edu.berkeley.cs186.database.query

Class GroupByOperator

java.lang.Object

edu.berkeley.cs186.database.query.QueryOperator

edu.berkeley.cs186.database.query.GroupByOperator

public class GroupByOperator
extends QueryOperator

Nested Class Summary

Nested classes/interfaces inherited from class edu.berkeley.cs186.database.query.QueryOperator

QueryOperator.OperatorType

Constructor Summary

Constructors

Constructor and Description
GroupByOperator(QueryOperator source, Database.Transaction transaction, String groupByColumn) Create a new GroupByOperator that pulls from source and groups by groupByColumn.

Method Summary

Methods

Modifier and Type	Method and Description
protected Schema	computeSchema()
Iterator<Record>	execute() Read input tuples from source, group by groupByColumn, and return an iterator.

Methods inherited from class edu.berkeley.cs186.database.query.QueryOperator

checkColumnNameEquality, checkSchemaForColumn, getDestination, getOutputSchema, getSource, getType, isGroupBy, isIndexScan, isJoin, isSelect, isSequentialScan, isWhere, setDestination, setOutputSchema, setSource

Methods inherited from class java.lang.Object

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

Constructor Detail

GroupByOperator

public GroupByOperator(QueryOperator source,
               Database.Transaction transaction,
               String groupByColumn)
                throws QueryPlanException

Create a new GroupByOperator that pulls from source and groups by groupByColumn.

Parameters:

source - the source operator of this operator

transaction - the transaction containing this operator

groupByColumn - the column to group on

Throws:

QueryPlanException

Method Detail

execute

public Iterator<Record> execute()
                         throws QueryPlanException,
                                DatabaseException

Read input tuples from source, group by groupByColumn, and return an iterator. Inserts MarkerRecord between each group.

Specified by:

execute in class QueryOperator

Returns:

Throws:

QueryPlanException

DatabaseException

computeSchema

protected Schema computeSchema()
                        throws QueryPlanException

Specified by:

computeSchema in class QueryOperator

Throws:

QueryPlanException