Hmm seems like we need to bundle the doc for each release. For example, the 4.0.0 does not have HBase store.
Most projects have docs for each release on top of project homepage, like Zookeeper http://zookeeper.apache.org/doc/r3.4.6/ or Spark http://spark.apache.org/docs/0.9.0/ Thoughts? - Henry On Mon, Mar 24, 2014 at 2:50 PM, Kasper Sørensen <[email protected]> wrote: > Hmm I suppose a wiki page would be good. I guess we have wiki pages for > some of the DataContext implementations already like Salesforce [1], POJO > [2] and Composite [3] ... Maybe we should even have a page for *every > *DataContext > implementation there is, simply for completeness and referenceability of > documentation. > > [1] http://wiki.apache.org/metamodel/examples/SalesforceDataContext > [2] http://wiki.apache.org/metamodel/examples/PojoDataContext > [3] http://wiki.apache.org/metamodel/examples/CompositeDataContext > > > 2014-03-24 22:44 GMT+01:00 Henry Saputra <[email protected]>: > >> Ok +1 >> >> How do you propose to document this feature? As another page in the >> doc svn repo? >> >> - Henry >> >> On Mon, Mar 24, 2014 at 2:42 PM, Kasper Sørensen >> <[email protected]> wrote: >> > Yep. Or in slightly more technical terms: It means that the >> > HBaseDataContext only implements DataContext which has these two >> > significant methods: >> > >> > * getSchemas() >> > * executeQuery(...) >> > >> > (Plus a bunch more methods, but those two give you the general >> impression: >> > Explore metadata and fire queries / reads) >> > But not UpdateableDataContext, which has the write operations: >> > >> > * executeUpdate(...) >> > >> > Regards, >> > Kasper >> > >> > >> > 2014-03-24 22:37 GMT+01:00 Henry Saputra <[email protected]>: >> > >> >> Hmm, what does it mean by read only? You can use it to read data from >> >> HBase? >> >> >> >> - Henry >> >> >> >> On Mon, Mar 24, 2014 at 2:34 PM, Kasper Sørensen >> >> <[email protected]> wrote: >> >> > A quick update on this since the module has now been merged into the >> >> master >> >> > branch: >> >> > >> >> > 1) Module is still read-only. This is accepted for now (unless someone >> >> > wants to help change it of course). >> >> > >> >> > 2) Metadata mapping is still working in two modes: a) we discover the >> >> > column families and expose them as byte-array maps (not very useful, >> but >> >> > works as a "lowest common denominator") and b) the user provides a >> set of >> >> > SimpleTableDef (which now has a convenient parser btw.:)) and gets his >> >> > table mapping as he wants it. >> >> > >> >> > 3) Querying now has special support for lookup-by-id type queries >> where >> >> we >> >> > will use HBase Get instead of Scan. We also have good support for >> >> > LIMIT/"maxRows", but not OFFSET/"firstRow" (in those cases we will >> scan >> >> > past the first records on the client side). >> >> > >> >> > 4) Dependencies seems to be a pain still. HBase and Hadoop comes in >> many >> >> > flavours and all are not compatible. I doubt there's a lot we can do >> >> about >> >> > it, except ask the users to provide their own HBase dependency as per >> >> their >> >> > backend version. We should probably thus make all our HBase/Hadoop >> >> > dependencies <optional>true</optional> in order to not influence the >> >> > typical clients. >> >> > >> >> > Kasper >> >> > >> >> > >> >> > 2014-02-24 17:08 GMT+01:00 Kasper Sørensen < >> >> [email protected]>: >> >> > >> >> >> Hi Henry, >> >> >> >> >> >> Yea the Phoenix project is definately an interesting approach to >> making >> >> MM >> >> >> capable of working with HBase. The only downside to me is that it >> seems >> >> >> they do a lot of intrusive stuff to HBase like creating new index >> tables >> >> >> etc... I