73 lines
4.7 KiB
HTML
73 lines
4.7 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html lang="en-us" xml:lang="en-us">
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<meta name="DC.Title" content="Restrictions on Java user-defined functions" />
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<meta name="abstract" content="These restrictions apply to Java user-defined functions (UDFs)." />
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<meta name="description" content="These restrictions apply to Java user-defined functions (UDFs)." />
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<meta name="copyright" content="(C) Copyright IBM Corporation 2006" />
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Restrictions on Java user-defined functions</title>
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</head>
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<body id="udfrestr"><a name="udfrestr"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Restrictions on Java user-defined functions</h1>
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<div><p>These restrictions apply to Java™ user-defined functions (UDFs).</p>
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<p> </p>
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<ul><li>A Java UDF
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should not create additional threads. An additional thread may be created
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in a job only if the job is multithread capable. Since it cannot be guaranteed
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that a job that calls an SQL stored procedure is multithread capable, a Java stored
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procedure should not create additional threads.</li>
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<li>The complete name of the Java stored procedure defined to the database
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is limited to 279 characters. This limit is a consequence of the EXTERNAL_NAME
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column, which has a maximum width of 279 characters.</li>
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<li>Adopted authority cannot be used to access Java class files.</li>
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<li>A Java UDF
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always uses the latest version of the JDK that is installed on the system.</li>
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<li>Since Blob and Clob classes reside in both the java.sql and com.ibm.db2.app
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packages, the programmer must use the entire name of these classes if both
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classes are used in the same program. The program must ensure that the Blob
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and Clob classes from the com.ibm.db2.app are used as the parameters passed
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to the stored procedure.</li>
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<li>Like sourced functions, when a Java UDF is created, a service program in
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the library is used to store the function definition. The name of the service
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program is generated by the system and can be found in the job log of the
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job that created the function. If this object is saved and then restored to
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another system, then the function definition is restored. If a Java UDF
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is to be moved from one system to another, you are responsible for moving
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the service program that contains the function definition as well as the integrated
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file system file that contains the Java class.</li>
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<li>A Java UDF
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cannot set the properties (for example, system naming) of the JDBC connection
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that is used to connect to the database. The default JDBC connection properties
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are always used, except when prefetching is disabled.</li>
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</ul>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="writeudf.htm" title="A Java scalar function returns one value from a Java program to the database. For example, a scalar function could be created that returns the sum of two numbers.">Java user-defined scalar functions</a></div>
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</div>
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<div class="relconcepts"><strong>Related concepts</strong><br />
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<div><a href="udftable.htm" title="DB2 provides the ability for a function to return a table. This is useful for exposing information from outside the database to the database in table form. For example, a table can be created that exposes the properties set in the Java virtual machine (JVM) used for Java stored procedures and Java UDFs (both table and scalar).">Java user-defined table functions</a></div>
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</div>
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</div>
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</body>
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</html>
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