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Adressing many TODOs and improving documentation of the search engine.

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This commit is contained in:
Rodrigo Damazio
2012-01-06 04:38:54 -02:00
parent ff15031113
commit 96d740db64
5 changed files with 125 additions and 28 deletions
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MyTracks/src/com/google/android/apps/mytracks/content/SearchEngine.java
+108 -15
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@@ -27,21 +27,34 @@ import java.util.Comparator;
import java.util.SortedSet;
import java.util.TreeSet;
/**
* Engine for searching for tracks and waypoints by text.
*
* @author Rodrigo Damazio
*/
public class SearchEngine {
/** How much we promote a match in the track category. */
private static final double TRACK_CATEGORY_PROMOTION = 2.0;
/** How much we promote a match in the track description. */
private static final double TRACK_DESCRIPTION_PROMOTION = 8.0;
/** How much we promote a match in the track name. */
private static final double TRACK_NAME_PROMOTION = 16.0;
/** How much we promote a waypoint result if it's in the currently-selected track. */
private static final double CURRENT_TRACK_WAYPOINT_PROMOTION = 2.0;
/** How much we promote a track result if it's the currently-selected track. */
private static final double CURRENT_TRACK_DEMOTION = 0.5;
/** Maximum number of waypoints which will be retrieved and scored. */
private static final int MAX_SCORED_WAYPOINTS = 100;
/**
* Description of a search query, along with all contextual data needed to execute it.
*/
public static class SearchQuery {
public SearchQuery(String textQuery, Location currentLocation, long currentTrackId,
long currentTimestamp) {
@@ -51,12 +64,15 @@ public class SearchEngine {
this.currentTimestamp = currentTimestamp;
}
final String textQuery;
final Location currentLocation;
final long currentTrackId;
final long currentTimestamp;
public final String textQuery;
public final Location currentLocation;
public final long currentTrackId;
public final long currentTimestamp;
}
/**
* Description of a search result which has been retrieved and scored.
*/
public static class ScoredResult {
ScoredResult(Track track, double score) {
this.track = track;
@@ -70,11 +86,12 @@ public class SearchEngine {
this.score = score;
}
final Track track;
final Waypoint waypoint;
final double score;
public final Track track;
public final Waypoint waypoint;
public final double score;
}
/** Comparador for scored results. */
private static final Comparator<ScoredResult> SCORED_RESULT_COMPARATOR =
new Comparator<ScoredResult>() {
@Override
@@ -88,7 +105,8 @@ public class SearchEngine {
// Arbitrary ordering, by ID.
long id1 = r1.track != null ? r1.track.getId() : r1.waypoint.getId();
long id2 = r2.track != null ? r2.track.getId() : r2.waypoint.getId();
return (int) (id2 - id1);
long diff = id2 - id1;
return Long.signum(diff);
}
};
@@ -98,6 +116,12 @@ public class SearchEngine {
providerUtils = MyTracksProviderUtils.Factory.get(ctx);
}
/**
* Executes a search query and returns a set of sorted results.
*
* @param query the query to execute
* @return a set of results, sorted according to their score
*/
public SortedSet<ScoredResult> doSearch(SearchQuery query) {
ArrayList<Track> tracks = new ArrayList<Track>();
ArrayList<Waypoint> waypoints = new ArrayList<Waypoint>();
@@ -112,20 +136,25 @@ public class SearchEngine {
return scoredResults;
}
/**
* Retrieves tracks matching the given query from the database.
*
* @param query the query to retrieve for
* @param tracks list to fill with the resulting tracks
*/
private void retrieveTracks(SearchQuery query, ArrayList<Track> tracks) {
// TODO: Use a different sort order as a ranking function.
String queryLikeSelection = "%" + query.textQuery + "%";
String trackSelection =
TracksColumns.NAME + " LIKE ? OR " +
TracksColumns.DESCRIPTION + " LIKE ? OR " +
TracksColumns.CATEGORY + " LIKE ?";
String order = TracksColumns._ID + " DESC LIMIT 1000"; // Favor recent tracks.
String[] trackSelectionArgs = new String[] {
queryLikeSelection,
queryLikeSelection,
queryLikeSelection };
// TODO: Limit number of results to be scored.
Cursor tracksCursor = providerUtils.getTracksCursor(trackSelection, trackSelectionArgs);
Cursor tracksCursor = providerUtils.getTracksCursor(trackSelection, trackSelectionArgs, order);
if (tracksCursor != null) {
try {
tracks.ensureCapacity(tracksCursor.getCount());
@@ -139,18 +168,25 @@ public class SearchEngine {
}
}
/**
* Retrieves waypoints matching the given query from the database.
*
* @param query the query to retrieve for
* @param tracks list to fill with the resulting waypoints
*/
private void retrieveWaypoints(SearchQuery query, ArrayList<Waypoint> waypoints) {
// TODO: Use a different sort order as a ranking function.
