DB2 Version 10.1 for Linux, UNIX, and Windows

Performance improved for certain XML queries

In DB2® V10.1, the DB2 server has been optimized to improve performance for certain commonly used queries, such as those that use the XMLTABLE function.

Examples of queries that might show faster response are as follows:

Queries that use the XMLTABLE function. For example:

SELECT T.* FROM TEST, 
   XMLTABLE('$doc/a/b' passing TEST.XMLCOL as "doc" columns
                   c varchar(10) path 'c1/c2/c'
                   d varchar(10) path 'd1/d2/d'
                   e varchar(10) path 'e1/e2/e')  AS T;

Non-linear XQuery queries (with multiple paths, or branches). For example:

xquery for $a in db2-fn:xmlcolumn('XTAB.DOC')/a 
   for $b in $a/b 
   for $c in $a/c 
   return <res>{$b,$c}</res>

Queries with early-out join predicates. An early-out join is a join in which at most one row from the inner table must match a row in the outer table. For example, the following XMLTABLE query has an early-out join on a row generator:

SELECT stat, gen FROM custacc,
     XMLTABLE('$CADOC/Customer [DateOfBirth >= xs:date("1910-01-01")
                              and BankingInfo/PremiumCustomer = "No"] '
     COLUMNS
       GEN   VARCHAR(20) PATH 'Gender',
       Nationality VARCHAR(20) PATH 'Customer/Nationality,
       STAT  VARCHAR(20) PATH 'BankingInfo/CustomerStatus');

The next example has an early out join on the for clause:

xquery for $i in db2-fn:xmlcolumn('T.XMLCOL')/PRODUCT, 
   $j in $i[NAME='5Z761']//PRICE 
   return $j

Queries with a parent axis. For example, the following XMLTABLE query has a parent axis that is not on the output step:

    SELECT T.* FROM TEST, 
              XMLTABLE ( '$doc/a/b'  passing TEST.XMLCOL as "doc" columns
                   c varchar(10) path 'c1/c2/c'
                   d varchar(10) path '../d1/d2/d'
                   e varchar(10) path '../../e1/e2/e')  as T

The next example also has a parent axis that is not on the output step:

xquery let $doc := db2-fn:xmlcolumn('T.XMLCOL') return  ($doc/root//a/.. )/b