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Pig, mail # user - String Representation of DataBag and its Schema


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Re: String Representation of DataBag and its Schema
Jonathan Coveney 2013-03-19, 15:43
How are you planning on generating these cases? By hand? Or automated?
2013/3/19 Dan DeCapria, CivicScience <[EMAIL PROTECTED]>

> String string_databag in this example was typed out by me, as the input
> String for a JUnit test method. I am considering generating many of these
> for case specific unit testing of my UDFs.
>
> -Dan
>
> On Tue, Mar 19, 2013 at 11:27 AM, Jonathan Coveney <[EMAIL PROTECTED]
> >wrote:
>
> > how was string_databag generated?
> >
> >
> > 2013/3/19 Dan DeCapria, CivicScience <[EMAIL PROTECTED]>
> >
> > > Expanding upon this, the following use case's Schema Object can be
> > resolved
> > > from inputs:
> > >
> > >         String string_databag = "{(a,(b,d),f)}";
> > >         String string_schema > > > "b1:bag{t1:tuple(a:chararray,t2:tuple(b:chararray,d:long),f:long)}";
> > >         Schema schema = Utils.getSchemaFromString(string_schema);
> > >
> > > Next step is to resolve a DataBag Object from String string_databag and
> > the
> > > Schema Object.
> > >
> > > -Dan
> > >
> > > On Tue, Mar 19, 2013 at 9:37 AM, Dan DeCapria, CivicScience <
> > > [EMAIL PROTECTED]> wrote:
> > >
> > > > Thank you for your reply.
> > > >
> > > > The problem is I cannot find a methodology to go from a String
> > > > representation of a complex data type to a nested Object of pig
> > > DataTypes.
> > > > I looked over the pig 0.10.1 docs, but cannot find a way to go from
> > > String
> > > > and Schema to pig DataType Object.
> > > >
> > > > For context, I am generating these Strings for my own JUnit testing
> of
> > > > other UDFs.  Currently, for complex types, I have to generate each
> > > nesting
> > > > from Tuple and DataBag factories, append data, and next them
> manually.
> > >  For
> > > > larger unit tests, this process becomes unwieldy (hundreds of lines
> per
> > > > method, non-dynamic), and it would be much simpler to go directly
> from
> > a
> > > > String and a Schema to a DataBag Object for UDF testing (few lines of
> > > code,
> > > > easily modifiable).
> > > >
> > > > -Dan
> > > >
> > > >
> > > > On Mon, Mar 18, 2013 at 6:31 PM, Jonathan Coveney <
> [EMAIL PROTECTED]
> > > >wrote:
> > > >
> > > >> Why not just use PigStorage? This is essentially what it does. It
> > saves
> > > a
> > > >> bag as text, and then loads it again.
> > > >>
> > > >> I suppose the question becomes: why do you need to do this?
> > > >>
> > > >>
> > > >> 2013/3/18 Dan DeCapria, CivicScience <[EMAIL PROTECTED]
> >
> > > >>
> > > >> > In Java, I am trying to convert a DataBag from it's String
> > > >> representation
> > > >> > with its schema String to a valid DataBag Object:
> > > >> >
> > > >> > String databag_string = "{(apples,1024)}";
> > > >> > String schema_string = "b1:bag{t1:tuple(a:chararray,b:long)}";
> > > >> >
> > > >> > I've tried implementing something along the lines of this, but I
> > > believe
> > > >> > it's in the wrong direction, and then I get stuck:
> > > >> >
> > > >> >         String[] aliases = {"b1", "t1", "a", "b"};
> > > >> >         byte[] types = {DataType.BAG, DataType.TUPLE,
> > > >> DataType.CHARARRAY,
> > > >> > DataType.LONG};
> > > >> >         List<Schema.FieldSchema> fsList = new
> > > >> > ArrayList<Schema.FieldSchema>();
> > > >> >         for (int i = 0; i < aliases.length; i++) {
> > > >> >             fsList.add(new Schema.FieldSchema(aliases[i],
> > types[i])) ;
> > > >> >         }
> > > >> >         Schema origSchema = new Schema(fsList);
> > > >> >         ResourceSchema rsSchema = new ResourceSchema(origSchema);
> > > >> >         Schema genSchema = Schema.getPigSchema(rsSchema);
> > > >> >         ResourceSchema.ResourceFieldSchema[] rfschema > > > >> > rsSchema.getFields();
> > > >> >         ... lost here, maybe Utf8StorageConverter c = new
> > > >> > Utf8StorageConverter(); ???
> > > >> >
> > > >> >
> > > >> > An ideal process would be along the lines of:
> > > >> >
> > > >> > DataBag d = BagFactory.getInstance().newDefaultBag();