[PIG-3379] Alias reuse in nested foreach causes PIG script to fail

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.11.1
• Fix Version/s: 0.12.0
• Component/s: impl
• Hadoop Flags: Reviewed
• Assignee: Xuefu Zhang
• Reporter: Xuefu Zhang
• Created: 16/Jul/13 18:37
• Updated: 14/Oct/13 16:46
• Resolved: 23/Aug/13 21:07

Description

The following script fails:

temp.pig

Events = LOAD 'x' AS (eventTime:long, deviceId:chararray, eventName:chararray);
Events = FOREACH Events GENERATE eventTime, deviceId, eventName;
EventsPerMinute = GROUP Events BY (eventTime / 60000);
EventsPerMinute = FOREACH EventsPerMinute {
  DistinctDevices = DISTINCT Events.deviceId;
  nbDevices = SIZE(DistinctDevices);

  DistinctDevices = FILTER Events BY eventName == 'xuaHeartBeat';
  nbDevicesWatching = SIZE(DistinctDevices);

  GENERATE $0*60000 as timeStamp, nbDevices as nbDevices, nbDevicesWatching as nbDevicesWatching;
}
EventsPerMinute = FILTER EventsPerMinute BY timeStamp >= 0  AND timeStamp < 100000;
A = FOREACH EventsPerMinute GENERATE timeStamp;
describe A;

With the error:

2013-07-16 11:31:20,450 [main] ERROR org.apache.pig.tools.grunt.Grunt - ERROR 1025: 
<file /home/xzhang/Documents/temp.pig, line 14, column 37> Invalid field projection. Projected field [timeStamp] does not exist in schema: deviceId:chararray.

Using distinct alias name for the 2nd "DistinctDevices" fixes the problem. As an observation, removing the last filter statement also fixes the problem.