/* This file is part of VoltDB.
* Copyright (C) 2008-2017 VoltDB Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
package uniquedevices;
import java.io.IOException;
import org.voltdb.SQLStmt;
import org.voltdb.VoltProcedure;
import org.voltdb.VoltTable;
import org.voltdb_hll.HyperLogLog;
public class CountDeviceHybrid extends VoltProcedure {
public final static long MAX_EXACT_COUNT = 1000;
final static SQLStmt estimatesSelect = new SQLStmt("select devicecount, hll from estimates where appid = ?;");
final static SQLStmt estimatesUpsert = new SQLStmt("upsert into estimates (appid, devicecount, hll) values (?, ?, ?);");
final static SQLStmt exactUpsert = new SQLStmt("upsert into exact (appid, deviceid) values (?, ?);");
final static SQLStmt exactCardinality = new SQLStmt("select count(*) from exact where appid = ?;");
final static SQLStmt exactClear = new SQLStmt("delete from exact where appid = ?;");
public VoltTable[] run(long appId, long hashedDeviceId) throws IOException {
// get the HLL bytes and curret count from the db
voltQueueSQL(estimatesSelect, EXPECT_ZERO_OR_ONE_ROW, appId);
VoltTable estimatesTable = voltExecuteSQL()[0];
HyperLogLog hll = null;
long current = 0;
// if the row with the hyperloglog blob exists...
if (estimatesTable.advanceRow()) {
current = estimatesTable.getLong("devicecount");
byte[] hllBytes = estimatesTable.getVarbinary("hll");
hll = HyperLogLog.fromBytes(hllBytes);
}
// otherwise create a hyperloglog blob
else {
hll = new HyperLogLog(12);
}
// offer the hashed device id to the HLL
hll.offerHashed(hashedDeviceId);
long newEstimate = current;
// exact mode
if (current < MAX_EXACT_COUNT) {
voltQueueSQL(exactUpsert, EXPECT_ZERO_OR_ONE_ROW, appId, hashedDeviceId);
voltQueueSQL(exactCardinality, EXPECT_SCALAR_LONG, appId);
newEstimate = voltExecuteSQL()[1].asScalarLong();
// clear the exact table for this appid once it's not needed
if (newEstimate == MAX_EXACT_COUNT) {
voltQueueSQL(exactClear, EXPECT_SCALAR_MATCH(MAX_EXACT_COUNT), appId);
voltExecuteSQL();
}
}
// estimate mode
else if (hll.getDirty()) {
newEstimate = Math.max(MAX_EXACT_COUNT, hll.cardinality());
}
// if the estimates row needs updating, upsert it
if ((newEstimate != current) || hll.getDirty()) {
voltQueueSQL(estimatesUpsert, EXPECT_SCALAR_MATCH(1), appId, newEstimate, hll.toBytes());
return voltExecuteSQL(true);
}
return null;
}
}