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Commit f78a4f03 authored by Marco Nelissen's avatar Marco Nelissen Committed by elektroschmock
Browse files

Improve scan time for some cases 

When the path being matched has a sqlite wildcard character in it, a "like"
match will be quite slow. Unfortunately this is fairly common, since "_"
is a wildcard character. However, because in most cases the case of the path
in the database will match the case on disk, an "=" match will work, so it
is worthwhile to try an "=" match first, before trying a "like".

If there are no wildcard characters, the "like" will be as fast as the "=",
because of the case-insensitive index on the _data column, so there is no
need to try "=" first in that case.

b/6751354

Change-Id: I1cd4efbd56a37886cb44a86acb73eb9a3c9f303d
parent dcf4128e

media/java/android/media/MediaScanner.java

+29 −11
Original line number Diff line number Diff line
@@ -1447,24 +1447,42 @@ public class MediaScanner 
    }



    FileEntry makeEntryFor(String path) {

        String key = path;

        String where;

        String[] selectionArgs;

        if (mCaseInsensitivePaths) {

            // the 'like' makes it use the index, the 'lower()' makes it correct

            // when the path contains sqlite wildcard characters

            where = "_data LIKE ?1 AND lower(_data)=lower(?1)";



        Cursor c = null;

        try {

            boolean hasWildCards = path.contains("_") || path.contains("%");



            if (hasWildCards || !mCaseInsensitivePaths) {

                // if there are wildcard characters in the path, the "like" match

                // will be slow, and it's worth trying an "=" comparison

                // first, since in most cases the case will match.

                // Also, we shouldn't do a "like" match on case-sensitive filesystems

                where = Files.FileColumns.DATA + "=?";

                selectionArgs = new String[] { path };

            } else {

            where = Files.FileColumns.DATA + "=?";

                // if there are no wildcard characters in the path, then the "like"

                // match will be just as fast as the "=" case, because of the index

                where = "_data LIKE ?1 AND lower(_data)=lower(?1)";

                selectionArgs = new String[] { path };

            }



        Cursor c = null;

        try {

            c = mMediaProvider.query(mFilesUri, FILES_PRESCAN_PROJECTION,

                    where, selectionArgs, null, null);

            if (c.moveToNext()) {

            if (!c.moveToFirst() && hasWildCards && mCaseInsensitivePaths) {

                // Try again with case-insensitive match. This will be slower, especially

                // if the path contains wildcard characters.

                // The 'like' makes it use the index, the 'lower()' makes it correct

                // when the path contains sqlite wildcard characters,

                where = "_data LIKE ?1 AND lower(_data)=lower(?1)";

                selectionArgs = new String[] { path };

                c.close();

                c = mMediaProvider.query(mFilesUri, FILES_PRESCAN_PROJECTION,

                        where, selectionArgs, null, null);

                // TODO update the path in the db with the correct case so the fast

                // path works next time?

            }

            if (c.moveToFirst()) {

                long rowId = c.getLong(FILES_PRESCAN_ID_COLUMN_INDEX);

                int format = c.getInt(FILES_PRESCAN_FORMAT_COLUMN_INDEX);

                long lastModified = c.getLong(FILES_PRESCAN_DATE_MODIFIED_COLUMN_INDEX);