Sever, I'd say that the wiki page is incomplete when discussing bloom filters. The HBase Reference Guide
http://hbase.apache.org/book.html#schema.bloom provides a much better explanation of the different bloom filter options. ~ Minh On Thu, Jun 28, 2012 at 9:54 AM, Sever Fundatureanu <[email protected]> wrote: > Thanks, Minh. > This blog also mentions that bloom filters check "if a given column exists > in a given row". However in "HBase: The definitive guide" it is mentioned > that "enabling the Bloom filter does give you the immediate advantage of > knowing if a file contains a particular row key or not". Is the blog post a > bit outdated? > > Thanks, > Sever > > > On Wed, Jun 27, 2012 at 6:00 PM, Minh Duc Nguyen <[email protected]> wrote: > >> Sever, the IN_MEMORY option doesn't change when table content is >> transferred into RAM. Whether set to true or false, the blocks of >> data are only loaded into memory after a normal retrieval operation. >> When IN_MEMORY is set to true, HBase just tries to keep data in memory >> more aggressively than it normally would. This wiki explains it in >> more detail: >> >> >> http://jimbojw.com/wiki/index.php?title=Understanding_HBase_column-family_performance_options >> >> ~ Minh >> >> On Wed, Jun 27, 2012 at 7:18 AM, Sever Fundatureanu >> <[email protected]> wrote: >> > Hello, >> > >> > I initially created a table without the IN_MEMORY option enabled and >> loaded >> > some data into it. Then I disabled it, modified the IN_MEMORY option >> using >> > the hbase shell 'alter' command, re-enabled it and finally ran a major >> > compaction. I do notice now the memory usage of the region servers has >> > increased. However for some queries I am still getting faster responses >> > only the 2nd time, as if I'm hitting the cache. Can someone tell me when >> > does the table content get transferred into RAM if IN_MEMORY option is >> > enabled like above? >> > >> > Thank you, >> > -- >> > Sever Fundatureanu >> > >> > Vrije Universiteit Amsterdam >> > E-mail: [email protected] >> > > > > -- > Sever Fundatureanu > > Vrije Universiteit Amsterdam > Tel: +31644329534 > E-mail: [email protected]
