java - Unable to extract array/list from dataframe, AnalysisException : need struct type but got binary -


i have dataset string[], , struggling extract columns out of it. here's code

import static org.apache.spark.sql.functions.col;  //read parquet data dataset<row> readerdf = spark.readstream().format("parquet").  list<string> columns = arrays.aslist("city","country"); //interested in field in data 'fieldmap' map<string,string>  dataset<string[]> stringarrdf = readerdf.map((mapfunction<row, string[]>) row -> {                     map<string,string> fields = row.getjavamap(row.fieldindex("fieldmap"));     list<string> columnlist = new arraylist<>();                     columns.foreach(columnname ->     {         columnlist.add(fields.getordefault(columnname, ""));     });     return columnlist.toarray(new string[columns.size]); }, encoders.kryo(string[].class));  //i expecting extract city here: dataset ds = stringarrdf.select(col("value").getitem(1).as("city"));

but fails below exception.

exception in thread "main" org.apache.spark.sql.analysisexception: can't extract value value#22;

how can access string[] or list field dataset?

you getting below error.

exception in thread "main" org.apache.spark.sql.analysisexception: can't extract value value#22: need struct type got binary;

you using encoders.kryo(string[].class) creating stringarrdf. if check documentation encoders.kryo, says

creates encoder serializes objects of type t using kryo. encoder maps t single byte array (binary) field.

use spark.implicits().newstringarrayencoder() encoding string[].


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