godfrey he created FLINK-5571:
---------------------------------
Summary: add open/close methods for UserDefinedFunction in
TableAPI & SQL
Key: FLINK-5571
URL: https://issues.apache.org/jira/browse/FLINK-5571
Project: Flink
Issue Type: New Feature
Components: Table API & SQL
Reporter: godfrey he
Assignee: godfrey he
Currently, a User Defined Function (UDF) in table API & SQL works on zero, one,
or multiple values in custom evaluation method. Many UDFs need more complex
features, e.g. report metrics, get parameters from job configuration, or get
extra data from distribute cache file, etc. Adding open and close methods in
UserDefinedFunction class can solve this problem. The code cloud look like:
{code}
trait UserDefinedFunction {
def open(context: UDFContext): Unit = {}
def close(): Unit = {}
}
{code}
UDFContext contains the information about metric reporters, job parameters,
distribute cache, etc. The code cloud look like:
{code}
class UDFContext(val context: RuntimeContext) {
def getMetricGroup: MetricGroup = ???
def getDistributedCacheFile(name: String): File = ???
def getJobParameter(key: String, default: String): String = ???
}
{code}
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