Changes between Initial Version and Version 1 of hadoop_hbase_sample1

Timestamp:

Jun 3, 2008, 6:27:22 PM (18 years ago)

Author:

waue

Comment:

--

hadoop_hbase_sample1

@@ +1 @@
+ = Sample Code of Show Hbase Write&Read by Map-Reduce " = 
+ == Abstract == 
+The demo program will insert values to " Column Family: Column Identify" and then print these.
+
+ *  pre-do : create a hbase table "test_table" with (CF:CI) which (" column family ", " column ID ")  [[BR]]
+
+ 1 $ bin/hbase shell [[BR]]
+ 2 > create table test_table("CF"); [[BR]]
+ ok ! we can test it  [[BR]]
+ 3 > insert into test_table("CF:CI") values=("Hellow World") where row = "1"; [[BR]]
+ 4 > select * from test_table;  [[BR]]
+{{{
+08/06/03 16:16:36 INFO hbase.HTable: Creating scanner over test_table starting at key 
++---------+-----------+-----------+
+| Row                   | Column                  | Cell                     |
++---------+-----------+-----------+
+| 1                        | CF:CI                     | Hellow World      |
++---------+-----------+-----------+
+1 row(s) in set. (0.24 sec)
+}}}
+
+ on the  structure , '''Row''' means Row ID which is a key to describe a column; [[br]]
+ '''Column''' means the database structure in test_table, [[br]]
+ Column Family , "CF",  should be defined while creating table. [[br]]
+ Column Id , "CI" , can be added dynamically. [[br]]
+ '''Cell''' is the value of CF:CI [[br]]
+
+ == Output == 
+
+ That's the structure; then the demo program will show you in console as below :
+
+{{{
+Illustration of adding data...
+Writing row = 0, col 'CF:CI' = Hellow0
+Writing row = 1, col 'CF:CI' = Hellow1
+Writing row = 2, col 'CF:CI' = Hellow2
+Writing row = 3, col 'CF:CI' = Hellow3
+Writing row = 4, col 'CF:CI' = Hellow4
+Writing row = 5, col 'CF:CI' = Hellow5
+Writing row = 6, col 'CF:CI' = Hellow6
+Writing row = 7, col 'CF:CI' = Hellow7
+Writing row = 8, col 'CF:CI' = Hellow8
+Writing row = 9, col 'CF:CI' = Hellow9
+
+Illustration of querying...
+row = 1, 'CF : CI ' = Hellow1
+
+Illustration of scanning...
+08/06/03 16:47:51 INFO hbase.HTable: Creating scanner over test_table starting at key 
+row = 0//9223372036854775807, col 'CF:CI' = Hellow0
+row = 1//9223372036854775807, col 'CF:CI' = Hellow1
+row = 2//9223372036854775807, col 'CF:CI' = Hellow2
+row = 3//9223372036854775807, col 'CF:CI' = Hellow3
+row = 4//9223372036854775807, col 'CF:CI' = Hellow4
+row = 5//9223372036854775807, col 'CF:CI' = Hellow5
+row = 6//9223372036854775807, col 'CF:CI' = Hellow6
+row = 7//9223372036854775807, col 'CF:CI' = Hellow7
+row = 8//9223372036854775807, col 'CF:CI' = Hellow8
+row = 9//9223372036854775807, col 'CF:CI' = Hellow9
+}}}
+
+ == code == 
+
+{{{
+/*
+ *  DemoHBaseClient.java
+ */
+
+// package tw.org.nchc.demo;
+
+import java.io.IOException;
+import java.util.SortedMap;
+import java.util.TreeMap;
+
+import org.apache.hadoop.hbase.HBaseConfiguration;
+import org.apache.hadoop.hbase.HScannerInterface;
+import org.apache.hadoop.hbase.HStoreKey;
+import org.apache.hadoop.hbase.HTable;
+import org.apache.hadoop.io.Text;
+
+
+public class DemoHBaseClient {
+
+        public static void main(String[] args) throws IOException {
+
+                // Open the "test_table" table. If it hasn't been in Hbase, you should create.
+                HBaseConfiguration conf = new HBaseConfiguration();
+                HTable table = new HTable(conf, new Text("test_table"));
+        
+                System.out.println("Illustration of adding data...");
+
+                // create column formed  (Column Family:Column Id)
+                Text column = new Text("CF:CI");
+
+                // create row_id 
+                Text row_id = new Text();
+
+                // demo 1  : Insert ten demo values
+                for (int i = 0; i < 10; i++) {
+                        
+                        // give row_id  value
+                        row_id.set(new Integer(i).toString());
+                        
+                        // let "indicate_id" indicate the column which row = row_id
+                        long indicate_id= table.startUpdate(row_id);
+                        
+                        //val =  value of CF:CI where row_id = i
+                        Text val = new Text("Hellow" + i);
+
+                        // put "val" to "column" from "table" where "row_id"
+                        // the same as :  
+                        // hql> INSERT INTO table( column ) VALUES=( val) WHERE ROW = row_id ;
+                        table.put(indicate_id, column, val.getBytes());
+                        table.commit(indicate_id);
+
+                        System.out.println("Writing row = " + row_id + ", col '" + column
+                                        + "' = " + val);
+                }
+
+                // demo 2 : print column value only row = 1 ;
+                System.out.println("\n Querying row = 1");
+                
+                // Get a single value for the specified row and column
+                // byte[] = HTable.get(Text row, Text column)
+                
+                String s = Text.decode(table.get(new Text("1"),new Text("CF:CI")));
+                // if change as  
+                // String s = (table.get(new Text("1"),new Text("CF:CI"))).toString();
+                // will get chaos code "  [B@1f14ceb"
+                System.out.println("row = 1, 'CF : CI ' = " + s);
+
+                // demo 3 :  Print the all contents of this table
+                System.out.println("\nIllustration of scanning...");
+
+                // we only want one column, but you can specify multiple columns to
+                // fetch at once
+                Text[] cols = { column };
+
+                // Use HScannerInterface to crawl table
+                HScannerInterface scanner = table.obtainScanner(cols, new Text());
+
+                // column values are stored in a Map
+                SortedMap<Text, byte[]> values = new TreeMap<Text, byte[]>();
+                HStoreKey currentKey = new HStoreKey();
+                while (scanner.next(currentKey, values)) {
+                        // decode the stored byte[] back into a String
+                        String val = Text.decode(values.get(column));
+                        System.out.println("row = " + currentKey + ", col '" + column + "' = "
+                                        + val);
+                }
+
+                // remember to close scanner when done
+                scanner.close();
+
+        }
+
+}
+
+}}}