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// Portions Copyright [2016-2017] [Payara Foundation and/or its affiliates]

package com.sun.gjc.util;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.logging.Level;

/**
 * Maintains the Sql Tracing Cache used to store SQL statements used by the
 * applications. This is used by the JDBCRA monitoring to display the most
 * frequently used queries by applications.
 *
 * @author Shalini M
 */
public class FrequentSQLTraceCache extends SQLTraceCache {

    //Maximum size of the cache.
    protected long maxStoredEntries = 10000;
    
    public FrequentSQLTraceCache(String poolName, int numToReport, long timeToKeepQueries) {
        super(poolName, numToReport, timeToKeepQueries);
    }
    
    public FrequentSQLTraceCache(String poolName, int numToReport, long timeToKeepQueries, long maxStoredEntries) {
        super(poolName, numToReport, timeToKeepQueries);
        this.maxStoredEntries = maxStoredEntries;
    }

    /**
     * Request for adding a sql query in the form of SQLTrace to this cache.
     * If the query is already found
     * in the list, the number of times it is executed is incremented by one
     * along with the timestamp.
     * If the query is a new one, it is added to the list.
     * 
     * @param cacheObj
     */
    @Override
    public void checkAndUpdateCache(SQLTrace cacheObj) {
        if (cacheObj != null) {
            SQLTrace trace = cache.get(cacheObj.getQueryName());
            if (trace != null) {
                //If already found in the cache
                trace.setNumExecutions(trace.getNumExecutions() + 1);
                trace.setLastUsageTime(System.currentTimeMillis());
            } else {
                if (cache.size() < maxStoredEntries){
                    cache.put(cacheObj.getQueryName(), cacheObj);
                } else {
                    _logger.log(Level.WARNING, "Frequent SQL Trace Cache full, {0} not stored", cacheObj.getQueryName());
                }
            }
        }
    }

    /**
     * Returns the String representation of the list of traced sql queries
     * ordered by the number most frequently used, followed by the usage
     * timestamp. Only the top 'n' queries represented by the numTopQueriesToReport are
     * chosen for display.
     *
     * @return string representation of the list of sql queries sorted
     */
    public String getTopQueries() {
        purgeEntries();
        
        List sqlTraceList = new ArrayList(cache.values());
        Collections.sort(sqlTraceList, SQLTrace.SQLTraceFrequencyComparator);
        
        StringBuilder sb = new StringBuilder();
        for (SQLTrace sqlTrace : sqlTraceList) {
            sb.append(LINE_BREAK);
            sb.append(sqlTrace.getQueryName());
            sb.append(" executions: ").append(sqlTrace.getNumExecutions());
        }
        return sb.toString();
    }
}