On every Get, BloomFilter is acting as a filter (!) on top of each HFile and allows to check if a key is absent from the HFile. So yes, you will benefit from these filters.
On Fri, Jan 4, 2013 at 8:58 PM, Jean-Marc Spaggiari <[email protected] > wrote: > Is KeyOnlyFilter using the BloomFilters too? > > Here is, with more details, what I'm doing. > > Few questions. > - Can I create one single KeyOnlyFilter and give the same filter to > all the gets? > - Will bloom filters benefit in such scenario? My key is small. Let's > say average 128 bytes. > > The goal here is to check about 500 entries at a time to validate if > they already exist or not. > > In my MR, I'm starting when I have more than 100K lines to handle, and > each line car have up to 1K entries. So it can result up to 100M > gets... Job took initially 500 minutes to complete. I have added few > pretty good nodes and it's not taking less than 300 minutes. But I > would like to get under 100 minutes if I can... > > Thanks, > > JM > > Vector<Get> gets_entry_exist = new Vector<Get>(); > for (Entry entry : entries.getEntries()) > { > Get entry_exist = new Get(entry.toKey()); > entry_exist.setFilter(new KeyOnlyFilter()); > gets_entry_exist.add(entry_exist); > } > > Result[] result_entry_exist = table_entry.get(gets_entry_exist); > > int index = 0; > for (Entry entry : entries.getEntries()) > { > boolean isEmpty = result_entry_exist[index++].isEmpty(); > if (isEmpty) > { > // Process here > } > } > { > > > 2013/1/4, Damien Hardy <[email protected]>: > > Hello Jean-Marc, > > > > BloomFilters are just designed for that. > > > > But they say if a row doesn't exist with a ash of the key (not the > oposit, > > 2 rowkeys could have the same ash result). > > > > If you want to be sure the rowkey exists you have to search for it in the > > HFile ( the whole mechanism is transparent with the get() ). > > > > Their is also an KeOnlyFilter > > > http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/filter/KeyOnlyFilter.html > > preventing from getting the whole columns of the existing key as return > > (which could be heavy). > > > > Cheers, > > > > -- > > Damien > > > > > > 2013/1/4 Jean-Marc Spaggiari <[email protected]> > > > >> Hi, > >> > >> What's the fastest way to know if a row exist? > >> > >> Today I'm doing that: > >> > >> Get get_entry_exist = new Get(key).addColumn(CF_DATA, C_DATA); > >> Result entry_exist = table_entry.get(get_entry_exist); > >> > >> But should this be faster? > >> Get get_entry_exist = new Get(key); > >> Result entry_exist = table_entry.get(get_entry_exist); > >> > >> There is only one CF and one C on my table. > >> > >> Or is there an even faster way? > >> > >> Also, is there a way to make that even faster? I think BloomFilters > >> can help, right? > >> > >> Thanks, > >> > >> JM > >> > > > -- Adrien Mogenet 06.59.16.64.22 http://www.mogenet.me
