Expression parser performance optimization
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Key: CAY-1667
URL: https://issues.apache.org/jira/browse/CAY-1667
Project: Cayenne
Issue Type: Improvement
Components: Core Library
Affects Versions: 3.1M3
Reporter: Andrus Adamchik
Assignee: Andrus Adamchik
Inspecting some profiling data from a customer I see an inefficiency inside
Expression.fromString. It was actually discovered inside Ordering class, that
compiles path string on demand, so it affects even the queries that do not use
'fromString', as well Orderings created for in-memory sorting. There are 2
culprits in JavaCharStream that is generated by javaCC (although JavaCharStream
is not a part of the parser, so we can probaby change the code on top of the
generated class) :
1. JavaCharStream.fillBuff() has throw new java.io.IOException(); that is
caught right in that same method (!!!) Throwable.fillStackTrace() shows as a
"hot spot" in the profile. There should be a better way to handle if/else
condition :)
2. Expression.fromString -> new ExpressionParser(Reader) -> new
JavaCharStream(Reader, int startline, int startcolumn)
JavaCharStream constructor is heavy and shows as a hotspot. For one thing it
creates 4 int/char buffers with size of 4096 each. I don't think we have such
long expressions ever, and don't need all this memory. Moreover we can probably
guess the max needed buffer size from the original String length. My guess is
that most expressions are under 100-300 chars. Certainly true for the orderings.
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