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Result Cache Functions

without comments

I finally got around to cleaning up old contact me messages. One of the messages raises a question about RESULT_CACHE functions. The writer wanted an example implementing both a standalone schema and package RESULT_CACHE function.

The question references a note from the Oracle Database 11g PL/SQL Programming book (on page 322). More or less, that note points out that at the time of writing a RESULT_CACHE function worked as a standalone function but failed inside a package. When you tried it, you raised the following error message:

PLS-00999: Implementation Restriction (may be temporary)

It’s no longer true in Oracle 11gR2, but it was true in Oracle 11gR1. I actually mentioned in a blog entry 4 years ago.

You can implement a schema RESULT_CACHE function like this:

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CREATE OR REPLACE FUNCTION full_name
( pv_first_name   VARCHAR2
, pv_last_name    VARCHAR2 )
RETURN VARCHAR2 RESULT_CACHE IS
BEGIN  
  RETURN pv_first_name || ' ' || pv_last_name;
END full_name;
/

You would call it like this from a query:

SELECT   full_name(c.first_name, c.last_name)
FROM     contact c;

You can declare a published package RESULT_CACHE function like this:

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CREATE OR REPLACE PACKAGE cached_function IS
  FUNCTION full_name
  ( pv_first_name   VARCHAR2
  , pv_last_name    VARCHAR2 )
  RETURN VARCHAR2 RESULT_CACHE;
END cached_function;
/

You would implement the function in a package body like this:

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CREATE OR REPLACE PACKAGE BODY cached_function IS
  FUNCTION full_name
  ( pv_first_name   VARCHAR2
  , pv_last_name    VARCHAR2 )
  RETURN VARCHAR2 RESULT_CACHE IS
  BEGIN  
    RETURN pv_first_name || ' ' || pv_last_name;
  END full_name; 
END cached_function;
/

You would call the package function like this from a query:

SELECT   cached_function.full_name(c.first_name, c.last_name)
FROM     contact c;

I hope this answers the question.

Written by maclochlainn

May 29th, 2012 at 12:31 am

Posted in Oracle,Oracle 11g,pl/sql,Uncategorized

Collaborate 2012 – Day 3

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Virtualization is important and Dave Welch from the House of Brick gave a great presentation of experiences with VMWare and Tier 1 databases. It was a comprehensive presentation, but the white paper was easier to follow. The slides were complete but the volume of information was a lot for an hour presentation. Well worth the time though.

Utah Oracle User Group (UTOUG) announced a call for Fall Symposium papers today. The Fall Symposium will be in Salt Lake City on 9/6/2012. If you’re interested in presenting on Oracle or MySQL, the call for presentations will be open until 6/15/2012.

The conference party was tonight, and it provided some nice orderves and pizza. The theme was a return to 1980s music, and some folks really dressed their parts. You can listen to a short snapshot of the band by clicking the image to launch a small video segment.

I’m looking forward to the APEX Behind the Scenes presentation at 8:30 a.m. tomorrow. When the conference is over, I won’t miss the smoke filled air that we walk through from the Luxor to the Mandalay. It’s really amazing that the complex is more than a mile in length. It runs from the Luxor to the Mandalay South Conference Center.

Written by maclochlainn

April 26th, 2012 at 12:31 am

Posted in Collaborate Conference,MySQL,Oracle,Uncategorized

Java Generics in Oracle

without comments

Somebody posed the question about using a Comparator in the sorting examples provided in this earlier post on Updating Table View Columns (columns using a Varray or Nested Table of a single scalar data type). It seems the individual thought that you can’t use Java Generics inside an Oracle Database 11g’s Java libraries. It’s seems odd since they’ve been around since Java 5.

You can use Generics like those shown in the following example. It builds on explanation from the prior post. If you want to get the whole set of facts click the link above but you should have all the code you need in this post.

