Android Open Source - DKO Usage Stats

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Back to project page DKO.

License

The source code is released under:

GNU Lesser General Public License

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Java Source Code

package org.kered.dko;
//w  w w. ja va  2s .co  m
import java.lang.reflect.InvocationTargetException;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.logging.Logger;

import javax.sql.DataSource;

import org.kered.dko.persistence.QuerySize;

class UsageStats {

  private static final int SIX_MONTHS_AGO = 1000 * 60 * 60 * 24 * 265 / 2;
  private static Map<Integer, QuerySize> cache = null;
  private static long median = 0;
  private static final Logger log = Logger.getLogger("org.kered.dko.UsageStats");

  public static long estimateRowCount(final Query<? extends Table> q1) {
    if (cache == null) init();
    final int hashCode = q1.hashCode();
    QuerySize qs = cache.get(hashCode);
    if (qs==null) {
      try {
        qs = new QuerySize();
        qs.setId((long) hashCode);
        qs.setHashCode(hashCode);
        qs.setRowCount(q1.count());
        qs.setLastSeen(System.currentTimeMillis());
        final Class<? extends Table> type = q1.getType();
        try {
          qs.setSchemaName(Util.getSchemaName(type));
          qs.setTableName(Util.getTableName(type));
        } catch (final Exception e) {
          log.warning("could not get schema or table info from type: "+ type +" --- "+ e);
        }
        qs.save();
      } catch (final SQLException e) {
        log.warning("could not get count (reverting to median): "+ e);
        return (long) (median + Math.random()*10);
      }
    }
    return qs.getRowCount();
  }

  private synchronized static void init() {
    if (cache != null) return;
    try {
      //DataSource ds = (DataSource) Class.forName("org.kered.dko.persistence.Util").getMethod("getDS", null).invoke(null);
      cache = QuerySize.ALL.where(
          QuerySize.LAST_SEEN.gt(System.currentTimeMillis()
              - SIX_MONTHS_AGO)).mapBy(QuerySize.HASH_CODE);
      final List<QuerySize> values = new ArrayList<QuerySize>(cache.values());
      final int count = values.size();
      final long[] rowCounts = new long[count];
      for (int i = 0; i < count; ++i) {
        rowCounts[i] = values.get(i).getRowCount();
      }
      Arrays.sort(rowCounts);
      median = median(rowCounts);
    } catch (final SQLException e) {
      e.printStackTrace();
    }
  }

  private static long median(final long[] a) {
    if (a.length==0) return 0;
    final int m = a.length / 2;
    if (a.length%2 == 1) return a[m];
    else return (a[m-1] + a[m]) / 2;
  }

}

Java Source Code List