Mapping from String to List in a Dataset
I'm trying to map from String to List<String>. How should I come up with Encoder<List<String>>?
Row data = RowFactory.create("123");
StructType schema = new StructType(new StructField{
new StructField("text", DataTypes.StringType, false, Metadata.empty())
});
Dataset<Row> df = spark.createDataFrame(data, schema)
.map(s -> Arrays.<String>asList(s), ???);
I've got this far:
I've found two answers myself. In both cases, you'll be using Encoders.bean() static method. But as for the first solution, you can just pass it List.class:
Row data = RowFactory.create("123");
StructType schema = new StructType(new StructField{
new StructField("text", DataTypes.StringType, false, Metadata.empty())
});
Dataset<Row> df = spark.createDataFrame(data, schema)
.map(s -> Arrays.<String>asList(s), Encoders.bean(List.class));
In the second solution (which is more concrete but a little ugly):
Row data = RowFactory.create("123");
StructType schema = new StructType(new StructField{
new StructField("text", DataTypes.StringType, false, Metadata.empty())
});
Dataset<Row> df = spark.createDataFrame(data, schema)
.map(s -> Arrays.<String>asList(s), Encoders.bean((Class<List<String>>) Collections.<String>emptyList().getClass()));
While both these solutions compile, but both of them face a runtime error:
Exception in thread "main" java.lang.AssertionError: assertion failed
And it refers to the .map() line.
The only way I've found around the problem is this:
Row data = RowFactory.create("123");
StructType schema = new StructType(new StructField{
new StructField("text", DataTypes.StringType, false, Metadata.empty())
});
Dataset<Row> df = spark.createDataFrame(data, schema)
.map(s -> new DummyList(s), Encoders.bean(DummyList.class));
While the DummyList is:
class DummyList implements Serializable
{
public ArrayList<String> list = new ArrayList<>();
public DummyList(String s) {
list.add(s);
}
}
Of course, this is just a hack. I won't be submitting this as the answer since I hope someone can come up with a elegant solution to this problem.
java apache-spark
asked Nov 14 '18 at 3:44
MehranMehran
3,930746112
add a comment |
I'm trying to map from String to List<String>. How should I come up with Encoder<List<String>>?
Row data = RowFactory.create("123");
StructType schema = new StructType(new StructField{
new StructField("text", DataTypes.StringType, false, Metadata.empty())
});
Dataset<Row> df = spark.createDataFrame(data, schema)
.map(s -> Arrays.<String>asList(s), ???);
I've got this far:
I've found two answers myself. In both cases, you'll be using Encoders.bean() static method. But as for the first solution, you can just pass it List.class:
Row data = RowFactory.create("123");
StructType schema = new StructType(new StructField{
new StructField("text", DataTypes.StringType, false, Metadata.empty())
});
Dataset<Row> df = spark.createDataFrame(data, schema)
.map(s -> Arrays.<String>asList(s), Encoders.bean(List.class));
In the second solution (which is more concrete but a little ugly):
Row data = RowFactory.create("123");
StructType schema = new StructType(new StructField{
new StructField("text", DataTypes.StringType, false, Metadata.empty())
});
Dataset<Row> df = spark.createDataFrame(data, schema)
.map(s -> Arrays.<String>asList(s), Encoders.bean((Class<List<String>>) Collections.<String>emptyList().getClass()));
While both these solutions compile, but both of them face a runtime error:
Exception in thread "main" java.lang.AssertionError: assertion failed
And it refers to the .map() line.
The only way I've found around the problem is this:
Row data = RowFactory.create("123");
StructType schema = new StructType(new StructField{
new StructField("text", DataTypes.StringType, false, Metadata.empty())
});
Dataset<Row> df = spark.createDataFrame(data, schema)
.map(s -> new DummyList(s), Encoders.bean(DummyList.class));
While the DummyList is:
class DummyList implements Serializable
{
public ArrayList<String> list = new ArrayList<>();
public DummyList(String s) {
list.add(s);
}
}
Of course, this is just a hack. I won't be submitting this as the answer since I hope someone can come up with a elegant solution to this problem.
java apache-spark
asked Nov 14 '18 at 3:44
MehranMehran
3,930746112
add a comment |
I'm trying to map from String to List<String>. How should I come up with Encoder<List<String>>?