An example like this requires you first define a collection of strings in the database. This one uses the following definition:

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CREATE OR REPLACE TYPE stringlist IS TABLE OF VARCHAR2(4000);
/

This creates the Java library source, and line 21 shows the use of Generics in the instantiation of a anonymous Comparator class:

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CREATE OR REPLACE AND COMPILE JAVA SOURCE NAMED "SortList" AS
 
  // Import required classes.
  import java.io.*;
  import java.security.AccessControlException;
  import java.sql.*;
  import java.util.Arrays;
  import java.util.Comparator;
  import oracle.sql.driver.*;
  import oracle.sql.ArrayDescriptor;
  import oracle.sql.ARRAY;
 
  // Define class.
  public class Sorting {
    public static ARRAY sortTitleCaseList(oracle.sql.ARRAY list) throws SQLException, AccessControlException {
 
    // Convert Oracle data type to Java data type.
    String[] unsorted = (String[])list.getArray();
 
    // Sort elements.
    Arrays.sort(unsorted, new Comparator<String>() {
      public int compare(String s1, String s2) {
 
      // Declare a sorting key integer for the return value.
      int sortKey;
 
      // Check if lowercase words match and sort on first letter only.
      if (s1.toLowerCase().compareTo(s2.toLowerCase()) == 0)
         sortKey = s1.substring(0,1).compareTo(s2.substring(0,1));
      else
        sortKey = s1.toLowerCase().compareTo(s2.toLowerCase());
 
      // Return the sorting index.
      return sortKey; }});
 
      // Define a connection (this is for Oracle 11g).
      Connection conn = DriverManager.getConnection("jdbc:default:connection:");
 
      // Declare a mapping to the schema-level SQL collection type.
      ArrayDescriptor arrayDescriptor = new ArrayDescriptor("STRINGLIST",conn);
 
      // Translate the Java String{} to the Oracle SQL collection type.
      ARRAY sorted = new ARRAY(arrayDescriptor,conn,((Object[])unsorted));
 
      // Return the sorted list.
      return sorted; }
  }
/

The PL/SQL wrapper for this class would be:

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CREATE OR REPLACE FUNCTION sortTitleCaseList(list STRINGLIST) RETURN STRINGLIST IS
LANGUAGE JAVA
NAME 'Sorting.sortNaturalCaseList(oracle.sql.ARRAY) return oracle.sql.ARRAY';
/

You can test the code with the following query:

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SELECT column_value
FROM TABLE(sortTitleCaseList(stringlist('Oranges','apples','Apples','Bananas','Apricots','apricots')));

It sorts the strings based on a title case sort, like:

COLUMN_VALUE
------------------------
Apples
apples
Apricots
apricots
Bananas
Oranges
 
6 rows selected.

If you want a quick example of a Generic Collection sort operation outside of the database, here a sample file.

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// Import required classes.
import java.util.Arrays;
import java.util.Comparator;
 
/**
 * An example of using a Comparator sort.
 */
public class SortStaticString {
 
  /*
   * Sort the instance array.
   */
  public static String[] sortTitleCaseList(String[] list) {
 
    // Sort elements by title case.
    Arrays.sort(list, new Comparator<String>() {
      public int compare(String s1, String s2) {
 
        // Declare a sorting key integer for the return value.
        int sortKey;
 
        // Check if lowercase words match and sort on first letter only.
        if (s1.toLowerCase().compareTo(s2.toLowerCase()) == 0)
          sortKey = s1.substring(0,1).compareTo(s2.substring(0,1));
        else
          sortKey = s1.toLowerCase().compareTo(s2.toLowerCase());
 
        // Return the sorting index.
        return sortKey; }});
 
    // Return the sorted Index.     
    return list;
  }
 
  /*
   * Test case.
   */
  public static void main(String[] args) {
 
    // Construct and instance and apply sort method.     
    args = SortStaticString.sortTitleCaseList(args);
 
    // Print the title case sorted list.
    for (int i = 0; i < args.length; i++) {
      System.out.println(args[i]); }
  }
}

You would call the SortStaticString class as follows:

java SortStaticString apples Oranges Pears Apples orange Grapefruit

I hope this helps the interested party and any others looking for a sample file. 😉

Written by maclochlainn

January 11th, 2012 at 12:49 am

Posted in Java,Oracle,Oracle 11g,Uncategorized

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