String queryLikeSelection2 = "%" + query.textQuery + "%";
String waypointSelection =
WaypointsColumns.NAME + " LIKE ? OR " +
WaypointsColumns.DESCRIPTION + " LIKE ? OR " +
WaypointsColumns.CATEGORY + " LIKE ?";
String order = WaypointsColumns._ID + " DESC"; // Favor recent waypoints.
String[] waypointSelectionArgs = new String[] {
queryLikeSelection2,
queryLikeSelection2,
queryLikeSelection2 };
Cursor waypointsCursor = providerUtils.getWaypointsCursor(waypointSelection, waypointSelectionArgs, MAX_SCORED_WAYPOINTS);
Cursor waypointsCursor = providerUtils.getWaypointsCursor(waypointSelection, waypointSelectionArgs, order,
MAX_SCORED_WAYPOINTS);
if (waypointsCursor != null) {
try {
waypoints.ensureCapacity(waypointsCursor.getCount());
@@ -164,6 +200,13 @@ public class SearchEngine {
}
}
/**
* Scores a collection of track results.
*
* @param tracks the results to score
* @param query the query to score for
* @param output the collection to fill with scored results
*/
private void scoreTrackResults(Collection<Track> tracks, SearchQuery query, Collection<ScoredResult> output) {
for (Track track : tracks) {
// Calculate the score.
@@ -174,12 +217,20 @@ public class SearchEngine {
}
}
/**
* Scores a single track result.
*
* @param query the query to score for
* @param track the results to score
* @return the score for the track
*/
private double scoreTrackResult(SearchQuery query, Track track) {
double score = 1.0;
score *= getTitleBoost(query, track.getName(), track.getDescription(), track.getCategory());
TripStatistics statistics = track.getStatistics();
// TODO: Also boost for proximity to the currently-centered position on the map.
double meanLatitude = (statistics.getTop() + statistics.getBottom()) / 2000000.0;
double meanLongitude = (statistics.getRight() + statistics.getLeft()) / 2000000.0;
score *= getDistanceBoost(query, meanLatitude, meanLongitude);
@@ -195,6 +246,13 @@ public class SearchEngine {
return score;
}
/**
* Scores a collection of waypoint results.
*
* @param waypoints the results to score
* @param query the query to score for
* @param output the collection to fill with scored results
*/
private void scoreWaypointResults(Collection<Waypoint> waypoints, SearchQuery query, Collection<ScoredResult> output) {
for (Waypoint waypoint : waypoints) {
// Calculate the score.
@@ -205,11 +263,19 @@ public class SearchEngine {
}
}
/**
* Scores a single waypoint result.
*
* @param query the query to score for
* @param waypoint the results to score
* @return the score for the waypoint
*/
private double scoreWaypointResult(SearchQuery query, Waypoint waypoint) {
double score = 1.0;
Location location = waypoint.getLocation();
score *= getTitleBoost(query, waypoint.getName(), waypoint.getDescription(), waypoint.getCategory());
// TODO: Also boost for proximity to the currently-centered position on the map.
score *= getDistanceBoost(query, location.getLatitude(), location.getLongitude());
score *= getTimeBoost(query, location.getTime());
@@ -221,6 +287,15 @@ public class SearchEngine {
return score;
}
/**
* Calculates the boosting of the score due to the field(s) in which the match occured.
*
* @param query the query to boost for
* @param name the name of the track or waypoint
* @param description the description of the track or waypoint
* @param category the category of the track or waypoint
* @return the total boost to be applied to the result
*/
private double getTitleBoost(SearchQuery query,
String name, String description, String category) {
// Title boost: track name > description > category.
@@ -237,6 +312,13 @@ public class SearchEngine {
return boost;
}
/**
* Calculates the boosting of the score due to the recency of the matched entity.
*
* @param query the query to boost for
* @param timestamp the timestamp to calculate the boost for
* @return the total boost to be applied to the result
*/
private double getTimeBoost(SearchQuery query, long timestamp) {
// Score recent tracks higher.
long timeAgoHours = (query.currentTimestamp - timestamp) / (60L * 60L);
@@ -248,6 +330,14 @@ public class SearchEngine {
}
}
/**
* Calculates the boosting of the score due to proximity to a location.
*
* @param query the query to boost for
* @param latitude the latitude to calculate the boost for
* @param longitude the longitude to calculate the boost for
* @return the total boost to be applied to the result
*/
private double getDistanceBoost(SearchQuery query, double latitude, double longitude) {
if (query.currentLocation == null) {
return 1.0;
@@ -271,7 +361,10 @@ public class SearchEngine {
}
}
private static double squash(double timeAgoHours) {
return 1.0 / Math.log1p(timeAgoHours);
/**
* Squashes a number by calculating 1 / log (1 + x).
*/
private static double squash(double x) {
return 1.0 / Math.log1p(x);
}
}