Category: XMLDB
October 16

XMLDB Performance: Collection Iterator Pickler Fetch

Nowadays, this “Collection Iterator Pickler Fetch” output in an explain plan is less and less seen as the XML database functionality becomes more and more stronger in re-writing statements. Alas, I got one, again.

SQL> xquery
  2   let $auction := ora:view("XM_TAB") return
  3   count(
  4     for $i in $auction/site/closed_auctions/closed_auction
  5     where $i/price/text() >= 40
  6     return $i/price
  7*  )

Result Sequence
---------------
6539

Execution Plan
----------------------------------------------------------
Plan hash value: 4083502163

-----------------------------------------------------------------------------------------------------------
| Id  | Operation                         | Name                  | Rows  | Bytes | Cost (%CPU)| Time     |
-----------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT                  |                       |  8168 | 16336 |    29   (0)| 00:00:01 |
|   1 |  COLLECTION ITERATOR PICKLER FETCH| XQSEQUENCEFROMXMLTYPE |       |       |            |          |
-----------------------------------------------------------------------------------------------------------

Statistics
----------------------------------------------------------
        143  recursive calls
          0  db block gets
     385537  consistent gets
        119  physical reads
          0  redo size
       1439  bytes sent via SQL*Net to client
        942  bytes received via SQL*Net from client
          6  SQL*Net roundtrips to/from client
      19500  sorts (memory)
          0  sorts (disk)
          1  rows processed
SQL>

I couldn’t find much on the internet about the “collection iterator pickler fetch” (lets call it CIPF for now). These posts from Steve Adams and Tom Kyte shed some light on what is happening.

In the XMLDB realm, I now found two examples of CIPF.

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September 5

XMLDB Performance: Binary XML Storage Models

This post will show you some of the first numbers I collected regarding “Loading XML data”, while making use of different XMLType “physical storage containers”.

I also have done some initial testing with Object Relational XMLType storage, but because this method of storage has many options and extra features, I won’t describe them yet here. This topic is interesting enough to earn its on post.

If you need some background on Oracle XMLType Storage option than have a read through the “Binary-, CLOB, Object Relational Storage” Category option in the menu, the Oracle XMLDB Developers Manual or a short intro via Oracle 11g – XMLType Storage Options.

After having created an environment as described in “XMLDB Performance: Environment, Set-up, Procedure“, the following results were gathered by me while keeping values constant, for example the values for “connection.xml“, as described in the “XMLDB Performance: Environment, Set-up, Procedure” . Only the WIKI_STAGE create statements are different.

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September 5

XMLDB Performance: Environment, Set-up, Procedure

There has some time past since my last update on my XMLDB Performance, tuning, adventure. As you maybe have read, I had my problems to set-up a decent test environment and loading XML data. I am testing with an Mediawiki XML dumpfile. If there is a problem or a side effect to notice than I have a big chance that it will show up if not only by the size of this Mediawiki XML dumpfile. The Mediawiki XML dumpfile contains, when I downloaded it, almost 8 million records and has a file size on Windows NT NFS of 17,4 Gigabyte.

Loading this data via the procedures described in my posts, “HOWTO: Load Really Big XML Files” and “Setting Up an XMLDB Performance “Baseline” Environment (Part 02)” dealt with some of the issues I encountered to realize controllable testing set-up. Loading this amount of XML data will take some time.

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