Trino UDF Plugin: Which is the corresponding Java type to map(string,string)-CodePudding

I am creating a plugin to host an UDF, it is an http_get function, receiving the httpAddress path, the query parameters and the request headers. It is implemeted in scala:

  @ScalarFunction(value = "http_get", deterministic = true)
  @Description("Returns the result of an Http Get request")
  @SqlType(value = StandardTypes.VARCHAR)
  def httpGetFromArrayMap(
                           @SqlType(StandardTypes.VARCHAR) httpAddress: Slice,
                           @SqlType(constants.STRING_MAP) parameters: ImmutableMap[Slice, Slice],
                           @SqlNullable @SqlType(constants.STRING_MAP) headers: ImmutableMap[Slice, Slice],
                         ): String = {

    val stringHeaders = castSliceMap(headers)
    val stringParams = castSliceMap(parameters)
    val request = Http(httpAddress.toStringUtf8).headers(stringHeaders).params(stringParams)
    val stringResponse = request.asString.body
    stringResponse
  }

When running on trino, it raises the following exception:

io.trino.spi.TrinoException: Exact implementation of http_get do not match expected java types.

The problem is: What is the corresponding java type to map(varchar,varchar)?

I've tried Many:

Scala Map[String, String]
Java Map<String, String>
Java Map<Slice, Slice>
ImmutableMap<String, String>
ImmutableMap<Slice, Slice>

Can't find any example of plugin implementing a function which receives a map.

Any help is appreciated. Thanks

CodePudding user response：

Disclaimer: I'm not familiar at all with Trino UDF

According to the examples you can find in Trino repository, the type to use for a SqlType("map(X,y)") is io.trino.spi.block.Block.

The Block can then be manipulated to extract its content as if it were a regular Map.

See for instance: https://github.com/trinodb/trino/blob/master/core/trino-main/src/main/java/io/trino/operator/scalar/MathFunctions.java#L1340