The TimestampFilter will return only the Keys whose timestamp fall in
the range you specify. The timestamp is an attribute on every Key, a
long value which, when not set by the client at write time, is the
number of millis since the epoch. You specify the numeric range of
timestamps you want. This is a post-filter operation -- Accumulo must
still read all of the data in the table.
You need to tell *us* what the time component you're actually filtering
on: the timestamp on each Key, or the createdDate column in each row.
MapReduce is likely more efficient to do this batch processing (as
MapReduce is a batch processing system). See the AccumuloInputFormat class.
Bob Cook wrote:
I'm new to accumulo and inherited this project to extract all data from
accumulo (assembled as a "document" by RowID) into another web service.
So I started with SimpleReadClient.java to "scan" all data, and built a
"document" based on the RowID, ColumnFamily and Value. Sending
this "document" to the service.
ID CF CV
RowID_1 createdDate "2015-01-01:00:00:01 UTC"
RowID_1 data "this is a test"
RowID_1 title "My test title"
RowID_2 createdDate "2015-01-01:12:01:01 UTC"
RowID_2 data "this is test 2"
RowID_2 title "My test2 title"
So my table is pretty simple, RowID, ColumnFamily and Value (no
I need to process one Billion "OLD" unique RowIDs (a years worth of
data) on a live system that is ingesting "new data" at a rate of about a
4million RowIds a day.
i.e. I need to process data from September 2015 - September 2016, not
worrying about new data coming in.
So I'm thinking I need to run multiple processes to extract ALL the data
in this "data range" to be more efficient.
Also, it may allow me to run the processes at a lower priority and at
off-hours of the day when traffic is less.
My issue is how do I specify the "range" to scan, and how do I specify.
1. Is using the "createdDate" a good idea, if so how would I specify the
range for it.
2. How about the TimestampFilter? If I specify my start to end to
"equal" a day (about 4 Million unique RowIDs),
Will this get me all ColumnFamily and Values for a given RowID? Or
could I miss something because it's timestamp
was the next day. I don't really understand Timestamps wrt Accumulo.
3. Does a map-reduce job make sense. If so, how would I specify.