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Bug 762978 - Make AndroidBrowserRepositorySession.recordToGuid map from hashes of record strings to record guids to reduce memory pressure. r=liuche

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This commit is contained in:
Nick Alexander 2012-06-18 11:09:43 -07:00
parent 12a235f1cf
commit 594e9875e3
1 changed files with 84 additions and 10 deletions
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94
mobile/android/base/sync/repositories/android/AndroidBrowserRepositorySession.java
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@ -57,7 +57,21 @@ public abstract class AndroidBrowserRepositorySession extends StoreTrackingRepos
public static final String LOG_TAG = "BrowserRepoSession";
protected AndroidBrowserRepositoryDataAccessor dbHelper;
private HashMap<String, String> recordToGuid;
/**
* In order to reconcile the "same record" with two *different* GUIDs (for
* example, the same bookmark created by two different clients), we maintain a
* mapping for each local record from a "record string" to
* "local record GUID".
* <p>
* The "record string" above is a "record identifying unique key" produced by
* <code>buildRecordString</code>.
* <p>
* Since we hash each "record string", this map may produce a false positive.
* In this case, we search the database for a matching record explicitly using
* <code>findByRecordString</code>.
*/
protected HashMap<Integer, String> recordToGuid;
public AndroidBrowserRepositorySession(Repository repository) {
super(repository);
@ -156,6 +170,13 @@ public abstract class AndroidBrowserRepositorySession extends StoreTrackingRepos
super.finish(delegate);
}
/**
* Produce a "record string" (record identifying unique key).
*
* @param record
* the <code>Record</code> to identify.
* @return a <code>String</code> instance.
*/
protected abstract String buildRecordString(Record record);
protected void checkDatabase() throws ProfileDatabaseException, NullCursorException {
@ -626,26 +647,40 @@ public abstract class AndroidBrowserRepositorySession extends StoreTrackingRepos
}
Logger.debug(LOG_TAG, "Searching with record string " + recordString);
String guid = getRecordToGuidMap().get(recordString);
String guid = getGuidForString(recordString);
if (guid == null) {
Logger.debug(LOG_TAG, "findExistingRecord failed to find one for " + record.guid);
return null;
}
Logger.debug(LOG_TAG, "Found one. Returning computed record.");
return retrieveByGUIDDuringStore(guid);
// Our map contained a match, but it could be a false positive. Since
// computed record string is supposed to be a unique key, we can easily
// verify our positive.
Logger.debug(LOG_TAG, "Found one. Checking stored record.");
Record stored = retrieveByGUIDDuringStore(guid);
String storedRecordString = buildRecordString(record);
if (recordString.equals(storedRecordString)) {
Logger.debug(LOG_TAG, "Existing record matches incoming record. Returning existing record.");
return stored;
}
// Oh no, we got a false positive! (This should be *very* rare --
// essentially, we got a hash collision.) Search the DB for this record
// explicitly by hand.
Logger.debug(LOG_TAG, "Existing record does not match incoming record. Trying to find record by record string.");
return findByRecordString(recordString);
}
public HashMap<String, String> getRecordToGuidMap() throws NoGuidForIdException, NullCursorException, ParentNotFoundException {
protected String getGuidForString(String recordString) throws NoGuidForIdException, NullCursorException, ParentNotFoundException {
if (recordToGuid == null) {
createRecordToGuidMap();
}
return recordToGuid;
return recordToGuid.get(new Integer(recordString.hashCode()));
}
private void createRecordToGuidMap() throws NoGuidForIdException, NullCursorException, ParentNotFoundException {
protected void createRecordToGuidMap() throws NoGuidForIdException, NullCursorException, ParentNotFoundException {
Logger.info(LOG_TAG, "BEGIN: creating record -> GUID map.");
recordToGuid = new HashMap<String, String>();
recordToGuid = new HashMap<Integer, String>();
// TODO: we should be able to do this entire thing with string concatenations within SQL.
// Also consider whether it's better to fetch and process every record in the DB into
@ -660,7 +695,7 @@ public abstract class AndroidBrowserRepositorySession extends StoreTrackingRepos
if (record != null) {
final String recordString = buildRecordString(record);
if (recordString != null) {
recordToGuid.put(recordString, record.guid);
recordToGuid.put(new Integer(recordString.hashCode()), record.guid);
}
}
cur.moveToNext();
@ -671,6 +706,45 @@ public abstract class AndroidBrowserRepositorySession extends StoreTrackingRepos
Logger.info(LOG_TAG, "END: creating record -> GUID map.");
}
/**
* Search the local database for a record with the same "record string".
* <p>
* We expect to do this only in the unlikely event of a hash
* collision, so we iterate the database completely. Since we want
* to include information about the parents of bookmarks, it is
* difficult to do better purely using the
* <code>ContentProvider</code> interface.
*
* @param recordString
* the "record string" to search for; must be n
* @return a <code>Record</code> with the same "record string", or
* <code>null</code> if none is present.
* @throws ParentNotFoundException
* @throws NullCursorException
* @throws NoGuidForIdException
*/
protected Record findByRecordString(String recordString) throws NoGuidForIdException, NullCursorException, ParentNotFoundException {
Cursor cur = dbHelper.fetchAll();
try {
if (!cur.moveToFirst()) {
return null;
}
while (!cur.isAfterLast()) {
Record record = retrieveDuringStore(cur);
if (record != null) {
final String storedRecordString = buildRecordString(record);
if (recordString.equals(storedRecordString)) {
return record;
}
}
cur.moveToNext();
}
return null;
} finally {
cur.close();
}
}
public void putRecordToGuidMap(String recordString, String guid) throws NoGuidForIdException, NullCursorException, ParentNotFoundException {
if (recordString == null) {
return;
@ -679,7 +753,7 @@ public abstract class AndroidBrowserRepositorySession extends StoreTrackingRepos
if (recordToGuid == null) {
createRecordToGuidMap();
}
recordToGuid.put(recordString, guid);
recordToGuid.put(new Integer(recordString.hashCode()), guid);
}
protected abstract Record prepareRecord(Record record);