I'm getting these xml files from a vendor, and it's a wrapper of NITF (news) schema and the http://www.xmlnews.org/namespaces/meta# news metadata schema (from Space 1999!)

Unfortunately, they don't declare any namespaces at all on the outer document. This is what they give us:

<?xml version="1.0"?>
<xn:Resource xmlns:xn="http://www.xmlnews.org/namespaces/meta#">...</xn:Resource>

I was trying to see if I could improve throughput by creating an xml schema collection and parsing it typed, but the lack of any namespace declaration in the xml text is tripping me up.

I've tried putting

;WITH XMLNAMESPACES (default 'http://iptc.org/std/NITF/2006-10-18/')
SELECT CAST(rawXml as XML(NitfSchemaCollection))

but it doesn't like it (XML Validation: Declaration not found for element 'document' exception).

I even tried using ;WITH XMLNAMESPACES to get the raw xml parsed into an XML type and then casting it to XML(NitfSchemaCollection), but same problem.

So my questions are:

  1. short of re-writing the incoming xml documents from the vendor is there any way to get the xml schema collection applied to the parsing?


  1. Would parsing typed yield enough performance enhancement to make it pursuing further?

We're currently on Sql Server 2008 sp4 but I could try it on a newer instance if that might change something.

EDIT: Here's a sample document. Both the nitf and xn:Resource nodes conform to two very old newswire service serialization standards. For my schema collection I added both, and tweaked the nitf one to add the document node, which is non-standard. The schema are lengthy for a post but I can add them if anyone is interested.

<?xml version="1.0"?>
    <title>First World Problems: 'Should I cancel my Easter holiday and charter a superyacht to escape coronavirus?'</title>
        <hl1>First World Problems: 'Should I cancel my Easter holiday and charter a superyacht to escape coronavirus?'</hl1>
        <bytag>By Caroline White</bytag>
        <distributor>Telegraph Group</distributor>
    <p><em>'I am thinking of cancelling my Easter holiday and chartering a yacht to whisk my immediate family off to sea. The idea is that we can still enjoy the trip of a lifetime without risking contracting the coronavirus. How would you recommend proceeding?'</em></p>
    <p>If you’ve got the wallet for it, a superyacht charter offers the most luxurious seclusion on the planet – and like the hand sanitiser aisle in Boots, you’re not the first to think of it. Some brokers anticipate an uptick in superyacht sales, as UHNWI look to create safe havens, and wealthy holidaymakers are likely to follow suit. So get moving.</p>
    <p>The first step is to recruit a charter broker – try Fraser, Burgess, YPI or <org value="ACORN:3601037911" idsrc="xmltag.org" >Camper &amp; Nicholsons</org>. They will gauge your budget, preferences and read your personality (are you too formal for that laid-back Aussie captain; are you too wild for that silver-service English crew) then come back to you with a bespoke selection of options. The next step is a rather blissful journey through yacht brochures. Then there are the itineraries to flick through: beach barbeques, diving days and suppers under the stars…</p>
    ...blah blah blah...
    <p><em><em>If you have a question for any of our Telegraph Luxury experts, on any topic, please email <a href="http://mailto:firstworldproblems@telegraph.co.uk/">firstworldproblems@telegraph.co.uk</a></em></em></p>
    <p><em>Last week on First World Problems</em></p>
    <p><a href="https://www.telegraph.co.uk/luxury/womens-style/first-world-problems-expensive-blonde-highlights-mayfair-salon/">First World Problems: 'Are expensive highlights at a Mayfair salon worth the price-and the journey?'</a></p>
    <p><em><em>Sign up for the <a href="https://www.telegraph.co.uk/newsletters/Luxury/">Telegraph Luxury newsletter</a> for your weekly dose of exquisite taste and expert opinion.</em></em></p>
<xn:Resource xmlns:xn="http://www.xmlnews.org/namespaces/meta#">
    <xn:providerName>Telegraph Group</xn:providerName>
    <xn:serviceName>Telegraph Online</xn:serviceName>
    <xn:title>First World Problems: 'Should I cancel my Easter holiday and charter a superyacht to escape coronavirus?'</xn:title>
    <xn:vendorData>WAVO:Publish Reason=CORRECTED</xn:vendorData>
    <xn:vendorData>AMX:Publish Reason=CORRECTED</xn:vendorData>
    <xn:vendorData>AMX:Headline Only=FALSE</xn:vendorData>
    <xn:vendorData>AMX:Special Code=PS/p.TELEGR__</xn:vendorData>
    <xn:vendorData>AMX:Special Code=PS/s.ONLINE__</xn:vendorData>
    <xn:copyright>Copyright © 2020 Telegraph.co.ukk. All rights reserved</xn:copyright>
    <!-- Entity Extractor -->
    <!-- Classifier -->
    <xn:vendorData>AMX:Special Code=PT/updated</xn:vendorData>
    <!-- Rules -->
    <xn:vendorData>AMX:Special Code=TL/americas#7#70#50</xn:vendorData>
    <xn:vendorData>AMX:Special Code=TL/LOC#7#50#70</xn:vendorData>
    <xn:vendorData>AMX:Special Code=TT/TOPIC#5#50#50</xn:vendorData>
    <xn:vendorData>AMX:Special Code=TT/transport#5#50#50</xn:vendorData>

