[DOCS] New XML section for documentation
Here is an new XML section for our SGML documentation. It explains the various XML capabilities, if we support them, and how to use them. Comments? --- XML Document Support XML support is not one capability, but a variety of features supported by a database. These capabilities include storage, import/export, validation, indexing, efficiency of modification, searching, transformating, and XML to SQL mapping. PostgreSQL supports some but not all of these XML capabilities. Future releases of PostgreSQL will continue to improve XML support. Storage --- PostgreSQL stores XML documents as ordinary text documents. It does not split apart XML documents into its component parts and store each element separately. You can use middle-ware solutions to do that, but once done, the data becomes relational and has to be processed accordingly. Import/Export - Because XML documents are stored as normal text documents, they can be imported/exported with little complexity. A simple TEXT field can hold up to 1 gigabyte of text, and large objects are available for larger documents. Validation -- /contrib/xml2 has a function called xml_valid() that can be used in a CHECK constraint to enforce that a field contains valid XML. It does not support validation against a specific XML schema. A server-side language with XML capabilities could be used to do schema-specific XML checks. Indexing Because XML documents are stored as text, full-text indexing tool /contrib/tsearch2 can be used to index XML documents. Of course, the searches are text searches, with no XML awareness, but tsearch2 can be used with other XML capabilities to dramatically reduce the amount of data processed at the XML level. Modification If an UPDATE does not modify an XML field, the XML data is shared between the old and new rows. However, if the UPDATE modifies a XML field, a full modified copy of the XML field must be created internally. Searching - XPath searches are implemented using /contrib/xml2. It processes XML text documents and returns results based on the requested query. Transforming /contrib/xml2 supports XSL transformations. XML to SQL Mapping --- This involves converting XML data to and from relational structures. PostgreSQL has no internal support for such mapping, and relies on external tools to do such conversions. Missing Features o XQuery o SQL/XML syntax (ISO/IEC 9075-14) o XML data type optimized for XML storage See also http://www.rpbourret.com/xml/XMLAndDatabases.htm -- Bruce Momjian [EMAIL PROTECTED] EnterpriseDBhttp://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. + ---(end of broadcast)--- TIP 5: don't forget to increase your free space map settings
Re: [DOCS] [HACKERS] New XML section for documentation
On Fri, Aug 25, 2006 at 07:46:57PM -0400, Bruce Momjian wrote: > Here is an new XML section for our SGML documentation. It explains > the various XML capabilities, if we support them, and how to use > them. > > Comments? This looks hauntingly similar to Peter's presentation at the conference. :) I'd add a http://wiscorp.com/SQLStandards.html to the reference section. Speaking of other parts of the SQL:2003 standard, how about one section each that mentions them? There's Part 4: SQL/PSM (Persistent Stored Modules) Part 9: SQL/MED (Management of External Data) (my favorite) Part 10: SQL/OLB (Object Language Binding) Part 11: SQL/Schemata Part 13: SQL/JRT (Java Routines and Types) Cheers, D -- David Fetter <[EMAIL PROTECTED]> http://fetter.org/ phone: +1 415 235 3778AIM: dfetter666 Skype: davidfetter Remember to vote! ---(end of broadcast)--- TIP 4: Have you searched our list archives? http://archives.postgresql.org
Re: [DOCS] [HACKERS] New XML section for documentation
David Fetter wrote: > On Fri, Aug 25, 2006 at 07:46:57PM -0400, Bruce Momjian wrote: > > Here is an new XML section for our SGML documentation. It explains > > the various XML capabilities, if we support them, and how to use > > them. > > > > Comments? > > This looks hauntingly similar to Peter's presentation at the I used the XML/SQL and validation part from his talk, but the rest was from earlier email discussions. > conference. :) I'd add a http://wiscorp.com/SQLStandards.html to the This seems to be the best URL, but it seems too detailed: http://wiscorp.com/H2-2005-197-SC32N1293-WG3_Presentation_for_SC32_20050418.pdf > reference section. > > Speaking of other parts of the SQL:2003 standard, how about one > section each that mentions them? There's > > Part 4: SQL/PSM (Persistent Stored Modules) > Part 9: SQL/MED (Management of External Data) (my favorite) > Part 10: SQL/OLB (Object Language Binding) > Part 11: SQL/Schemata > Part 13: SQL/JRT (Java Routines and Types) I don't know anything about them. -- Bruce Momjian [EMAIL PROTECTED] EnterpriseDBhttp://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. + ---(end of broadcast)--- TIP 2: Don't 'kill -9' the postmaster
