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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] [Created] (DERBY-5246) Simplify bytecode generation for concatenation operator
Date Wed, 25 May 2011 10:09:47 GMT
Simplify bytecode generation for concatenation operator
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                 Key: DERBY-5246
                 URL: https://issues.apache.org/jira/browse/DERBY-5246
             Project: Derby
          Issue Type: Improvement
          Components: SQL
    Affects Versions: 10.9.0.0
            Reporter: Knut Anders Hatlen
            Assignee: Knut Anders Hatlen
            Priority: Minor


ConcatenationOperatorNode generates bytecode that ensures the result object is not null before
calling the method that implements the operator. This breaks the pattern used by other operators
(which ensures that the result object is not null inside the method that implements the operator,
not in the generated bytecode), and it unnecessarily complicates the code in BinaryOperatorNode.

The comments indicate that the current approach was chosen to prevent the null check from
happening at execution time, but the generated bytecode does perform the null check at execution
time, so generating byte code for it shouldn't have any real benefit over writing Java code
for it. In general, implementing as much as possible of the execution time code as Java code
is preferred to implementing it directly as bytecode because it's easier to read and debug
Java code, and because the generated bytecode cannot be shared between execution plans and
take more memory.

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