Row data = RowFactory.create("123");
StructType schema = new StructType(new StructField{
new StructField("text", DataTypes.StringType, false, Metadata.empty())
});
Dataset<Row> df = spark.createDataFrame(data, schema)
.map(s -> Arrays.<String>asList(s), ???);
I've got this far:
I've found two answers myself. In both cases, you'll be using Encoders.bean() static method. But as for the first solution, you can just pass it List.class:
Row data = RowFactory.create("123");
StructType schema = new StructType(new StructField{
new StructField("text", DataTypes.StringType, false, Metadata.empty())
});
Dataset<Row> df = spark.createDataFrame(data, schema)
.map(s -> Arrays.<String>asList(s), Encoders.bean(List.class));
In the second solution (which is more concrete but a little ugly):
Row data = RowFactory.create("123");
StructType schema = new StructType(new StructField{
new StructField("text", DataTypes.StringType, false, Metadata.empty())
});
Dataset<Row> df = spark.createDataFrame(data, schema)
.map(s -> Arrays.<String>asList(s), Encoders.bean((Class<List<String>>) Collections.<String>emptyList().getClass()));
While both these solutions compile, but both of them face a runtime error:
Exception in thread "main" java.lang.AssertionError: assertion failed
And it refers to the .map() line.
The only way I've found around the problem is this:
Row data = RowFactory.create("123");
StructType schema = new StructType(new StructField{
new StructField("text", DataTypes.StringType, false, Metadata.empty())
});
Dataset<Row> df = spark.createDataFrame(data, schema)
.map(s -> new DummyList(s), Encoders.bean(DummyList.class));
While the DummyList is:
class DummyList implements Serializable
{
public ArrayList<String> list = new ArrayList<>();
public DummyList(String s) {
list.add(s);
}
}
Of course, this is just a hack. I won't be submitting this as the answer since I hope someone can come up with a elegant solution to this problem.
java apache-spark
asked Nov 14 '18 at 3:44
MehranMehran
3,930746112
I'm trying to map from String to List<String>. How should I come up with Encoder<List<String>>?
Row data = RowFactory.create("123");
StructType schema = new StructType(new StructField{
new StructField("text", DataTypes.StringType, false, Metadata.empty())
});
Dataset<Row> df = spark.createDataFrame(data, schema)
.map(s -> Arrays.<String>asList(s), ???);
I've got this far:
I've found two answers myself. In both cases, you'll be using Encoders.bean() static method. But as for the first solution, you can just pass it List.class:
Row data = RowFactory.create("123");
StructType schema = new StructType(new StructField{
new StructField("text", DataTypes.StringType, false, Metadata.empty())
});
Dataset<Row> df = spark.createDataFrame(data, schema)
.map(s -> Arrays.<String>asList(s), Encoders.bean(List.class));
In the second solution (which is more concrete but a little ugly):
Row data = RowFactory.create("123");
StructType schema = new StructType(new StructField{
new StructField("text", DataTypes.StringType, false, Metadata.empty())
});
Dataset<Row> df = spark.createDataFrame(data, schema)
.map(s -> Arrays.<String>asList(s), Encoders.bean((Class<List<String>>) Collections.<String>emptyList().getClass()));
While both these solutions compile, but both of them face a runtime error:
Exception in thread "main" java.lang.AssertionError: assertion failed
And it refers to the .map() line.
The only way I've found around the problem is this:
Row data = RowFactory.create("123");
StructType schema = new StructType(new StructField{
new StructField("text", DataTypes.StringType, false, Metadata.empty())
});
Dataset<Row> df = spark.createDataFrame(data, schema)
.map(s -> new DummyList(s), Encoders.bean(DummyList.class));
While the DummyList is:
class DummyList implements Serializable
{
public ArrayList<String> list = new ArrayList<>();
public DummyList(String s) {
list.add(s);
}
}
Of course, this is just a hack. I won't be submitting this as the answer since I hope someone can come up with a elegant solution to this problem.
java apache-spark
java apache-spark
asked Nov 14 '18 at 3:44
MehranMehran
3,930746112
asked Nov 14 '18 at 3:44
MehranMehran
3,930746112
edited Nov 15 '18 at 22:19
Mehran
asked Nov 14 '18 at 3:44
MehranMehran
3,930746112
asked Nov 14 '18 at 3:44
MehranMehran
3,930746112
asked Nov 14 '18 at 3:44
MehranMehran
3,930746112
3,930746112
add a comment |
add a comment |
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