would normally not "allow" that for a simple connector. >> >> >> >> >> >> Maybe we should simply support both styles. And in the case of >> Phoenix, >> >> I >> >> >> guess we could simply go through the JDBC module of MetaModel and >> >> connect >> >> >> via their JDBC driver... Is that maybe a route, do you know? >> >> >> >> >> >> - Kasper >> >> >> >> >> >> >> >> >> 2014-02-24 6:37 GMT+01:00 Henry Saputra <[email protected]>: >> >> >> >> >> >> We could use the HBase client library from the store I suppose. >> >> >>> The issue I am actually worry is actually adding real query support >> >> >>> for column based datastore is kind of big task. >> >> >>> Apache Phoenix tried to do that so maybe we could leverage the SQL >> >> >>> planner layer to provide the implementation of the query execution >> to >> >> >>> HBase layer? >> >> >>> >> >> >>> - Henry >> >> >>> >> >> >>> >> >> >>> On Mon, Feb 17, 2014 at 9:33 AM, Kasper Sørensen >> >> >>> <[email protected]> wrote: >> >> >>> > Thanks for the input Henry. With your experience, do you then also >> >> >>> happen >> >> >>> > to know of a good thin client-side library? I imagine that we >> could >> >> >>> maybe >> >> >>> > use a REST client instead of the full client we currently use. >> That >> >> >>> would >> >> >>> > save us a ton of dependency-overhead I think. Or is it a >> non-issue in >> >> >>> your >> >> >>> > mind, since HBase users are used to this overhead? >> >> >>> > >> >> >>> > >> >> >>> > 2014-02-16 7:16 GMT+01:00 Henry Saputra <[email protected] >> >: >> >> >>> > >> >> >>> >> For 1 > I think adding read only to HBase should be ok because >> most >> >> >>> >> update to HBase either through HBase client or REST via Stargate >> [1] >> >> >>> >> or Thrift >> >> >>> >> >> >> >>> >> For 2 > In Apache Gora we use Avro to do type mapping to column >> and >> >> >>> >> generate POJO java via Avro compiler. >> >> >>> >> >> >> >>> >> For 3 > This is the one I am kinda torn. Apache Phoenix >> incubating >> >> try >> >> >>> >> to provide SQL to HBase [2] via extra indexing and caching. I >> think >> >> >>> >> this is defeat the purpose of having NoSQL databases that serve >> >> >>> >> different purpose than Relational databse. >> >> >>> >> >> >> >>> >> I am not sure Metamodel should touch NoSQL databases which more >> like >> >> >>> >> column types. These databases are designed for large data with >> >> access >> >> >>> >> primary via key and not query mechanism. >> >> >>> >> >> >> >>> >> Just my 2-cent >> >> >>> >> >> >> >>> >> >> >> >>> >> [1] http://wiki.apache.org/hadoop/Hbase/Stargate >> >> >>> >> [2] http://phoenix.incubator.apache.org/ >> >> >>> >> >> >> >>> >> On Fri, Jan 24, 2014 at 11:35 AM, Kasper Sørensen >> >> >>> >> <[email protected]> wrote: >> >> >>> >> > Hi everyone, >> >> >>> >> > >> >> >>> >> > I was looking at our "hbase-module" branch and as much as I >> like >> >> this >> >> >>> >> idea, >> >> >>> >> > I think we've been a bit too idle with the branch. Maybe we >> should >> >> >>> try to >> >> >>> >> > make something final e.g. for a version 4.1. >> >> >>> >> > >> >> >>> >> > So I thought to give an overview/status of the module's current >> >> >>> >> > capabilities and it's shortcomings. We should figure out if we >> >> think >> >> >>> this >> >> >>> >> > is good enough for a first version, or if we want to do some >> >> >>> improvements >> >> >>> >> > to the module before adding it to our portfolio of MetaModel >> >> modules. >> >> >>> >> > >> >> >>> >> > 1) The module only offers read-only/query access to HBase. >> That is >> >> >>> in my >> >> >>> >> > opinion OK for now, we have several such modules, and this is >> >> >>> something >> >> >>> >> we >> >> >>> >> > can better add later if we straighten out