-RE: What is the canonicalname field in a Schema object used for?
Santhosh Srinivasan 2011-11-21, 07:17
Alan is right. Its meant to help with disambiguation when the column name is the same across relations. In Alan's example, if you had u instead of x in B, then the columns in the C (join) would be (A::u, v, B::u, y). A::v and B::y are also valid column names.
From: Alan Gates [mailto:[EMAIL PROTECTED]]
Sent: Friday, November 18, 2011 8:58 AM
To: [EMAIL PROTECTED]
Cc: Santhosh Srinivasan
Subject: Re: What is the canonicalname field in a Schema object used for?
Santosh is the best person to answer this, as he wrote that code. But, IIRC its purpose is to store the "full" name of a column after cogroups and joins. For example,
A = load 'foo' as (u, v);
B = load 'bar' as (x, y);
C = join A by u, B by x;
I believe the canonicalname will now hold A::u, etc.
On Nov 16, 2011, at 7:25 PM, Jonathan Coveney wrote:
> If you do:
> Schema s1 = Utils.getSchemaFromString(
> then it will all be -1'd out. It doesn't seem to be used anywhere, I
> was just wondering, since in other case, it will be populated properly.