com.couchbase.lite

Class GroupBy

java.lang.Object

com.couchbase.lite.GroupBy

All Implemented Interfaces:

Query

public final class GroupBy
extends Object

A GroupBy represents the GROUP BY clause to group the query result. The GROUP BY clause is normally used with aggregate functions (AVG, COUNT, MAX, MIN, SUM) to aggregate the group of the values.

Method Summary

Modifier and Type	Method and Description
ListenerToken	addChangeListener(Executor executor, QueryChangeListener listener) Adds a query change listener with the dispatch queue on which changes will be posted.
ListenerToken	addChangeListener(QueryChangeListener listener) Adds a query change listener.
ResultSet	execute() Executes the query.
String	explain() Returns a string describing the implementation of the compiled query.
Parameters	getParameters() Returns a copies of the current parameters.
Having	having(Expression expression) Creates and chain a Having object for filtering the aggregated values from the the GROUP BY clause.
Limit	limit(Expression limit) Creates and chains a Limit object to limit the number query results.
Limit	limit(Expression limit, Expression offset) Creates and chains a Limit object to skip the returned results for the given offset position and to limit the number of results to not more than the given limit value.
OrderBy	orderBy(Ordering... orderings) Create and chain an ORDER BY component for specifying the ORDER BY clause of the query.
void	removeChangeListener(ListenerToken token) Removes a change listener wih the given listener token.
void	setParameters(Parameters parameters) Set parameters should copy the given parameters.
String	toString()

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Detail

having

@NonNull
public Having having(@NonNull
                              Expression expression)

Creates and chain a Having object for filtering the aggregated values from the the GROUP BY clause.

Parameters:

expression - The expression

Returns:

The Having object that represents the HAVING clause of the query.

orderBy

@NonNull
public OrderBy orderBy(@NonNull
                                Ordering... orderings)

Create and chain an ORDER BY component for specifying the ORDER BY clause of the query.

Parameters:

orderings - an array of the ORDER BY expressions.

Returns:

the ORDER BY component.

limit

@NonNull
public Limit limit(@NonNull
                            Expression limit)

Creates and chains a Limit object to limit the number query results.

Parameters:

limit - The limit expression.

Returns:

The Limit object that represents the LIMIT clause of the query.

limit

@NonNull
public Limit limit(@NonNull
                            Expression limit,
                            @Nullable
                            Expression offset)

Creates and chains a Limit object to skip the returned results for the given offset position and to limit the number of results to not more than the given limit value.

Parameters:

limit - The limit expression.

offset - The offset expression.

Returns:

The Limit object that represents the LIMIT clause of the query.

getParameters

public Parameters getParameters()

Returns a copies of the current parameters.

Specified by:

getParameters in interface Query

setParameters

public void setParameters(Parameters parameters)

Set parameters should copy the given parameters. Set a new parameter will also re-execute the query if there is at least one listener listening for changes.

Specified by:

setParameters in interface Query

execute

@NonNull
public ResultSet execute()
                           throws CouchbaseLiteException

Executes the query. The returning a result set that enumerates result rows one at a time. You can run the query any number of times, and you can even have multiple ResultSet active at once.

The results come from a snapshot of the database taken at the moment the run() method is called, so they will not reflect any changes made to the database afterwards.

Specified by:

execute in interface Query

Returns:

the ResultSet for the query result.

Throws:

CouchbaseLiteException - if there is an error when running the query.

explain

@NonNull
public String explain()
                        throws CouchbaseLiteException

Returns a string describing the implementation of the compiled query. This is intended to be read by a developer for purposes of optimizing the query, especially to add database indexes. It's not machine-readable and its format may change. As currently implemented, the result is two or more lines separated by newline characters: * The first line is the SQLite SELECT statement. * The subsequent lines are the output of SQLite's "EXPLAIN QUERY PLAN" command applied to that statement; for help interpreting this, see https://www.sqlite.org/eqp.html . The most important thing to know is that if you see "SCAN TABLE", it means that SQLite is doing a slow linear scan of the documents instead of using an index.

Specified by:

explain in interface Query

Returns:

a string describing the implementation of the compiled query.

Throws:

CouchbaseLiteException - if an error occurs

addChangeListener

@NonNull
public ListenerToken addChangeListener(@NonNull
                                                QueryChangeListener listener)

Adds a query change listener. Changes will be posted on the main queue.

Specified by:

addChangeListener in interface Query

Parameters:

listener - The listener to post changes.

Returns:

An opaque listener token object for removing the listener.

addChangeListener

@NonNull
public ListenerToken addChangeListener(Executor executor,
                                                @NonNull
                                                QueryChangeListener listener)

Adds a query change listener with the dispatch queue on which changes will be posted. If the dispatch queue is not specified, the changes will be posted on the main queue.

Specified by:

addChangeListener in interface Query

Parameters:

executor - The executor object that calls listener. If null, use default executor.

listener - The listener to post changes.

Returns:

An opaque listener token object for removing the listener.

removeChangeListener

public void removeChangeListener(@NonNull
                                 ListenerToken token)

Removes a change listener wih the given listener token.

Specified by:

removeChangeListener in interface Query

Parameters:

token - The listener token.

toString

@NonNull
public String toString()

Overrides:

toString in class Object