Short summary:
I want something like xpath_list() that returns an array
(instead of a delimited, concatenated string) when multiple
nodes exist in an XML file. It feels to me like that'd
be a better (cleaner) API.
Before I write one, does anyone already have such a
patch? If not, would people be interested if I added
xpath_array() that behaves like xpath_list() but returns
an array instead of one big string?
Or... is xpsql on gborg or some other postgresql-xml
project a better place for me to be looking?
Longer:
From the (very cool) xml2 package's README, I see
xpath_list(document,query,separator) RETURNS text
This function returns multiple values separated by the specified
separator, e.g. Value 1,Value 2,Value 3 if separator=','.
xpath_list(document,query) RETURNS text
This is a wrapper for the above function that
uses ',' as the separator.
And indeed, that's exactly what it returns:
fl=# create temporary table x (xml text);
flee=# insert into x values
('<a><b id="1">1</b><b id="2">2</b></a>');
flee=# select xpath_list(xml,'/a/b') from x;
xpath_list
------------
1,2
(1 row)
However to make use of each value, I'd then need to re-parse
that text string to make use of each of the values.
I realize I can get the effect I want using an uncommon
string as a delimiter and the string_to_array() function...
fl=# select
string_to_array(xpath_list(xml,'/a/b','##delim##')
,'##delim##') from x;
string_to_array
-----------------
{1,2}
(1 row)
... but that feels pretty ugly considering to guess what
delimiter won't be in the string.
While I'm at it, a version of xpath_nodeset:
fl=# select xpath_nodeset(xml,'/a/b') from x;
xpath_nodeset
--------------------------------
<b id="1">1</b><b id="2">2</b>
(1 row)
that returned an array of matching XML fragments
instead of all the fragments concatenated together
might also be useful.
Thoughts? Suggestions?
Ron