Our processing has to parse these documents, then we're trying to normalize out a number of the meta data attributes to various tables and columns.

Just parsing unknown xml, I presume Sql Server has to start with a blank name table for every document parsed; I figured a typed xml column starts with a known vocabulary and should be faster. Plus the hope was the xquery would be faster as well.

Here's an example of the queries we do in processing:

;WITH XMLNAMESPACES ('http://www.xmlnews.org/namespaces/meta#' AS xn)
Insert Into dbo.NewsStory
Select NewsID,provider,service,
    CASE When provider='AMSPIDER' and Service='ACBJ' and PublicationAbbrev='web.site' Then dbo.fnGetSpiderPubAbbrev(PublicationAbbrev_Spider) Else PublicationAbbrev End As PublicationAbbrev,
    Title, PublishDate, AMXReceivedTime, AllowedReleaseTime,ParsedDate,DateLine, Description, [Language], PublishReason, IsAlert, IsHeadLine, IsTemporary, Copyright
    From (
        Select  X.NewsID, 
            replace(RIGHT(RS.c.value('(./xn:vendorData[substring((./text())[1],1,22)="AMX:Special Code=PS/p."]/text())[1]', 'VARCHAR(50)'),8)   , '_', '') as provider, 
            replace(RIGHT(RS.c.value('(./xn:vendorData[substring((./text())[1],1,22)="AMX:Special Code=PS/s."]/text())[1]', 'VARCHAR(50)'),8)   , '_', '') as service,
             CONVERT(NVARCHAR(max),RS.c.query('xn:vendorData'))) as PublicationAbbrev,
            replace(RS.c.value('(./xn:vendorData[substring((./text())[1],1,11)="AMX:Credit="]/text())[1]', 'VARCHAR(200)'),'AMX:Credit=', '')  as PublicationAbbrev_Spider,
            RS.c.value('(./xn:title/text())[1]', 'VARCHAR(200)') AS Title,
      CONVERT(DATETIME,REPLACE(LEFT(RS.c.value('(./xn:publicationTime/text())[1]', 'VARCHAR(50)'),19),'T',' ')) AS PublishDate,
        CONVERT(DATETIME,REPLACE(LEFT(RS.c.value('(./xn:receivedTime/text())[1]', 'VARCHAR(50)'),19),'T',' ')) AS AMXReceivedTime,
        CONVERT(DATETIME,REPLACE(LEFT(RS.c.value('(./xn:releaseTime/text())[1]', 'VARCHAR(50)'),19),'T',' ')) AS AllowedReleaseTime, getdate() as ParsedDate,
        RS.c.value('(./xn:dateline/text())[1]', 'VARCHAR(200)') AS DateLine,
        RS.c.value('(./xn:description/text())[1]', 'VARCHAR(2000)') AS Description,
        RS.c.value('(./xn:language/text())[1]', 'VARCHAR(10)') AS [Language],
        LTRIM(SUBSTRING(RS.c.value('(./xn:vendorData[substring((.)[1],1,19)="AMX:Publish Reason="])[1]','VARCHAR(45)'),20,25)) AS PublishReason,
       CASE LTRIM(SUBSTRING(RS.c.value('(./xn:vendorData[substring((./text())[1],1,10)="AMX:Alert="]/text())[1]','VARCHAR(45)'),11,10)) WHEN 'FALSE' THEN 0 ELSE 1 END AS IsAlert,
       CASE LTRIM(SUBSTRING(RS.c.value('(./xn:vendorData[substring((./text())[1],1,18)="AMX:Headline Only="]/text())[1]','VARCHAR(45)'),19,10)) WHEN 'FALSE' THEN 0 ELSE 1 END AS IsHeadLine,
       CASE LTRIM(SUBSTRING(RS.c.value('(./xn:vendorData[substring((./text())[1],1,14)="AMX:Temporary="]/text())[1]','VARCHAR(45)'),15,10)) WHEN 'FALSE' THEN 0 ELSE 1 END AS IsTemporary,
       RS.c.value('(./xn:copyright/text())[1]', 'VARCHAR(1000)')AS Copyright
       From @XmlFileTable X CROSS APPLY AMXFile.nodes('/document/xn:Resource') RS(c)
    ) A

