将UDF函数插件到Presto中的步骤是什么？

Question

我遵循了本教程并利用这个github项目编写了一个简单的'mysum'UDF函数。

@ScalarFunction("mysum")
@Description("Returns summation of two numbers")
@SqlType(StandardTypes.BIGINT)
public static long sum(@SqlType(StandardTypes.BIGINT) long num1, @SqlType(StandardTypes.BIGINT) long num2)
{
    return num1 + num2;
}

我按照下面的步骤插入UDF，但Presto未能导入该函数。由于关于编写和插入UDF的文档很少，因此非常感谢任何帮助。提前道谢。

1. 运行mvn compile和mvn package
2. 将.jar文件复制到presto（解压缩）目录/users/nithin/presto-server-0.166/plugin/udfs/
下的plugins文件夹中
3. 在Presto CLI中使用bin/launcher run运行select mysum（10,100)启动协调器，但抛出错误

下面是当我尝试在Presto cli中运行我的UDF（“mysum”）时的错误日志。很明显，Presto找不到UDF，所以插入没有成功。怎么解决？我错过了什么步骤吗？

➜  Workspaces ./presto.jar --server localhost:8080 --catalog mysql --schema default --debug
presto:default> select mysum(99,100);
Query 20170228_183509_00002_vr5dt failed: line 1:8: Function mysum not registered
com.facebook.presto.sql.analyzer.SemanticException: line 1:8: Function mysum not registered
    at com.facebook.presto.sql.analyzer.ExpressionAnalyzer$Visitor.visitFunctionCall(ExpressionAnalyzer.java:824)
    at com.facebook.presto.sql.analyzer.ExpressionAnalyzer$Visitor.visitFunctionCall(ExpressionAnalyzer.java:255)
    at com.facebook.presto.sql.tree.FunctionCall.accept(FunctionCall.java:111)
    at com.facebook.presto.sql.tree.StackableAstVisitor.process(StackableAstVisitor.java:26)
    at com.facebook.presto.sql.analyzer.ExpressionAnalyzer$Visitor.process(ExpressionAnalyzer.java:274)
    at com.facebook.presto.sql.analyzer.ExpressionAnalyzer.analyze(ExpressionAnalyzer.java:231)
    at com.facebook.presto.sql.analyzer.ExpressionAnalyzer.analyzeExpression(ExpressionAnalyzer.java:1406)
    at com.facebook.presto.sql.analyzer.StatementAnalyzer.analyzeExpression(StatementAnalyzer.java:1802)
    at com.facebook.presto.sql.analyzer.StatementAnalyzer.analyzeSelect(StatementAnalyzer.java:1623)
    at com.facebook.presto.sql.analyzer.StatementAnalyzer.visitQuerySpecification(StatementAnalyzer.java:800)
    at com.facebook.presto.sql.analyzer.StatementAnalyzer.visitQuerySpecification(StatementAnalyzer.java:188)
    at com.facebook.presto.sql.tree.QuerySpecification.accept(QuerySpecification.java:127)
    at com.facebook.presto.sql.tree.AstVisitor.process(AstVisitor.java:27)
    at com.facebook.presto.sql.analyzer.StatementAnalyzer.visitQuery(StatementAnalyzer.java:550)
    at com.facebook.presto.sql.analyzer.StatementAnalyzer.visitQuery(StatementAnalyzer.java:188)
    at com.facebook.presto.sql.tree.Query.accept(Query.java:94)
    at com.facebook.presto.sql.tree.AstVisitor.process(AstVisitor.java:27)
    at com.facebook.presto.sql.analyzer.Analyzer.analyze(Analyzer.java:68)
    at com.facebook.presto.sql.analyzer.Analyzer.analyze(Analyzer.java:60)
    at com.facebook.presto.execution.SqlQueryExecution.doAnalyzeQuery(SqlQueryExecution.java:290)
    at com.facebook.presto.execution.SqlQueryExecution.analyzeQuery(SqlQueryExecution.java:276)
    at com.facebook.presto.execution.SqlQueryExecution.start(SqlQueryExecution.java:234)
    at com.facebook.presto.execution.QueuedExecution.lambda$start$1(QueuedExecution.java:63)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
select mysum(99,100)

Answer 1

连接器插件应该提供UDF类的列表。请参阅插件#GetFunctions

default Set<Class<?>> getFunctions()
{
    return emptySet();
}

请重写方法并公开UDF类的类。