Good info Edward. Thanks. Thanks, Ranjith
On May 13, 2012, at 2:33 PM, Edward Capriolo <edlinuxg...@gmail.com> wrote: > The original design docs say you can not build indexes on external tables but > I tried it in 0.8.x and confirmed you can. > > On Sunday, May 13, 2012, Ranjith <ranjith.raghunat h...@gmail.com> wrote: > > Indexes can be built on tables managed by hive. For external tables I do > > not believe that to be true. Please feel to correct if I am wrong. > > > > Thanks, > > Ranjith > > On May 12, 2012, at 9:24 PM, Nanda Vijaydev <nanda.vijay...@gmail.com> > > wrote: > > > > In hive, the raw data is in HDFS and there is a metadata layer that defines > > the structure of the raw data. Table is usually a reference to metadata, > > probably in a mySQL server and it contains a reference to the location of > > the data in HDFS, type of delimiter or serde to use and so on. > > 1. With hive managed tables, when you drop a table, both the metadata in > > mysql and raw data on the cluster gets deleted. > > 2. With external tables, when you drop a table, just the metadata gets > > deleted and the raw data continues to exist on the cluster. > > > > On Thu, May 10, 2012 at 3:02 PM, David Kulp <dk...@fiksu.com> wrote: > >> > >> It's simpler than this. All files look the same -- and are often very > >> simple delimited text -- whether managed or external. The only difference > >> is that the files associated with a managed table are dropped when the > >> table is dropped and files that are loaded into a managed table are moved > >> into hive's private path. External tables never move or remove files. > >> Performance is the same. > >> > >> On May 10, 2012, at 5:52 PM, kulkarni.swar...@gmail.com wrote: > >> > >> > I am pretty new to hive and was trying to clearly understand the > >> > difference between a managed and an external table. > >> > > >> > As my current understanding stands, a managed table is a table whose > >> > data is completely owned by hive whereas an external table is usually > >> > created to have a hive frontend for the data managed in external > >> > systems.I would suppose this would mean that a query on an external > >> > table goes out to fetch data from the given external table, deserialize > >> > according to the given/suitable SerDe and then show the output of the > >> > query in hive format. > >> > > >> > So does this mean that cost of using external tables is much higher than > >> > the native ones? Or is there some caching that comes into play that I am > >> > not seeing right now. > >> > > >> > Thanks for the help. > >> > > >> > -- > >> > Swarnim > >> > > > >
