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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, 15:27
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();
> >> > d.something(databag_string, schema_string);    // ??? no idea what
> this
> >> > process could be
> >> > d.toString().equals(databag_string) == true.
> >> >
> >> > Thanks, -Dan
> >> >
> >>
> >
> >
> >
> > --
> > Dan DeCapria
> > CivicScience, Inc.
> > Senior Informatics / DM / ML / BI Specialist
> >
>
>
>
> --
> Dan DeCapria
> CivicScience, Inc.
> Senior Informatics / DM / ML / BI Specialist
>