Knut Anders Hatlen created DERBY-5989:
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Summary: Stop producing byte code for non-existent qualifiers
Key: DERBY-5989
URL: https://issues.apache.org/jira/browse/DERBY-5989
Project: Derby
Issue Type: Improvement
Components: SQL
Affects Versions: 10.10.0.0
Reporter: Knut Anders Hatlen
Assignee: Knut Anders Hatlen
Priority: Minor
For all result set nodes that have predicate lists, Derby's compiler lays out
byte code for fields to hold qualifiers, and also code to reinitialize the
values in those fields on every execution. It does this even if there are no
qualifiers. See PredicateList.generateQualifiers(). That method does actually
check whether there are qualifiers, and it skips some of the code generation if
there are none. It should be changed so that it skips all the code generation
if there are no qualifiers.
For an example, see the decompiled generated class for a natural join attached
to DERBY-5947:
https://issues.apache.org/jira/secure/attachment/12549514/natural-join-after-3a.txt
That class contains three Qualifier[][] fields:
private Qualifier[][] e1;
private Qualifier[][] e3;
private Qualifier[][] e4;
Only one of them (e4) is ever set to a non-null value. Still, the reinit()
method, which is called on every execution, has code for each of the fields:
protected void reinit() throws StandardException {
BaseActivation.reinitializeQualifiers(e1);
BaseActivation.reinitializeQualifiers(e3);
BaseActivation.reinitializeQualifiers(e4);
}
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