly misleading - the code > (like a lot of contrib code) compiles fine under Windows. > Because of the > dependency on libxml2, it might not often be distributed as a > binary, but > people are definitely using on Win32 (I'm not really a Win32 > user but I > have tried it and it did work). It was only ported relatively recently (I know, I did it). It will ship with the Windows PostgreSQL 8.2 binary installer. Regards, Dave.