I've added this information to my "Data Distribution Throughout the Accumulo Cluster" page at https://github.com/medined/D4M_Schema/blob/master/docs/data_distribution.md#user-content-example-of-splits-inside-the-metadata-table.
On Tue, Jun 24, 2014 at 11:13 PM, Eric Newton <[email protected]> wrote: > That's an excellent idea. I would still like to distill the information > into a talk, but it would be nice if the information was also in the code. > > > > > On Tue, Jun 24, 2014 at 10:53 PM, Sean Busbey <[email protected]> wrote: >> >> Couldn't we add this kind of documentation to e.g. the MetadataSchema >> class? >> >> Or some developer focuses architecture docs? >> >> >> >> On Jun 24, 2014 9:48 PM, "Eric Newton" <[email protected]> wrote: >> > >> > "<" means no end-row. It's the last tablet, which is often called the >> > default tablet. >> > >> > So, >> > >> >> 3p< ~tab:~pr \x00 >> > >> > >> > You can decode this as a tablet covering (-inf, +inf) for tablet id 3p. >> > >> >> 3p;a ~tab:~pr \x00 >> >> 3p;m ~tab:~pr \x01a >> >> 3p;z ~tab:~pr \x01m >> >> 3p< ~tab:~pr \x01z >> > >> > >> > This table, id "3p" has splits: (-inf, a], (a, m], (m, z], (z, +inf). >> > "pr" stands for "end-row of previous tablet", which we often shorten to >> > "prevrow". Tilde's sort late in UTF8, which is important for some race >> > conditions when a table is splitting. >> > >> > I'm putting together a new presentation on the decoding of the metadata >> > tables. I need to get the presentation approved by my colleagues, so it's >> > going to be some time before it is ready. I would like to write a shell >> > Formatter that would make the metadata more more human friendly. >> > >> > If you have any other questions about the metadata table, please ask. >> > I'll make sure the answers are in the presentation. >> > >> > -Eric >> > >> > >> > >> > >> > On Tue, Jun 24, 2014 at 10:21 PM, William Slacum >> > <[email protected]> wrote: >> >> >> >> < is a byte used for doing an ordering on rows that share the same >> >> prefix. >> >> >> >> There was a presentation floating around on the specifics of the >> >> metadata table at one point. I believe that helps tablet information sort >> >> before the last tablet, which is suffixed with '~', to force it to sort >> >> after the other tablets. We'll probably get an Eric or Keith email soon >> >> laying down the law, but that's what I remember. >> >> >> >> >> >> On Tue, Jun 24, 2014 at 9:57 PM, Dickson, Matt MR >> >> <[email protected]> wrote: >> >>> >> >>> UNOFFICIAL >> >>> >> >>> When looking up rfile references in the metadata table we normally see >> >>> <tableid>;<range> for the rowid. I've noticed some rowids are >> >>> <tableid>< >> >>> eg. 3p< >> >>> >> >>> Is this because the table is small and hasn't been split or some other >> >>> reason? >> >> >> >> >> > > >
