Title: Apache Accumulo Export/Import Example
Notice:    Licensed to the Apache Software Foundation (ASF) under one
           or more contributor license agreements.  See the NOTICE file
           distributed with this work for additional information
           regarding copyright ownership.  The ASF licenses this file
           to you under the Apache License, Version 2.0 (the
           "License"); you may not use this file except in compliance
           with the License.  You may obtain a copy of the License at
           .
             http://www.apache.org/licenses/LICENSE-2.0
           .
           Unless required by applicable law or agreed to in writing,
           software distributed under the License is distributed on an
           "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
           KIND, either express or implied.  See the License for the
           specific language governing permissions and limitations
           under the License.

Accumulo provides a mechanism to export and import tables. This README shows
how to use this feature.

The shell session below shows creating a table, inserting data, and exporting
the table. A table must be offline to export it, and it should remain offline
for the duration of the distcp. An easy way to take a table offline without
interuppting access to it is to clone it and take the clone offline.

    root@test15> createtable table1
    root@test15 table1> insert a cf1 cq1 v1
    root@test15 table1> insert h cf1 cq1 v2
    root@test15 table1> insert z cf1 cq1 v3
    root@test15 table1> insert z cf1 cq2 v4
    root@test15 table1> addsplits -t table1 b r
    root@test15 table1> scan
    a cf1:cq1 []    v1
    h cf1:cq1 []    v2
    z cf1:cq1 []    v3
    z cf1:cq2 []    v4
    root@test15> config -t table1 -s table.split.threshold=100M
    root@test15 table1> clonetable table1 table1_exp
    root@test15 table1> offline table1_exp
    root@test15 table1> exporttable -t table1_exp /tmp/table1_export
    root@test15 table1> quit

After executing the export command, a few files are created in the hdfs dir.
One of the files is a list of files to distcp as shown below.

    $ hadoop fs -ls /tmp/table1_export
    Found 2 items
    -rw-r--r--   3 user supergroup        162 2012-07-25 09:56 /tmp/table1_export/distcp.txt
    -rw-r--r--   3 user supergroup        821 2012-07-25 09:56 /tmp/table1_export/exportMetadata.zip
    $ hadoop fs -cat /tmp/table1_export/distcp.txt
    hdfs://n1.example.com:6093/accumulo/tables/3/default_tablet/F0000000.rf
    hdfs://n1.example.com:6093/tmp/table1_export/exportMetadata.zip

Before the table can be imported, it must be copied using distcp. After the
discp completed, the cloned table may be deleted.

    $ hadoop distcp -f /tmp/table1_export/distcp.txt /tmp/table1_export_dest

The Accumulo shell session below shows importing the table and inspecting it.
The data, splits, config, and logical time information for the table were
preserved.

    root@test15> importtable table1_copy /tmp/table1_export_dest
    root@test15> table table1_copy
    root@test15 table1_copy> scan
    a cf1:cq1 []    v1
    h cf1:cq1 []    v2
    z cf1:cq1 []    v3
    z cf1:cq2 []    v4
    root@test15 table1_copy> getsplits -t table1_copy
    b
    r
    root@test15> config -t table1_copy -f split
    ---------+--------------------------+-------------------------------------------
    SCOPE    | NAME                     | VALUE
    ---------+--------------------------+-------------------------------------------
    default  | table.split.threshold .. | 1G
    table    |    @override ........... | 100M
    ---------+--------------------------+-------------------------------------------
    root@test15> tables -l
    accumulo.metadata    =>        !0
    accumulo.root        =>        +r
    table1_copy          =>         5
    trace                =>         1
    root@test15 table1_copy> scan -t accumulo.metadata -b 5 -c srv:time
    5;b srv:time []    M1343224500467
    5;r srv:time []    M1343224500467
    5< srv:time []    M1343224500467