mirror of https://github.com/postgres/postgres
79 lines
2.2 KiB
Plaintext
79 lines
2.2 KiB
Plaintext
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This package contains a couple of simple routines for hooking the
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expat XML parser up to PostgreSQL. This is a work-in-progress and all
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very basic at the moment (see the file TODO for some outline of what
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remains to be done).
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At present, two functions are defined, one which checks
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well-formedness, and the other which performs very simple XPath-type
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queries.
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Prerequisite:
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expat parser 1.95.0 or newer (http://expat.sourceforge.net)
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I used a shared library version -I'm sure you could use a static
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library if you wished though. I had no problems compiling from source.
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Function documentation and usage:
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---------------------------------
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pgxml_parse(text) returns bool
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parses the provided text and returns true or false if it is
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well-formed or not. It returns NULL if the parser couldn't be
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created for any reason.
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pgxml_xpath(text doc, text xpath, int n) returns text
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parses doc and returns the cdata of the nth occurence of
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the "XPath" listed. See below for details on the syntax.
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Example:
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Given a table docstore:
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Attribute | Type | Modifier
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-----------+---------+----------
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docid | integer |
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document | text |
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containing documents such as (these are archaeological site
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descriptions, in case anyone is wondering):
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<?XML version="1.0"?>
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<site provider="Foundations" sitecode="ak97" version="1">
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<name>Church Farm, Ashton Keynes</name>
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<invtype>watching brief</invtype>
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<location scheme="osgb">SU04209424</location>
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</site>
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one can type:
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select docid,
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pgxml_xpath(document,'/site/name',1) as sitename,
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pgxml_xpath(document,'/site/location',1) as location
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from docstore;
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and get as output:
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docid | sitename | location
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-------+-----------------------------+------------
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1 | Church Farm, Ashton Keynes | SU04209424
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2 | Glebe Farm, Long Itchington | SP41506500
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(2 rows)
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"XPath" syntax supported
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------------------------
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At present it only supports paths of the form:
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'tag1/tag2' or '/tag1/tag2'
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The first case will find any <tag2> within a <tag1>, the second will
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find any <tag2> within a <tag1> at the top level of the document.
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The real XPath is much more complex (see TODO file).
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John Gray <jgray@azuli.co.uk> 26 July 2001
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