Question

I want to empty a table in hbase… eg: user. Is there any command or function to empty the table without deleting it…

My table structure is :

$mutations = array(
                new Mutation( array(
                    'column' => 'username:1',
                    'value' =>$name
                ) ),
                new Mutation( array(
                    'column' => 'email:1',
                    'value' =>$email
                ) )
        );          
$hbase->mutateRow("user",$key,$mutations);

Can someone help me?

Answer 1

There’s no single command to clear Hbase table, but you can use 2 workarounds: disable, delete, create table, or scan all records and delete each.

Actually, disable, delete and create table again takes about 4 seconds.

// get Hbase client
$client = <Your code here>;
$t = "table_name";

$tables = $client->getTableNames();

if (in_array($t, $tables)) {
  if ($client->isTableEnabled($t))
    $client->disableTable($t);

  $client->deleteTable($t);
}

$descriptors = array(
  new ColumnDescriptor(array("name" =>  "c1", "maxVersions" => 1)),
  new ColumnDescriptor(array("name" =>  "c2", "maxVersions" => 1))
);

$client->createTable($t, $descriptors);

If there’s not a lot of data in table – scan all rows and delete each is much faster.

$client = <Your code here>;
$t = "table_name";

// i don't remember, if list of column families is actually needed here
$columns = array("c1", "c2");

$scanner = $client->scannerOpen($t, "", $columns);
while ($result = $client->scannerGet($scanner)) {
  $client->deleteAllRow($t, $result[0]->row);
}

In this case data is not deleted physically, actually it’s “marked as deleted” and stays in table until next major compact.