Chunhui Shi created DRILL-4777:
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Summary: Fuse generated code to reduce code size and gain
performance improvement
Key: DRILL-4777
URL: https://issues.apache.org/jira/browse/DRILL-4777
Project: Apache Drill
Issue Type: Bug
Reporter: Chunhui Shi
Drill generates code for operators, compile the classes and load them on the
fly of a query. However, in large query cases, the generated code will become
hundreds KB or could be even bigger. We have seen multiple issues reported when
generated code is too big either due to Java's size limit to one method or
degrated performance of compiling or executing. Also when I looked at JIT
optimization logs, there are many complaining about 'hot method too big'
Some measures can be considered to reduce the code size, such as,
1) For now Drill embed function calls' code directly into generated code, this
make one line function call to become 5-10 lines code in generated java
classes. If we inject these functions as a private functions of the classes and
directly call them in main function body, this could reduce code size while the
cost of function call can be erased by JIT inline optimization.
2) Drill generate one variable for each column, if the column number became
dozens to one hundred, the code will be redundant, we could consider using an
array to store the value vectors and loop on top of it so the code size will be
reduced even more.
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