rowcounter does not return the correct number of rows in certain circumstances
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Key: HBASE-4295
URL: https://issues.apache.org/jira/browse/HBASE-4295
Project: HBase
Issue Type: Bug
Components: mapreduce
Affects Versions: 0.90.4
Reporter: Wing Yew Poon
When you run
{noformat}
hadoop jar hbase.jar rowcounter <table>
{noformat}
the org.apache.hadoop.hbase.mapreduce.RowCounter class is run.
The RowCounterMapper class in the RowCounter mapreduce job contains the
following:
{noformat}
@Override
public void map(ImmutableBytesWritable row, Result values,
Context context)
throws IOException {
for (KeyValue value: values.list()) {
if (value.getValue().length > 0) {
context.getCounter(Counters.ROWS).increment(1);
break;
}
}
}
{noformat}
The intention is to go through the column values in the row, and increment the
ROWS counter if some value is non-empty. However, values.list() always has size
1. This is because the createSubmittableJob static method uses a Scan as
follows:
{noformat}
Scan scan = new Scan();
scan.setFilter(new FirstKeyOnlyFilter());
{noformat}
So the input map splits always contain just the first KV. If the column
corresponding to that first KV is empty, even though other columns are
non-empty, that row is skipped.
This way, rowcounter can return an incorrect result.
One way to reproduce this is to create an hbase table with two columns, say
f1:q1 and f2:q2. Create some (say 2) rows with empty f1:q1 but non-empty f2:q2,
and some (say 3) rows with empty f2:q2 and non-empty f1:q1.
Then run rowcounter (specifying only the table but not any columns). The count
will be either 2 short or 3 short.
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