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https://issues.apache.org/jira/browse/PIG-2643?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13251307#comment-13251307
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Julien Le Dem commented on PIG-2643:
------------------------------------
what about this?
* call of a static method the same way a non-defined UDF can be:
{code}
a = load 'thing' as (x:long);
b = foreach a generate java.lang.Math.sqrt(x) as sqrt;
{code}
* definition of a UDF through an expression (for a strict definition of those
expressions).
{code}
c = load 'thing' as (x:bag{t:(v:chararray)});
DEFINE join com.google.common.base.Joiner.on('-').skipNulls().join;
d = foreach c generate join(x);
{code}
An expression being defined as follows:
{code}
{class}.{static method|constructor}([{primitive value}[,{primitive
value}]*])[.{method}([{primitive value}[,{primitive value}]*])]*.{method}
{code}
The exact method to use can be evaluated through reflection using the
expression and input schema.
* For methods called on the incoming objects (ex: concat) there is a finite set
of those as they are the methods available on the types supported by Pig, they
can just all be defined as builtins once and for all. That would simplify the
other cases above.
> Use bytecode generation to make a performance replacement for InvokeForLong,
> InvokeForString, etc
> -------------------------------------------------------------------------------------------------
>
> Key: PIG-2643
> URL: https://issues.apache.org/jira/browse/PIG-2643
> Project: Pig
> Issue Type: Improvement
> Reporter: Jonathan Coveney
> Assignee: Jonathan Coveney
> Priority: Minor
> Labels: codegen
> Fix For: 0.11, 0.10.1
>
> Attachments: PIG-2643-0.patch
>
>
> This is basically to cut my teeth for much more ambitious code generation
> down the line, but I think it could be performance and useful.
> the new syntax is:
> {code}a = load 'thing' as (x:chararray);
> define concat InvokerGenerator('java.lang.String','concat','String');
> define valueOf InvokerGenerator('java.lang.Integer','valueOf','String');
> define valueOfRadix
> InvokerGenerator('java.lang.Integer','valueOf','String,int');
> b = foreach a generate x, valueOf(x) as vOf;
> c = foreach b generate x, vOf, valueOfRadix(x, 16) as vOfR;
> d = foreach c generate x, vOf, vOfR, concat(concat(x, (chararray)vOf),
> (chararray)vOfR);
> dump d;
> {code}
> There are some differences between this version and Dmitriy's implementation:
> - it is no longer necessary to declare whether the method is static or not.
> This is gleaned via reflection.
> - as per the above, it is no longer necessary to make the first argument be
> the type of the object to invoke the method on. If it is not a static method,
> then the type will implicitly be the type you need. So in the case of concat,
> it would need to be passed a tuple of two inputs: one for the method to be
> called against (as it is not static), and then the 'string' that was
> specified. In the case of valueOf, because it IS static, then the 'String' is
> the only value.
> - The arguments are type sensitive. Integer means the Object Integer, whereas
> int (or long, or float, or boolean, etc) refer to the primitive. This is
> necessary to properly reflect the arguments. Values passed in WILL, however,
> be properly unboxed as necessary.
> - The return type will be reflected.
> This uses the ASM API to generate the bytecode, and then a custom classloader
> to load it in. I will add caching of the generated code based on the input
> strings, etc, but I wanted to get eyes and opinions on this. I also need to
> benchmark, but it should be native speed (excluding a little startup time to
> make the bytecode, but ASM is really fast).
> Another nice benefit is that this bypasses the need for the JDK, though it
> adds a dependency on ASM (which is a super tiny dependency).
> Patch incoming.
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