Package org.apache.drill.metastore.operate

Class AbstractRead<T>

java.lang.Object

org.apache.drill.metastore.operate.AbstractRead<T>

Type Parameters:

T - Metastore metadata unit

All Implemented Interfaces:

Read<T>

Direct Known Subclasses:

IcebergRead, MongoRead, RdbmsRead

public abstract class AbstractRead<T>
extends Object
implements Read<T>

Abstract implementation of Read<T> interface which contains all boilerplace code for collecting metadata types, columns and filter condition. Given metadata types are also validated during execution.

Field Summary

Fields

Modifier and Type	Field	Description
protected final List<MetastoreColumn>	columns
protected FilterExpression	filter
protected final Set<MetadataType>	metadataTypes

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	AbstractRead(MetadataTypeValidator metadataTypeValidator)

Method Summary

Modifier and Type	Method	Description
Read<T>	columns(List<MetastoreColumn> columns)	Provides list of columns to be read from Metastore component.
final 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.
protected abstract List<T>	internalExecute()
Read<T>	metadataTypes(Set<MetadataType> metadataTypes)	Provides set of metadata types to be read.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.drill.metastore.operate.Read

columns, metadataType

Field Details

metadataTypes

protected final Set<MetadataType> metadataTypes

columns

protected final List<MetastoreColumn> columns

filter

protected FilterExpression filter

Constructor Details

AbstractRead

protected AbstractRead(MetadataTypeValidator metadataTypeValidator)

Method Details

metadataTypes

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

Description copied from interface: Read

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.

Specified by:

metadataTypes in interface Read<T>

Parameters:

metadataTypes - set of metadata types

Returns:

current instance of Read interface implementation

filter

public Read<T> filter(FilterExpression filter)

Description copied from interface: Read

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

Specified by:

filter in interface Read<T>

Parameters:

filter - filter expression

Returns:

current instance of Read interface implementation

columns

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

Description copied from interface: Read

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.

Specified by:

columns in interface Read<T>

Parameters:

columns - list of columns to be read from Metastore component

Returns:

current instance of Read interface implementation

execute

public final List<T> execute()

Description copied from interface: Read

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.

Specified by:

execute in interface Read<T>

Returns:

list of component units

internalExecute

protected abstract List<T> internalExecute()