The schema collection comes from the NITF source (https://www.iptc.org/std/NITF/3.6/specification/nitf-3-6.xsd) and the xmlnews dtd (http://www.xmlnews.org/dtds/xmlnews-meta-dtd.zip).

I used Visual Studio to convert the xmlnews dtd to a schema and used that to seed NitfSchemaCollection.

Then I tweaked the NITF schema to

  • remove the include (apparently a small subset for Ruby that I didn't need)

  • added to the header

     ... xmlns:xn="http://www.xmlnews.org/namespaces/meta#">

    <import namespace="http://www.xmlnews.org/namespaces/meta#" />

  • added a document element just above the nitf element declaration, to match what the vendor is shipping to us. e.g.

    <element name="document"> <complexType> <sequence> <element ref="nitf:nitf" minOccurs="1" maxOccurs="1" /> <element ref="xn:Resource" minOccurs="1" maxOccurs="1" /> </sequence> </complexType> </element>

Each document has only 1 nitf node and 1 xn:Resource node, but there can be many instances of the child nodes under xn:Resource.

  • Can't you read it without namespace? dbfiddle.uk/… – McNets Jul 21 '20 at 21:45
  • I can read it without a namespace, but the xml parsing and xquery operations were quite slow. I'd hoped to be able to speed them up by adding a schema collection and parsing typed, but then I hit this roadblock. I implemented some other suggestions particular to the xquery (e.g. instead of getting the value of (.), use (./text())[1]) and while that seemed to help a little, I was looking for more performance improvement. – user1664043 Jul 21 '20 at 21:57
  • 1
    What is the datatype of rawxml and what does NitfSchemaCollection look like? – Mikael Eriksson Jul 22 '20 at 6:10
  • 1
    And if you want some help with optimizing the query you should provide it with some sample data and expected result. – Mikael Eriksson Jul 22 '20 at 7:19
  • You could add the schema with pastebin. I would like to try if it is faster with a schema. I have yet to find a case where it is so but you never know. I also would like to know if there can be multiple xn:Resource nodes in one document (row in @XmlFileTable). And if so, how many (ball park figure). – Mikael Eriksson Jul 22 '20 at 16:20

The part of the XML you are parsing is not constricted by a schema but by a DTD so you can't use a schema collation to make the parsing by SQL Server any different. That said, I have not seen a case yet where a schema is helpful in the scenario where you are shredding XML documents to tables, and there is adding the overhead of validating the XML against the schema to that.

There are some things you can do in the query to make it more efficient.

In the query below I changed the handling of dates, moved the text() in predicates before the predicate and use . in the predicate and using exist() where you are checking for boolean values.

