edu.berkeley.cs186.database.query

Class QueryPlan

java.lang.Object

edu.berkeley.cs186.database.query.QueryPlan

public class QueryPlan
extends Object

QueryPlan provides a set of functions to generate simple queries. Calling the methods corresponding to SQL syntax stores the information in the QueryPlan, and calling execute generates and executes a QueryPlan DAG.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	QueryPlan.PredicateOperator

Constructor Summary

Constructors

Constructor and Description
QueryPlan(Database.Transaction transaction, String startTableName) Creates a new QueryPlan within transaction.

Method Summary

Methods

Modifier and Type	Method and Description
void	average(String column) Add an average on column.
void	count() Add a count aggregate to this query.
Iterator<Record>	execute() Generates a naïve QueryPlan in which all joins are at the bottom of the DAG followed by all where predicates, an optional group by operator, and a set of selects (in that order).
void	groupBy(String column) Set the group by column for this query.
void	join(String tableName, String leftColumnName, String rightColumnName) Join the leftColumnName column of the existing queryplan against the rightColumnName column of tableName.
void	select(List<String> columnNames) Add a select operator to the QueryPlan with a list of column names.
void	sum(String column) Add a sum on column.
void	where(String column, QueryPlan.PredicateOperator comparison, DataBox value) Add a where operator.

Methods inherited from class java.lang.Object

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

Constructor Detail

QueryPlan

public QueryPlan(Database.Transaction transaction,
         String startTableName)

Creates a new QueryPlan within transaction. The base table is startTableName.

Parameters:

transaction - the transaction containing this query

startTableName - the source table for this query

Method Detail

select

public void select(List<String> columnNames)
            throws QueryPlanException

Add a select operator to the QueryPlan with a list of column names. Can only specify one set of selections.

Parameters:

columnNames - the columns to select

Throws:

QueryPlanException

where

public void where(String column,
         QueryPlan.PredicateOperator comparison,
         DataBox value)
           throws QueryPlanException

Add a where operator. Only returns columns in which the column fulfills the predicate relative to value.

Parameters:

column - the column to specify the predicate on

comparison - the comparator

value - the value to compare against

Throws:

QueryPlanException

groupBy

public void groupBy(String column)
             throws QueryPlanException

Set the group by column for this query.

Parameters:

column - the column to group by

Throws:

QueryPlanException

count

public void count()
           throws QueryPlanException

Add a count aggregate to this query. Only can specify count(*).

Throws:

QueryPlanException

average

public void average(String column)
             throws QueryPlanException

Add an average on column. Can only average over integer or float columns.

Parameters:

column - the column to average

Throws:

QueryPlanException

sum

public void sum(String column)
         throws QueryPlanException

Add a sum on column. Can only sum integer or float columns

Parameters:

column - the column to sum

Throws:

QueryPlanException

join

public void join(String tableName,
        String leftColumnName,
        String rightColumnName)

Join the leftColumnName column of the existing queryplan against the rightColumnName column of tableName.

Parameters:

tableName - the table to join against

leftColumnName - the join column in the existing QueryPlan

rightColumnName - the join column in tableName

execute

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

Generates a naïve QueryPlan in which all joins are at the bottom of the DAG followed by all where predicates, an optional group by operator, and a set of selects (in that order).

Returns:

an iterator of records that is the result of this query

Throws:

DatabaseException

QueryPlanException