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HBase, mail # user - Scanning a row for certain md5hash does not work


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Scanning a row for certain md5hash does not work
Paul van Hoven 2013-02-19, 18:46
I'm currently reading a book about hbase (hbase in action by manning).
In this book it is explained how to perform a scan if the rowkey is
made out of a md5 hash (page 45 in the book). My rowkey design (and
table filling method) looks like this:

SimpleDateFormat dateFormatter = new SimpleDateFormat("yyyy-MM-dd");
SimpleDateFormat timeFormatter = new SimpleDateFormat("HH:mm:ss");
Date date = dateFormatter.parse("2013-01-01");

for( int i = 0; i < 31; ++i ) {
for( int k = 0; k < 24; ++k ) {
for( int j = 0; j < 1; ++j ) {
                        //md5() is a custom method that transforms a
string into a md5 hash
byte[] ts = md5( dateFormatter.format(date) );
byte[] tm = md5( timeFormatter.format(date) );
byte[] ip = md5( generateRandomIPAddress() /* toy method that
generates ip addresses */ );
byte[] rowkey = new byte[ ts.length + tm.length + ip.length ];
System.arraycopy( ts, 0, rowkey, 0, ts.length );
System.arraycopy( tm, 0, rowkey, ts.length, tm.length );
System.arraycopy( ip, 0, rowkey, ts.length+tm.length, ip.length );
Put p = new Put( rowkey );

p.add( Bytes.toBytes("CF"), Bytes.toBytes("SampleCol"),
Bytes.toBytes( "Value_" + (i+1) + " = " + dateFormatter.format(date) +
" " + timeFormatter.format(date) ) );
toyDataTable.put( p );
}

                //custom method that adds an hour to the current date object
date = addHours( date, 1 );
}

}

Now I'd like to do the following scan (I more or less took the same
code from the example in the book):

SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
Date refDate = formatter.parse("2013-01-15");

HTableInterface toyDataTable = pool.getTable("ToyDataTable");

byte[] md5Key = md5( refDate.getTime() +"" );
int md5Length = 16;
int longLength = 8;
byte[] startRow = Bytes.padTail( md5Key, longLength );
byte[] endRow = Bytes.padTail( md5Key, longLength );
endRow[md5Length-1]++;

Scan scan = new Scan( startRow, endRow );
ResultScanner rs = toyDataTable.getScanner( scan );
for( Result r : rs ) {
String value =  Bytes.toString( r.getValue( Bytes.toBytes("CF"),
Bytes.toBytes("SampleCol")) );
System.out.println( value );
}

The result is empty. How is that possible?
+
Paul van Hoven 2013-02-19, 19:13