Note that what happened to me in my tests was that the rewrite did not go parallell so when comparing performance keep that in mind. You might like that it only uses one thread in a busy server or you might want to use everything you have. If you want the query to go parallell you can use a trace flag OPTION(QUERYTRACEON 8649) or if you prefer a serial plan use option (maxdop 1).

So in my tests on SQL Server 2008 the performance of the rewrite is about twice as fast.

Look at what I did here, use it if you like it and test on your data.

with xmlnamespaces ('http://www.xmlnews.org/namespaces/meta#' AS xn)
select replace(right(RS.c.value('(xn:vendorData/text()[substring((.)[1],1,22)="AMX:Special Code=PS/p."])[1]', 'varchar(50)'), 8), '_', '') as provider,
       replace(right(RS.c.value('(xn:vendorData/text()[substring((.)[1],1,22)="AMX:Special Code=PS/s."])[1]', 'varchar(50)'), 8), '_', '') as service,
       convert(nvarchar(max), RS.c.query('xn:vendorData')) as PublicationAbbrev,
       replace(RS.c.value('(xn:vendorData/text()[substring((.)[1],1,11)="AMX:Credit="])[1]', 'VARCHAR(200)'), 'AMX:Credit=', '') as PublicationAbbrev_Spider,
       RS.c.value('(xn:title/text())[1]', 'varchar(200)') as Title,
       convert(datetime, RS.c.value('(xn:publicationTime/text())[1]', 'varchar(19)')) as PublishDate,
       convert(datetime, RS.c.value('(xn:receivedTime/text())[1]', 'varchar(19)')) as AMXReceivedTime,
       convert(datetime, RS.c.value('(xn:releaseTime/text())[1]', 'varchar(19)')) as AllowedReleaseTime,
       getdate() as ParsedDate,
       RS.c.value('(xn:dateline/text())[1]', 'varchar(200)') as DateLine,
       RS.c.value('(xn:description/text())[1]', 'varchar(2000)') as Description,
       RS.c.value('(xn:language/text())[1]', 'varchar(10)') as [Language],
       ltrim(substring(RS.c.value('(./xn:vendorData/text()[substring((.)[1],1,19)="AMX:Publish Reason="])[1]', 'VARCHAR(45)'), 20, 25)) as PublishReason,
       RS.c.exist('xn:vendorData/text()[. = "AMX:Alert=TRUE"]') as IsAlert,
       RS.c.exist('xn:vendorData/text()[. = "AMX:Headline Only=TRUE"]') as IsHeadLine,
       RS.c.exist('xn:vendorData/text()[. = "AMX:Temporary=TRUE"]') as IsTemporary,
       RS.c.value('(xn:copyright/text())[1]', 'varchar(1000)') as Copyright
from @XmlFileTable X
  cross apply AMXFile.nodes('/document/xn:Resource') RS(c);
  • Thank you so much for taking all this time, and for your refinements. I think the most surprising one to me was the datetime columns. I'd just assumed that 'varchar(19)' would result in one of those data truncation errors you'd get trying to jam a too-big string into a column instead of quiet substringing I was re-thinking that whole section and maybe it would be more correct, in general, to take the whole string, convert to datetimeoffset, and then to datetime so I don't lose the timezone information. Probably wouldn't help the performance as much though – user1664043 Jul 23 '20 at 14:11
  • On the dtd front, Visual Studio has a "convert to schema" option which I used to create the schema collection - but then I ran into the source xml being unfortunately constructed. – user1664043 Jul 23 '20 at 14:12
  • @user1664043 I did a test with a schema converted from the DTD and there was no difference at all in performance to query the XML and about 10% slower to load it to the table variable. What I did to make use of the schema was to only load the xn:Resource node to @XmlFileTable. – Mikael Eriksson Jul 23 '20 at 18:34
  • Sorry to be a pest, but what would you expect if I change the table variable to a temp table and add a primary xml index? Would the index help the xquery more than the cost of maintaining the index? – user1664043 Jul 24 '20 at 13:17
  • I would not expect that to be a success but you will never know without testing. Here is a question about performance and XML indexes with a rather lengthy answer that in parts might be interesting for you. – Mikael Eriksson Jul 24 '20 at 15:16

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