future development of xml capabilities

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Hello Postgres Gurus,

I am doing some research regarding the postgres native xml type, I found th=
at the xml type can not be indexed, I found some work arounds for it but, I=
was wondering if there were any plans to implement indexing on a xpath exp=
ression in future releases on Postges like Postgres 9?

Thank you,
Sncerely,
Kasia

------------------------------------------------------------ ---------------=
------------------------------------------------------------ --------------8=
..3 has integrated xpath function. There is gap in XML support, because XML =
type isn't supported with GIST or GIN index. So xpath function returns arra=
y of xml values. But we can write custom casting to int array:

CREATE OR REPLACE FUNCTION xml_list_to_int(xml[])
RETURNS int[] AS $$
SELECT ARRAY(SELECT to_number(($1[i])::text,'999999.99')::int
FROM generate_series(1, array_upper($1,1)) g(i))
$$ LANGUAGE SQL IMMUTABLE;

CREATE CAST (xml[] AS int[]) WITH FUNCTION xml_list_to_int(xml[]);

-- array of integers are supported with GIST
CREATE INDEX fx ON foo USING
GIN((xpath('//id/text()',order_in_xml)::int[]));
8.13.3. Accessing XML Values
The xml data type is unusual in that it does not provide any comparison ope=
rators. This is because there is no well-defined and universally useful com=
parison algorithm for XML data. One consequence of this is that you cannot =
retrieve rows by comparing an xml column against a search value. XML values=
should therefore typically be accompanied by a separate key field such as =
an ID. An alternative solution for comparing XML values is to convert them =
to character strings first, but note that character string comparison has l=
ittle to do with a useful XML comparison method.
Since there are no comparison operators for the xml data type, it is not po=
ssible to create an index directly on a column of this type. If speedy sear=
ches in XML data are desired, possible workarounds include casting the expr=
ession to a character string type and indexing that, or indexing an XPath e=
xpression. Of course, the actual query would have to be adjusted to search =
by the indexed expression.
The text-search functionality in PostgreSQL can also be used to speed up fu=
ll-document searches of XML data. The necessary preprocessing support is, h=
owever, not yet available in the PostgreSQL distribution.

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<body lang=3DEN-US link=3Dblue vlink=3Dpurple>

<div class=3DSection1>

Hello Postgres Gurus,<o:p></o:p>

<o:p> </o:p>

I am doing some research regarding the postgres native=
xml
type, I found that the xml type can not be indexed, I found some work aroun=
ds
for it but, I was wondering if there were any plans to implement indexing o=
n a
xpath expression in future releases on Postges like Postgres 9?<o:p></o:p><=
/p>

<o:p> </o:p>

Thank you, <o:p></o:p>

Sncerely,<o:p></o:p>

Kasia <o:p></o:p>

<o:p> </o:p>

------------------------------------------------------=
------------------------------------------------------------ ---------------=
--------------------8.3
has integrated xpath function. There is gap in XML support, because XML typ=
e
isn't supported with GIST or GIN index. So xpath function returns array of =
xml
values. But we can write custom casting to int array:<o:p></o:p>

<o:p> </o:p>

CREATE
OR REPLACE FUNCTION xml_list_to_int(xml[])<o:p></o:p>

RETURNS
int[] AS $$<o:p></o:p>

SELECT
ARRAY(SELECT to_number(($1[i])::text,'999999.99')::int<o:p></o:p></p=
>

 &nbs=
p;
FROM generate_series(1, array_upper($1,1)) g(i))<o:p></o:p>

$$
LANGUAGE SQL IMMUTABLE;<o:p></o:p>

<o:p> </o:p>

CREATE
CAST (xml[] AS int[]) WITH FUNCTION xml_list_to_int(xml[]);<o:p></o:p></spa=
n>

<o:p> </o:p>

-- array
of integers are supported with GIST<o:p></o:p>

CREATE
INDEX fx ON foo USING<o:p></o:p>

GIN((xpath('//id/text()',order_in_xml)::int[]));<o:p></o:p>

<a
name=3DAEN6767>8.13.3.
Accessing XML Values</a><o:p></o:p>

The </span=
>xml data type=
is
unusual in that it does not provide any comparison operators. This is becau=
se there
is no well-defined and universally useful comparison algorithm for XML data=
..
One consequence of this is that you cannot retrieve rows by comparing an </=
span>xml column ag=
ainst
a search value. XML values should therefore typically be accompanied by a
separate key field such as an ID. An alternative solution for comparing XML
values is to convert them to character strings first, but note that charact=
er
string comparison has little to do with a useful XML comparison method. <o:=
p></o:p>

Since ther=
e are
no comparison operators for the xml data type, it is not possible to create an inde=
x
directly on a column of this type. If speedy searches in XML data are desir=
ed,
possible workarounds include casting the expression to a character string t=
ype
and indexing that, or indexing an XPath expression. Of course, the actual q=
uery
would have to be adjusted to search by the indexed expression. <o:p></o:p><=
/span>

The text-s=
earch
functionality in PostgreSQL can also be used to speed up full-document sear=
ches
of XML data. The necessary preprocessing support is, however, not yet avail=
able
in the PostgreSQL distribution. <o:p></o:p>

<o:p> </o:p>

</div>

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future development of xml capabilities

Re: future development of xml capabilities