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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