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Re: xpath not a good replacement for xpath_string

From: Andrew Dunstan <andrew(at)dunslane(dot)net>
To: pgsql(at)mohawksoft(dot)com
Cc: PostgreSQL <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: xpath not a good replacement for xpath_string
Date: 2009-07-28 20:00:55
Message-ID: 4A6F58F7.3000007@dunslane.net (view raw or flat)
Thread:
Lists: pgsql-hackers

pgsql(at)mohawksoft(dot)com wrote:
> Sorry to bring this up, I know you've been fighting about XML for a while.
>
> Currently, I am using XML2 functionality and have tried to get the newer
> XPath function to work similarly, but can't quite seem to do it.
>
> I think the current xpath function is too limited. (The docs said to post
> problems to hackers if I have an issue.)
>
> For instance, we have a web application that uses java with an XML class
> serializer/deserializer Xstream. It creates XML that looks like this:
>
> <com.company.local.myclass>
>     <uuid>b5212259-a91f-4dca-a547-4fe89cf2f32c</uuid>
>     <email>joe(at)somedomain(dot)com</email>
> </com.company.local.myclass>
>
> My current strategy is to use xml2 as:
>
> select xpath_string(datum, E'/com\.company\.local\.myclass/uuid) as uuid
> from table;
>
> Which produces a usable:
> b5212259-a91f-4dca-a547-4fe89cf2f32c
>
> I have been trying to use xpath
> select xpath(E'/com\.company\.local\.myclass/uuid', XMLPARSE(CONTENT
> datum)) as uuid from table;
>
> Which produces an unusable:
> {<uuid>b5212259-a91f-4dca-a547-4fe89cf2f32c</uuid>}
>
>
>
>   

This is really a usage question, which doesn't belong on -hackers. 
However, here is how to do what you want:

andrew=# select 
(xpath($$/com.company.local.myclass/uuid/text()$$,$$<com.company.local.myclass>
    <uuid>b5212259-a91f-4dca-a547-4fe89cf2f32c</uuid>
    <email>joe(at)somedomain(dot)com</email>
</com.company.local.myclass>
$$::xml))[1]::text as uuid;
                 uuid                
--------------------------------------
 b5212259-a91f-4dca-a547-4fe89cf2f32c
(1 row)


cheers

andrew


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Next:From: Kevin GrittnerDate: 2009-07-28 20:06:48
Subject: Re: xpath not a good replacement for xpath_string
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