org.apache.drill.metastore.operate

Interface Read<T>

Type Parameters:

T - component unit type

All Known Implementing Classes:

AbstractRead, IcebergRead, RdbmsRead

public interface Read<T>

Drill Metastore Read interface contains methods to be implemented in order to provide read functionality from the Metastore component.

Method Summary

Modifier and Type	Method and Description
Read<T>	columns(List<MetastoreColumn> columns) Provides list of columns to be read from Metastore component.
default Read<T>	columns(MetastoreColumn... columns)
List<T>	execute() Executes read operation from Metastore component, returns obtained result in a form of list of component units which later can be transformed into suitable format.
Read<T>	filter(FilterExpression filter) Provides filter expression by which metastore component data will be filtered.
default Read<T>	metadataType(MetadataType... metadataType)
Read<T>	metadataTypes(Set<MetadataType> metadataTypes) Provides set of metadata types to be read.

Method Detail

metadataTypes

Read<T> metadataTypes(Set<MetadataType> metadataTypes)

Provides set of metadata types to be read. Note: providing at least one metadata type is required. If all metadata types should be read, MetadataType.ALL can be passed.

Parameters:

metadataTypes - set of metadata types

Returns:

current instance of Read interface implementation

metadataType

default Read<T> metadataType(MetadataType... metadataType)

filter

Read<T> filter(FilterExpression filter)

Provides filter expression by which metastore component data will be filtered. If filter expression is not indicated, all Metastore component data will be read.

Parameters:

filter - filter expression

Returns:

current instance of Read interface implementation

columns

Read<T> columns(List<MetastoreColumn> columns)

Provides list of columns to be read from Metastore component. If no columns are indicated, all columns will be read. Depending on Metastore component implementation, providing list of columns to be read, can improve retrieval performance.

Parameters:

columns - list of columns to be read from Metastore component

Returns:

current instance of Read interface implementation

columns

default Read<T> columns(MetastoreColumn... columns)

execute

List<T> execute()

Executes read operation from Metastore component, returns obtained result in a form of list of component units which later can be transformed into suitable format.

Returns:

list of component units