com.couchbase.lite

Interface Query

All Known Implementing Classes:

From, GroupBy, Having, Joins, Limit, OrderBy, Select, Where

public interface Query

A database query used for querying data from the database. The query statement of the Query object can be fluently constructed by calling the static select methods.

Method Summary

Modifier and Type	Method and Description
ListenerToken	addChangeListener(Executor executor, QueryChangeListener listener) Adds a change listener for the changes that occur in the query results with an executor on which the changes will be posted to the listener.
ListenerToken	addChangeListener(QueryChangeListener listener) Adds a change listener for the changes that occur in the query results.
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.
void	removeChangeListener(ListenerToken token) Removes a change listener wih the given listener token.
void	setParameters(Parameters parameters) Set parameters should copy the given parameters.

Method Detail

getParameters

@Nullable
Parameters getParameters()

Returns a copies of the current parameters.

setParameters

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.

execute

@NonNull
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.

Returns:

the ResultSet for the query result.

Throws:

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

explain

@NonNull
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.

Returns:

a string describing the implementation of the compiled query.

Throws:

CouchbaseLiteException - if an error occurs

addChangeListener

@NonNull
ListenerToken addChangeListener(@NonNull
                                         QueryChangeListener listener)

Adds a change listener for the changes that occur in the query results. The changes will be delivered on the UI thread for the Android platform and on an arbitrary thread for the Java platform. When developing a Java Desktop application using Swing or JavaFX that needs to update the UI after receiving the changes, make sure to schedule the UI update on the UI thread by using SwingUtilities.invokeLater(Runnable) or Platform.runLater(Runnable) respectively.

Parameters:

listener - The listener to post changes.

Returns:

An opaque listener token object for removing the listener.

addChangeListener

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

Adds a change listener for the changes that occur in the query results with an executor on which the changes will be posted to the listener. If the executor is not specified, the changes will be delivered on the UI thread for the Android platform and on an arbitrary thread for the Java platform.

Parameters:

executor - The executor object that calls listener

listener - The listener to post changes.

Returns:

An opaque listener token object for removing the listener.

removeChangeListener

void removeChangeListener(@NonNull
                          ListenerToken token)

Removes a change listener wih the given listener token.

Parameters:

token - The listener token.