Error message: "Only predicates on two join inputs are supported by join at this time"

[Google Code Exporter]

What steps will reproduce the problem?
1. Running the code in the attached file, though it requires some input 
files.

What is the expected output? What do you see instead?
I get this error message:
"java.lang.RuntimeException: Only predicates on two join inputs are 
supported by join at this time"
on the command

$Ps = join $TfDfOverDocs, $TfDfOverCol where $TfDfOverDocs.($attribute) == 
$TfDfOverCol.($attribute)
into { ($attribute): $TfDfOverCol.($attribute), term: $TfDfOverDocs.term,
        userid: $TfDfOverDocs.userid, TfDfOverCol_DF: $TfDfOverCol.DF, 
TfDfOverCol_TF: $TfDfOverCol.TF,
        TfDfOverDocs_DF: $TfDfOverDocs.DF, TfDfOverDocs_TF: 
$TfDfOverDocs.TF},

What version of the product are you using? On what operating system?
OS = Linux with kernel 2.6.9
Hadoop version = 0.20.1
JAQL version = 0.4

Please provide any additional information below.
I found the code which produce this exception:
Expr e1 = c.child(0);
Expr e2 = c.child(1);
HashSet<Var> s1 = e1.getCapturedVars();
HashSet<Var> s2 = e2.getCapturedVars();
if( s1.size() == 1 && s2.size() == 1 ) {
...  } else {
throw new RuntimeException("Only predicates on two join inputs are 
supported by join at this time");
}

But I don't understand what s1 and s2 represent.

Original issue reported on code.google.com by Avishay.Livne on 5 May 2010 at 3:47

Attachments:

• temp.txt

[Google Code Exporter]

I've realized the problem is caused by the "where" predicate (i.e., "where 
$TfDfOverDocs.($attribute) == $TfDfOverCol.($attribute)"
in which I use .($attribute) to refer to different attribute each time. If I 
replace 
($attribute) with concrete attribute name (i.e., $TfDfOverDocs.genre) then the 
code 
runs.

Is there any way to achieve this kind of generic behavior?

Original comment by Avishay.Livne on 6 May 2010 at 9:03

[Google Code Exporter]

I was able to successfully compile your query on the current trunk version (rev 
598) without the error message. I believe this was fixed a while back with 
another issue on join predicates.  Let us know if you continue to have trouble.

A computed attribute should work just fine, as long as the computation is not a 
part of the join. For example, this is not supported:

$Ps = join $attribute in ('x','y'), $TfDfOverDocs, $TfDfOverCol 
 where $TfDfOverDocs.($attribute) == $TfDfOverCol.($attribute)
  into $TfDfOverDocs;

because it computes the attribute in the join.

Original comment by [e-mail] on 10 Jul 2010 at 1:05

• Changed state: Fixed