PM38413: ENABLE PERFORMANCE ENHANCEMENT FOR COMPLEX XPATH PREDICATES.

Obtain the fix for this APAR.

APAR status

• Closed as new function.

Error description

• ENABLE PERFORMANCE ENHANCEMENT FOR COMPLEX XPATH PREDICATES.
  

Local fix

• No Work Around
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: DB2 10 for z/OS users who use the XMLQUERY,  *
  *                 XMLEXISTS or XMLTABLE built-in functions.    *
  ****************************************************************
  * PROBLEM DESCRIPTION: In the SQL/XML functions XMLQUERY,      *
  *                      XMLEXISTS and XMLTABLE, when an XPath   *
  *                      predicate is a complex predicate using  *
  *                      XQuery boolean operators "and" and      *
  *                      "or", DB2 does not use an optimum       *
  *                      algorithm to scan the XML document,     *
  *                      therefore, the query performance        *
  *                      for these SQL/XML functions is          *
  *                      not optimized.                          *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  DB2 is modified to enable the support of an improved scan
  algorithm when the XPath predicate uses XQuery boolean
  operator "and" and "or".  In particular, DB2 allows the use of
  new scan algorithm for two types of complex XPath predicates.
  
  1. Conjunctive Normal Form (CNF) : the predicate is a
  conjunction of clauses, where each clause is a disjunction
  of a simple predicate.
  
  2. Disjunctive Normal Form (DNF) : the predicate is a
  disjunction of clauses, where each clause is a conjunction
  of a simple predicate.
  
  For example, the following XPath expressions fall into the
  above two categories, and hence the query performance would be
  improved.
  
  /a/b  (c = 5 or d > 1) and (e = "ABC" or f < 2 or g = 1)
  /a/b  (c = 5 and d >1) or (e = "ABC" and f <2 and g = 1)
  /a/b  c = 5 or d > 1 or e = "ABC"
  
  Additional keywords: SQLXML  SQLPERFORMANCE
  

Problem conclusion

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

  UK71130

Modules/Macros

• DSNXQXQ2 DSNX5XNM
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RA10 PSY UK71130

     UP11/09/08 P F109

Fix is available

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