Package org.apache.drill.exec.physical.resultSet.model.single

Class SingleSchemaInference

java.lang.Object

org.apache.drill.exec.physical.resultSet.model.single.SingleSchemaInference

public class SingleSchemaInference
extends Object

Produce a metadata schema from a vector container. Used when given a record batch without metadata.

At runtime, a vector container is a holder for a batch of rows. Here we are concerned with metadata where we see a vector container as implementing a tree of column schemas, expressed as the MaterializedField associated with a vector. The tree structure comes from the structured vectors such as maps, unions, lists and so on.

This class is, essentially, a tree converter: it converts a tree of vectors to a tree of metadata.

The schema is inferred recursively by walking the vector tree that defines a batches's structure. For a classic relational tuple, the tree has just a vector container and a set of primitive vectors. But, once we add array (repeated), variant (LIST, UNION) and tuple (MAP) columns, the tree grows quite complex.

Constructor Summary

Constructors

Constructor	Description
SingleSchemaInference()

Method Summary

Modifier and Type	Method	Description
TupleMetadata	infer(VectorContainer container)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

SingleSchemaInference

public SingleSchemaInference()

Method Details

infer

public TupleMetadata infer(VectorContainer container)