Computed expression from columns of joined tables missing in results

[kristinriebe]

Original Query

select abs(f1.x-f2.x) as xdist, f1.fofId, f2.fofId from Bolshoi.FOF as f1, Bolshoi.FOF as f2 where f1.snapnum=416 and f2.snapnum=416 and f1.mass > 5.e13 and f2.mass > 5.e13
Limit 10

Problem
xdist is not calculated and not written to results. All necessary columns (f1.x`, f2.x) are selected, but during the join, the expression is forgotten.
This happens, as soon as I use data from the two joined tables. If I calculated a value based on two columns from the same table (f1.x+f1.y or so), everything works fine.

If I add the computed expression in the where-clause: and abs(f1.x-f2.x) < 0.5
then it will be correctly taken into account in the query plan for filtering the results, but again the value won't be given in the results-table.

Goal
This is needed for being able to match halos from different catalogues based on distance or other properties.

Query Plan

-- CALL paquExec('SELECT `f2`.`x` AS `f2.x`,`f2`.`fofId` AS `f2.fofId`,`f2`.`snapnum` AS `f2.snapnum`,`f2`.`mass` AS `f2.mass` FROM Bolshoi.FOF AS `f2` WHERE ( `f2`.`snapnum` = 416 ) and ( `f2`.`mass` > 5.e13 ) ', 'aggregation_tmp_17895463')
-- CALL paquExec('SELECT `f1`.`fofId` AS `f1.fofId`,`f2`.`f2.fofId` AS `f2.fofId` FROM Bolshoi.FOF AS `f1` JOIN ( SELECT `f2.x`,`f2.fofId`,`f2.snapnum`,`f2.mass` FROM `aggregation_tmp_17895463` ) AS `f2` WHERE ( `f1`.`snapnum` = 416 ) and ( `f1`.`mass` > 5.e13 ) LIMIT 0,10', 'aggregation_tmp_35129861')
-- CALL paquDropTmp('aggregation_tmp_17895463')
-- USE spider_tmp_shard-- SET @i=0-- CREATE TABLE cosmosim_user_kristin.`user--calcissue2` ENGINE=MyISAM SELECT @i:=@i+1 AS `row_id`, `f1.fofId`,`f2.fofId` FROM `aggregation_tmp_35129861` LIMIT 0,10
-- CALL paquDropTmp('aggregation_tmp_35129861')

Desired Query Plan

-- CALL paquExec('SELECT `f2`.`x` AS `f2.x`,`f2`.`fofId` AS `f2.fofId`,`f2`.`snapnum` AS `f2.snapnum`,`f2`.`mass` AS `f2.mass` FROM Bolshoi.FOF AS `f2` WHERE ( `f2`.`snapnum` = 416 ) and ( `f2`.`mass` > 5.e13 ) ', 'aggregation_tmp_17895463')
-- CALL paquExec('SELECT abs( `f1`.`x` - `f2`.`f2.x` ) AS `xdist`,`f1`.`fofId` AS `f1.fofId`,`f2`.`f2.fofId` AS `f2.fofId` FROM Bolshoi.FOF AS `f1` JOIN ( SELECT `f2.x`,`f2.fofId`,`f2.snapnum`,`f2.mass` FROM `aggregation_tmp_17895463` ) AS `f2` WHERE ( `f1`.`snapnum` = 416 ) and ( `f1`.`mass` > 5.e13 ) LIMIT 0,10', 'aggregation_tmp_35129861')
-- CALL paquDropTmp('aggregation_tmp_17895463')
-- USE spider_tmp_shard-- SET @i=0-- CREATE TABLE cosmosim_user_kristin.`user--calcissue2` ENGINE=MyISAM SELECT @i:=@i+1 AS `row_id`, `f1.fofId`,`f2.fofId` FROM `aggregation_tmp_35129861` LIMIT 0,10
-- CALL paquDropTmp('aggregation_tmp_35129861')