[PIG-3941] Piggybank's Over UDF returns an output schema with named fields

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 0.13.0
• Component/s: piggybank
• Labels: piggybank schema udf window
• Patch Info: Patch Available
• Release Note: Passing a 'name:type' string to the constructor for Piggybank's Over UDF sets the name and type of the result in the output schema.
• Assignee: Flip Kromer
• Reporter: Flip Kromer
• Created: 16/May/14 16:08
• Updated: 07/Jul/14 18:08
• Resolved: 19/May/14 21:55

Description

With attached patch, if Over is constructed with a colon-delimited string like 'bob:int', the first part is used to set the return field's name and the second part its type. Otherwise, if a type is given the name of the return field is set to 'result'.

cities = LOAD 'us_city_pops.tsv' AS (city:chararray, state:chararray, pop:int);
DEFINE IOver                  org.apache.pig.piggybank.evaluation.Over('state_rk:int');

ranked = FOREACH(GROUP cities BY state) {
  c_ord = ORDER cities BY pop DESC;
  GENERATE FLATTEN(Stitch(c_ord,
    IOver(c_ord, 'rank', -1, -1, 2))); -- beginning (-1) to end (-1) on third field (2)
};
DESCRIBE ranked;
-- ranked: {stitched::city: chararray,stitched::state: chararray,stitched::pop: int,stitched::state_rk: int}
DUMP ranked;
-- ...
-- (Nashville,Tennessee,609644,2)
-- (Houston,Texas,2145146,1)
-- (San Antonio,Texas,1359758,2)
-- (Dallas,Texas,1223229,3)
-- (Austin,Texas,820611,4)
-- ...