[jira] Created: (PIG-1231) DataBagIterator.hasNext() should be idempotent

[Daniel Dai (JIRA)]

DataBagIterator.hasNext() should be idempotent
----------------------------------------------

                 Key: PIG-1231
                 URL: https://issues.apache.org/jira/browse/PIG-1231
             Project: Pig
          Issue Type: Bug
          Components: impl
    Affects Versions: 0.6.0
            Reporter: Daniel Dai
            Assignee: Daniel Dai
             Fix For: 0.6.0


Current implementation of DataBagIterator.hasNext() will actually fetch the 
next tuple every time. So if we call hasNext() consecutively, more than 1 
tuples will be fetched. This is confusing cuz the name hasNext() implies that 
it is idempotent. In BagFormat, we do misuse DataBagIterator.hasNext() because 
of this, which leads to some mysterious errors. Here is one error we saw:

Caused by: java.io.IOException: Stream closed
        at 
java.io.BufferedInputStream.getBufIfOpen(BufferedInputStream.java:145)
        at java.io.BufferedInputStream.fill(BufferedInputStream.java:189)
        at java.io.BufferedInputStream.read(BufferedInputStream.java:237)
        at java.io.DataInputStream.readByte(DataInputStream.java:248)
        at org.apache.pig.data.DefaultTuple.readFields(DefaultTuple.java:278)
        at 
org.apache.pig.data.DefaultDataBag$DefaultDataBagIterator.readFromFile(DefaultDataBag.java:237)
        ... 20 more

This happens because: we call hasNext(), which reach EOF and we close the file. 
Then we call hasNext() again in the assumption that it is idempotent. However, 
the stream is closed so we get this error message.

This fix will go to DefaultDataBagIterator, DistinctDataBagIterator, 
CachedBagIterator, SortedDataBagIterator. 

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.