the remaining topics >> in >> >> >>> this >> >> >>> >> mail. >> >> >>> >> > >> >> >>> >> > 2) With regards to metadata mapping: HBase is different >> because it >> >> >>> has >> >> >>> >> both >> >> >>> >> > column families and in column families there are columns. For >> the >> >> >>> sake of >> >> >>> >> > our view on HBase I would describe column families simply as "a >> >> >>> logical >> >> >>> >> of >> >> >>> >> > columns". Column families are fixed within a table, but rows >> in a >> >> >>> table >> >> >>> >> may >> >> >>> >> > contain arbitrary numbers of columns within each column family. >> >> >>> So... You >> >> >>> >> > can instantiate the HBaseDataContext in two ways: >> >> >>> >> > >> >> >>> >> > 2a) You can let MetaModel discover the metadata. This >> >> unfortunately >> >> >>> has a >> >> >>> >> > severe limitation. We discover the table names and column >> families >> >> >>> using >> >> >>> >> > the HBase API. But the actual columns and their contents >> cannot be >> >> >>> >> provided >> >> >>> >> > by the API. So instead we simply expose the column families >> with a >> >> >>> MAP >> >> >>> >> data >> >> >>> >> > types. The trouble with this is that the keys and values of the >> >> maps >> >> >>> will >> >> >>> >> > simply be byte-arrays ... Usually not very useful! But it's >> sort >> >> of >> >> >>> the >> >> >>> >> > only thing (as far as I can see) that's "safe" in HBase, since >> >> HBase >> >> >>> >> allows >> >> >>> >> > anything (byte arrays) in it's columns. >> >> >>> >> > >> >> >>> >> > 2b) Like in e.g. MongoDb or CouchDb modules you can provide an >> >> array >> >> >>> of >> >> >>> >> > tables (SimpleTableDef). That way the user defines the metadata >> >> >>> himself >> >> >>> >> and >> >> >>> >> > the implementation assumes that it is correct (or else it will >> >> >>> break). >> >> >>> >> The >> >> >>> >> > good thing about this is that the user can define the proper >> data >> >> >>> types >> >> >>> >> > etc. for columns. The user defines the column family and column >> >> name >> >> >>> by >> >> >>> >> > setting defining the MetaModel column name as this: >> "family:name" >> >> >>> >> > (consistent with most HBase tools and API calls). >> >> >>> >> > >> >> >>> >> > 3) With regards to querying: We've implemented basic query >> >> >>> capabilities >> >> >>> >> > using the MetaModel query postprocessor. But not all queries >> are >> >> very >> >> >>> >> > effective... In addition to of course full table scans, we have >> >> >>> optimized >> >> >>> >> > support of of COUNT queries and of table scans with maxRows. >> >> >>> >> > >> >> >>> >> > We could rather easily add optimized support for a couple of >> other >> >> >>> >> typical >> >> >>> >> > queries: >> >> >>> >> > * lookup record by ID >> >> >>> >> > * paged table scans (both firstRow and maxRows) >> >> >>> >> > * queries with simple filters/where items >> >> >>> >> > >> >> >>> >> > 4) With regards to dependencies: The module right now depends >> on >> >> the >> >> >>> >> > artifact called "hbase-client". This dependency has a loot of >> >> >>> transient >> >> >>> >> > dependencies so the size of the module is quite extreme. As an >> >> >>> example, >> >> >>> >> it >> >> >>> >> > includes stuff like jetty, jersey, jackson and of course >> hadoop... >> >> >>> But I >> >> >>> >> am >> >> >>> >> > wondering if we can have a more thin client-side than that! If >> >> anyone >> >> >>> >> knows >> >> >>> >> > if e.g. we can use the REST interface easily or so, that would >> >> maybe >> >> >>> be >> >> >>> >> > better. I'm not an expert on HBase though, so please enlighten >> me! >> >> >>> >> > >> >> >>> >> > Kind regards, >> >> >>> >> > Kasper >> >> >>> >> >> >> >>> >> >> >> >> >> >> >> >> >>
