Github user jinfengni commented on a diff in the pull request:
https://github.com/apache/drill/pull/818#discussion_r117573874
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/expr/ClassGenerator.java ---
@@ -77,10 +81,43 @@
private final CodeGenerator<T> codeGenerator;
public final JDefinedClass clazz;
- private final LinkedList<SizedJBlock>[] blocks;
+
private final JCodeModel model;
private final OptionSet optionManager;
+ private ClassGenerator<T> innerClassGenerator;
+ private LinkedList<SizedJBlock>[] blocks;
+ private LinkedList<SizedJBlock>[] oldBlocks;
+
+ /**
+ * Assumed that field has 3 indexes within the constant pull: index of
the CONSTANT_Fieldref_info +
--- End diff --
I'm not entirely sure the calculation is correct, in terms of # of entries
per field in constant pool of a class.
Per JVM spec, each class field has CONSTANT_Fieldref_info (1 entry), which
has class_index and name_and_type_index. The class_index points
CONSTANT_Class_info, which is shared by across all the class fields. The second
points to CONSTANT_NameAndType_info (1 entry), which points to name (1 entry)
and descriptor (1 entry). Therefore, for each class field, at least 4 entries
are required in constant pool. Similarly, we could get 4 entries for each
method.
Besides fields and methods, we also have to take constant literal into
account, like int, float , string ... constant. For constant literals, since we
apply source-code copy for build-in-function /udf, it's hard to figure out
exactly how many constants are used in the generated class.
Given the above reasons, I'm not sure whether it makes sense to try to come
up with a formula to estimate the maximum # of fields a generated class could
have. If the estimation is not accurate, then what if we just provides a
ballpark estimation and put some 'magic' number here?
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