Xml select query xpath is slow - sql

Question

My XML structure:
<Items>
<Item>
<guid>FC550573-7171-997F-752D-8D65590CBFD6</guid>
<Objects>
<Object>
<type>0</type>
<guid>E10D9DA9-2C8D-8024-2F07-DF21395811BF</guid>
</Object>
<Object>
<type>0</type>
<guid>D8338400-35C7-781E-A039-C0FDDF80714A</guid>
</Object>
</Objects>
</Item>
</Items>
When filling the Objects Table:
CREATE TABLE [dbo].[Objects](
[item_guid] [varchar](36) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL,
[type] [int] NOT NULL,
[guid] [varchar](36) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL
) ON [PRIMARY]
Using the Query:
INSERT INTO [dbname].[dbo].[Objects]
([item_guid]
,[type]
,[guid])
SELECT
X.source.query('../../guid').value('.','VARCHAR(36)') as item_guid,
X.source.query('type').value('.','INT') as type,
X.source.query('guid').value('.','VARCHAR(36)') as guid
FROM(
Select xmldata from XmlFiles where fullpath=#fp
) AS T(x)
CROSS APPLY x.nodes('Items/Item/Objects/Object') As X(source)
This line is making the query VERY slow:
X.source.query('../../guid').value('.','VARCHAR(36)') as item_guid
What is the proper approach here?

Answer 1

Using /text() to get the value is good for performance on untyped XML. It can also be bad to use the parent axis ../.. (as #marc_s suggested).
Here is a version with a extra cross apply and /text() to get the values.
Try this:
select T2.N.value('(guid/text())[1]', 'uniqueidentifier') as item_guid,
T3.N.value('(type/text())[1]', 'int') as type,
T3.N.value('(guid/text())[1]', 'uniqueidentifier') as guid
from (SELECT xmldata FROM dbo.XmlFiles WHERE fullpath = #fp) as T1(N)
cross apply T1.N.nodes('Items/Item') as T2(N)
cross apply T2.N.nodes('Objects/Object') as T3(N)
You have to be the judge which query is the fastest for you.

Answer 2

I just want to add, in case anybody else runs across this, that adding the following option makes a huge difference.
OPTION (OPTIMIZE FOR (#testXml = NULL))
If you'd like to test this yourself, here is a short test script I was running. Just look at the estimated subtree cost between these.
declare #testXml xml set #testXml = '<filters><filter name="test name" type="GREATERTHAN">1</filter><filter name="CLAIMID" type="GREATERTHAN">1</filter></filters>'
select x.value('#name','nvarchar(100) ') filtername,
x.value('.','nvarchar(200)')filtervalue,
x.value('#type','nvarchar(50) ') filtertype
from #testXml.nodes('/filters/filter') as ref(x)
--vs...
select x.value('#name','nvarchar(100) ') filtername,
x.value('.','nvarchar(200)')filtervalue,
x.value('#type','nvarchar(50) ') filtertype
from #testXml.nodes('/filters/filter') as ref(x)
OPTION (OPTIMIZE FOR (#testXml = NULL))

Answer 3

Try this,
We will create a temp table variable for store this xml values & insert to corresponding table Objects
//..Xml value to temp variable
Declare #x xml ='<Items><Item><guid>FC550573-7171-997F-752D-8D65590CBFD6</guid><Objects><Object>
<type>0</type><guid>E10D9DA9-2C8D-8024-2F07-DF21395811BF</guid></Object><Object>
<type>0</type><guid>D8338400-35C7-781E-A039-C0FDDF80714A</guid></Object></Objects>
</Item></Items>';
Declare #Temp_Tbl table (RowId int identity, item_guid nvarchar(36), [type] int, [guid] nvarchar(36));
Insert into #Temp_Tbl SELECT #x.value('(/Items/Item/guid)[1]', 'nvarchar(36)'),
Cont.value('(type)[1]', 'int'), Cont.value('(guid)[1]', 'nvarchar(36)')
FROM #x.nodes('/Items/Item/Objects/Object') AS Obj(Cont);
INSERT INTO [dbo].[Objects] Select item_guid,[type],[guid] from #Temp_Tbl;