Select results truncated without error message - google-cloud-sql

Question

I'm using Google Cloud SQL from an App Engine application via Java and JDBC.
I select rows of a table using following code:
public void processGcmRegistrations(String whereCondition, String appName,
String[] appVariants, boolean onlyTestDevices,
String orderByCondition,
GcmRegistrationProcessor processor) throws DbException {
if (whereCondition == null && appName == null)
throw new IllegalArgumentException("One of the parameters \"whereCondition\", " +
"\"appNmae\" must not be null.");
if (whereCondition == null) {
whereCondition = "APP_NAME = '" + appName + "' " +
createInListCondition("APP_VARIANT", appVariants);
if (onlyTestDevices)
whereCondition += " AND TEST_DEVICE = 1 ";
}
String orderByConditionStr = "";
if (orderByCondition != null)
orderByConditionStr = " ORDER BY " + orderByCondition;
String selectStmt = "SELECT GCM_ID, GCM_REGISTRATION_TIME, APP_NAME, APP_VARIANT, " +
"INSTALLATION_ID, DEVICE, LAST_UPDATE " +
"FROM GcmRegistration WHERE " + whereCondition + orderByConditionStr;
log.info("GcmIds Select: " + selectStmt);
ResultSet rs = null;
try {
long start = System.currentTimeMillis();
rs = dbConnection.createStatement().executeQuery(selectStmt);
log.info("Select duration: " + ((System.currentTimeMillis()-start)/1000) + " secs.");
int count = 0;
while (rs.next()) {
GcmRegistration reg = new GcmRegistration();
reg.gcmId = rs.getString(1);
reg.gcmRegistrationTime = rs.getLong(2);
reg.appName = rs.getString(3);
reg.appVariant = rs.getString(4);
reg.installationId = rs.getString(5);
reg.device = rs.getString(6);
reg.lastUpdate = rs.getLong(7);
processor.processGcmRegistration(reg);
count++;
}
log.info(count + " GcmRegistrations processed.");
} catch (Exception e) {
String errorMsg = "Selecting GCM_IDs from table GcmRegistration failed.";
log.log(Level.SEVERE, errorMsg, e);
throw new DbException(errorMsg, e);
} finally {
if (rs != null)
rs.close();
}
}
I always execute this method with the same parameters and receive usually about 152000 rows.
In rare cases (I guess 1 from 50) I receive only about 62000 rows without any exception! rs.next() returns false, although not all result rows are delivered.
For Google: Last time this happened was 8/22/14 23:20 (MEST)