I have two Scala lists with different columns, but when I compare them using .diff(), I get unexpected results.

val TempPmTableColumns: Seq[String] = List("COLLECTTIME", "DATE", "TIME", "HOUR", "DAY", "WEEK", "MONTH", "NODE", "NEUSERNAME", "SUSPECTFLAG", "CELLID", "NODE_PM", "CELLID_TYPE", "ASLDUR", "CHOVERS", "LBUSDUR", "LINHNO", "LOCINHDUR", "NMSURE", "NMSUTR", "NNAREC", "NORTRO", "NSIFSRE", "NSIFTR", "NSLALPRFL", "NSUERR", "REMINHDUR", "RINHNO", "SYS7IND", "UNAVAILDUR", "UNAVRBLDUR", "UNAVSLFDUR", "COLLINT", "FILE_REVISION", "JOBTIME")
    
val finalPmTableColumns: Seq[String]= List("COLLECTTIME", "CELLID", "NODE", "SUSPECTFLAG", "NEUSERNAME", "NETWORK", "CITY", "REGION", "PERIOD", "DATE", "TIME", "HOUR", "DAY", "WEEK", "MONTH", "NODE_PM", "CELLID_TYPE", "ASLDUR", "CHOVERS", "LBUSDUR", "LINHNO", "LOCINHDUR", "NMSURE", "NMSUTR", "NNAREC", "NORTRO", "NSIFSRE", "NSIFTR", "NSLALPRFL", "NSUERR", "REMINHDUR", "RINHNO", "SYS7IND", "UNAVAILDUR", "UNAVRBLDUR", "UNAVSLFDUR", "COLLINT", "FILE_REVISION", "JOBTIME", "NODE_VALUE")
    
println(TempPmTableColumns)
println(finalPmTableColumns)
    
var ColumnDifferenceleft = TempPmTableColumns.diff(finalPmTableColumns)
println(ColumnDifferenceleft)
    
var ColumnDifferenceRight = finalPmTableColumns.diff(TempPmTableColumns)
println(ColumnDifferenceRight)

Output:-
List(COLLECTTIME, DATE, TIME, HOUR, DAY, WEEK, MONTH, NODE, NEUSERNAME, SUSPECTFLAG, CELLID, NODE_PM, CELLID_TYPE, ASLDUR, CHOVERS, LBUSDUR, LINHNO, LOCINHDUR, NMSURE, NMSUTR, NNAREC, NORTRO, NSIFSRE, NSIFTR, NSLALPRFL, NSUERR, REMINHDUR, RINHNO, SYS7IND, UNAVAILDUR, UNAVRBLDUR, UNAVSLFDUR, COLLINT, FILE_REVISION, JOBTIME)

List(COLLECTTIME, CELLID, NODE, SUSPECTFLAG, NEUSERNAME, NETWORK, CITY, REGION, PERIOD, DATE, TIME, HOUR, DAY, WEEK, MONTH, NODE_PM, CELLID_TYPE, ASLDUR, CHOVERS, LBUSDUR, LINHNO, LOCINHDUR, NMSURE, NMSUTR, NNAREC, NORTRO, NSIFSRE, NSIFTR, NSLALPRFL, NSUERR, REMINHDUR, RINHNO, SYS7IND, UNAVAILDUR, UNAVRBLDUR, UNAVSLFDUR, COLLINT, FILE_REVISION, JOBTIME, NODE_VALUE)

List()

List(NETWORK, CITY, REGION, PERIOD, NODE_VALUE)

I have two Scala lists with different columns, but when I compare them using .diff(), I get unexpected results.

val TempPmTableColumns: Seq[String] = List("COLLECTTIME", "DATE", "TIME", "HOUR", "DAY", "WEEK", "MONTH", "NODE", "NEUSERNAME", "SUSPECTFLAG", "CELLID", "NODE_PM", "CELLID_TYPE", "ASLDUR", "CHOVERS", "LBUSDUR", "LINHNO", "LOCINHDUR", "NMSURE", "NMSUTR", "NNAREC", "NORTRO", "NSIFSRE", "NSIFTR", "NSLALPRFL", "NSUERR", "REMINHDUR", "RINHNO", "SYS7IND", "UNAVAILDUR", "UNAVRBLDUR", "UNAVSLFDUR", "COLLINT", "FILE_REVISION", "JOBTIME")
    
val finalPmTableColumns: Seq[String]= List("COLLECTTIME", "CELLID", "NODE", "SUSPECTFLAG", "NEUSERNAME", "NETWORK", "CITY", "REGION", "PERIOD", "DATE", "TIME", "HOUR", "DAY", "WEEK", "MONTH", "NODE_PM", "CELLID_TYPE", "ASLDUR", "CHOVERS", "LBUSDUR", "LINHNO", "LOCINHDUR", "NMSURE", "NMSUTR", "NNAREC", "NORTRO", "NSIFSRE", "NSIFTR", "NSLALPRFL", "NSUERR", "REMINHDUR", "RINHNO", "SYS7IND", "UNAVAILDUR", "UNAVRBLDUR", "UNAVSLFDUR", "COLLINT", "FILE_REVISION", "JOBTIME", "NODE_VALUE")
    
println(TempPmTableColumns)
println(finalPmTableColumns)
    
var ColumnDifferenceleft = TempPmTableColumns.diff(finalPmTableColumns)
println(ColumnDifferenceleft)
    
var ColumnDifferenceRight = finalPmTableColumns.diff(TempPmTableColumns)
println(ColumnDifferenceRight)

Output:-
List(COLLECTTIME, DATE, TIME, HOUR, DAY, WEEK, MONTH, NODE, NEUSERNAME, SUSPECTFLAG, CELLID, NODE_PM, CELLID_TYPE, ASLDUR, CHOVERS, LBUSDUR, LINHNO, LOCINHDUR, NMSURE, NMSUTR, NNAREC, NORTRO, NSIFSRE, NSIFTR, NSLALPRFL, NSUERR, REMINHDUR, RINHNO, SYS7IND, UNAVAILDUR, UNAVRBLDUR, UNAVSLFDUR, COLLINT, FILE_REVISION, JOBTIME)

List(COLLECTTIME, CELLID, NODE, SUSPECTFLAG, NEUSERNAME, NETWORK, CITY, REGION, PERIOD, DATE, TIME, HOUR, DAY, WEEK, MONTH, NODE_PM, CELLID_TYPE, ASLDUR, CHOVERS, LBUSDUR, LINHNO, LOCINHDUR, NMSURE, NMSUTR, NNAREC, NORTRO, NSIFSRE, NSIFTR, NSLALPRFL, NSUERR, REMINHDUR, RINHNO, SYS7IND, UNAVAILDUR, UNAVRBLDUR, UNAVSLFDUR, COLLINT, FILE_REVISION, JOBTIME, NODE_VALUE)

List()

List(NETWORK, CITY, REGION, PERIOD, NODE_VALUE)

• scala

• What result do you expect? – talex Commented Apr 1 at 11:15
• 1 Maybe rather than List, you want to use Set and then do (s1 union s2) diff (s1 intersect s2) – Luis Miguel Mejía Suárez Commented Apr 1 at 13:22

1 Answer 1

finalPmTableColumns contains all items in TempPmTableColumns, plus the following: "NETWORK", "CITY", "REGION", "PERIOD", "NODE_VALUE".

listA.diff(listB) returns listA minus all items in listB. Items in listB that are not in listA are ignored. So if listB contains all items in listA, then listA.diff(listB) will return an empty list, regardless of whether listB has some other items. diff is not commutative.