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| -rw-r--r-- | doc/src/sgml/datatype.sgml | 150 |
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diff --git a/doc/src/sgml/datatype.sgml b/doc/src/sgml/datatype.sgml index 68ff7afd039..c589c2c3455 100644 --- a/doc/src/sgml/datatype.sgml +++ b/doc/src/sgml/datatype.sgml @@ -1,4 +1,4 @@ -<!-- $PostgreSQL: pgsql/doc/src/sgml/datatype.sgml,v 1.171 2006/08/21 16:23:46 tgl Exp $ --> +<!-- $PostgreSQL: pgsql/doc/src/sgml/datatype.sgml,v 1.172 2006/09/07 00:04:48 momjian Exp $ --> <chapter id="datatype"> <title id="datatype-title">Data Types</title> @@ -3295,6 +3295,154 @@ SELECT * FROM pg_attribute </sect1> + <sect1 id="datatype-xml"> + <title><acronym>XML</> Document Support</title> + + <indexterm zone="datatype"> + <primary>xml</primary> + </indexterm> + + <para> + <acronym>XML</> (eXtensible Markup Language) support is not one + capability, but a variety of features supported by a database + system. These capabilities include storage, import/export, + validation, indexing, efficiency of modification, searching, + transforming, and <acronym>XML</> to <acronym>SQL</> mapping. + <productname>PostgreSQL</> supports some but not all of these + <acronym>XML</> capabilities. Future releases of + <productname>PostgreSQL</> will continue to improve <acronym>XML</> + support. For an overview of <acronym>XML</> use in databases, see <ulink + url="http://www.rpbourret.com/xml/XMLAndDatabases.htm"></>. + </para> + + <variablelist> + + <varlistentry> + <term>Storage</term> + <listitem> + + <para> + PostgreSQL does not have a specialized <acronym>XML</> data type. + Users should store <acronym>XML</> documents in ordinary + <type>TEXT</> fields. If you need the document split apart into + its component parts so each element is stored separately, you must + use a middle-ware solution to do that, but once done, the data + becomes relational and has to be processed accordingly. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term>Import/Export</term> + <listitem> + + <para> + There is no facility for mapping <acronym>XML</> to relational + tables. An external tool must be used for this. One simple way to + export <acronym>XML</> is to use <application>psql</> in + <acronym>HTML</> mode (<literal>\pset format html</>), and convert + the <acronym>XHTML</> output to XML using an external tool. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term>Validation</term> + <listitem> + + <para> + <filename>/contrib/xml2</> has a function called + <function>xml_valid()</> that can be used in a <literal>CHECK</> + constraint to enforce that a field contains valid <acronym>XML</>. + It does not support validation against a specific <acronym>XML</> + schema. A server-side language with <acronym>XML</> capabilities + could be used to do schema-specific <acronym>XML</> checks. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term>Indexing</term> + <listitem> + + <para> + <filename>/contrib/xml2</> functions can be used in expression + indexes to index specific <acronym>XML</> fields. To index the + full contents of <acronym>XML</> documents, the full-text indexing + tool <filename>/contrib/tsearch2</> can be used. Of course, + tsearch2 indexes have no <acronym>XML</> awareness so additional + <filename>/contrib/xml2</> checks should be added to queries. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term>Modification</term> + <listitem> + + <para> + If an <command>UPDATE</> does not modify an <acronym>XML</> field, + the <acronym>XML</> data is shared between the old and new rows. + However, if the <command>UPDATE</> modifies an <acronym>XML</> + field, a full modified copy of the <acronym>XML</> field must be + created internally. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term>Searching</term> + <listitem> + + <para> + XPath searches are implemented using <filename>/contrib/xml2</>. + It processes <acronym>XML</> text documents and returns results + based on the requested query. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term>Transforming</term> + <listitem> + + <para> + <filename>/contrib/xml2</> supports <acronym>XSLT</> (XML + Stylesheet Language Transformation). + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term>XML to SQL Mapping</term> + <listitem> + + <para> + This involves converting <acronym>XML</> data to and from + relational structures. <productname>PostgreSQL</> has no internal + support for such mapping, and relies on external tools to do such + conversions. + </para> + </listitem> + </varlistentry> + + <varlistentry> + <term>Missing Features</term> + <listitem> + + <para> + Missing features include XQuery, SQL/XML syntax (ISO/IEC + 9075-14), and an <acronym>XML</> data type optimized for + <acronym>XML</> storage. + + </para> + </listitem> + </varlistentry> + + </variablelist> + + </sect1> + </chapter> <!-- Keep this comment at the end of the file |