Re: [DOCS] [HACKERS] New XML section for documentation
Euler Taveira de Oliveira wrote: > Bruce Momjian wrote: > > > Here is an new XML section for our SGML documentation. It explains the > > various XML capabilities, if we support them, and how to use them. > > > > Comments? > > > +1. Users often ask this in the mailing lists. Where are you want to > put this? I'll suggest: FAQ. What do you all think? Our main documentation. Once it is there, people will find it rather than on the FAQ. > > Missing Features > > > > o XQuery > > o SQL/XML syntax (ISO/IEC 9075-14) > > o XML data type optimized for XML storage > > > Another section in TODO? Perhaps, yea. -- Bruce Momjian [EMAIL PROTECTED] EnterpriseDBhttp://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. + ---(end of broadcast)--- TIP 5: don't forget to increase your free space map settings
Re: [DOCS] [HACKERS] New XML section for documentation
Bruce Momjian wrote: > Here is an new XML section for our SGML documentation. It explains the > various XML capabilities, if we support them, and how to use them. > > Comments? > +1. Users often ask this in the mailing lists. Where are you want to put this? I'll suggest: FAQ. What do you all think? > Missing Features > > o XQuery > o SQL/XML syntax (ISO/IEC 9075-14) > o XML data type optimized for XML storage > Another section in TODO? -- Euler Taveira de Oliveira http://www.timbira.com/ ---(end of broadcast)--- TIP 4: Have you searched our list archives? http://archives.postgresql.org
Re: [DOCS] New XML section for documentation
> Indexing > > Because XML documents are stored as text, full-text indexing tool > /contrib/tsearch2 can be used to index XML documents. Of > course, the searches are text searches, with no XML > awareness, but tsearch2 can be used with other XML > capabilities to dramatically reduce the amount of data > processed at the XML level. You can also use a functional index and /contrib/xml2 to do limited XPath indexing. (Can't make it "subtree-aware" for example, unless you are willing to change your queries, but you can index specific xpath nodes). //Magnus ---(end of broadcast)--- TIP 5: don't forget to increase your free space map settings
Re: [DOCS] New XML section for documentation
Bruce Momjian wrote: > XML Document Support > > XML support is not one capability, but a variety of features > supported by a database. database system > Storage > --- > PostgreSQL stores XML documents as ordinary text documents. It is "possible" to do that, but this sounds like it's done automatically or implicitly. Maybe: "PostgreSQL does not have a specialized XML data type. The recommended way is to store XML documents as text." > Import/Export > - > Because XML documents are stored as normal text documents, they can > be imported/exported with little complexity. Import/export refers to exporting schema data with XML decorations. Of course you can export column data trivially, but that's not what this is about. > Validation > -- > /contrib/xml2 has a function called xml_valid() that can be used in > a CHECK constraint to enforce that a field contains valid XML. It > does not support validation against a specific XML schema. Then this is not validation but only checking for well-formedness. The xml2 README says so, in fact. > Indexing > I think the expression index capability combined with contrib/xml2 is more relevant here than the full-text search capability. > Transforming > > /contrib/xml2 supports XSL transformations. That's XSLT. > XML to SQL Mapping > --- > This involves converting XML data to and from relational structures. > PostgreSQL has no internal support for such mapping, and relies on > external tools to do such conversions. Are there instances of such tools? -- Peter Eisentraut http://developer.postgresql.org/~petere/ ---(end of broadcast)--- TIP 6: explain analyze is your friend
