Sort an array containing a lot of dates quickly - powershell

Question

I have a huge array which contains dates. The date has the following form: tt.mm.yyyy. I know how to sort the array with Sort-Object, but the sorting takes a lot of time. I found another way of sorting arrays, but it doesn't work as expected.
My former code to sort the array was like this.
$data | Sort-Object { [System.DateTime]::ParseExact($_, "dd.MM.yyyy", $null) }
But as I siad before: this way of sorting is too slow. The Sort() method from System.Array seems to be much faster.
[Array]::Sort([array]$array)
This code sorts an array containing strings much faster than Sort-Object. Is there a way how I can change the above sorting method like the Sort-Object method?

Answer 1

The .NET method will work for dates if you make sure that the array is of type DateTime.
Meaning you should use
[DateTime[]]$dateArray
instead of
[Array]$dateArray
when you create it. Then you can use
[Array]::Sort($dateArray)
to perform the sort it self...

Answer 2

Your input data are date strings with a date format that doesn't allow sorting in "date" order. You must convert the strings either to actual dates
Get-Date $_
[DateTime]::ParseExact($_, "dd.MM.yyyy", $null)
or change the format of the string dates to ISO format, which does allow sorting in date order.
'{2}-{1}-{0}' -f ($_ -split '.')
'{0}-{1}-{2}' -f $_.Substring(6,4), $_.Substring(3,2), $_.Substring(0,2)
$_ -replace '(\d+)\.(\d+).(\d+)', '$3-$2-$1'
At some point you must do one of these conversions, either when creating the data or when sorting.
I ran some tests WRT performance of each conversion, and string transformation using the Substring() method seems to be the fastest way:
PS C:\> $dates = 1..10000 | % {
>> $day = Get-Random -Min 1 -Max 28
>> $month = (Get-Random -Min 1 -Max 12
>> $year = Get-Random -Min 1900 -Max 2014
>> '{0:d2}.{1:d2}.{2}' -f $day, $month, $year
>> }
>>
PS C:\> Measure-Command { $dates | sort {Get-Date $_} }
Days : 0
Hours : 0
Minutes : 0
Seconds : 1
Milliseconds : 520
Ticks : 15200396
TotalDays : 1,75930509259259E-05
TotalHours : 0,000422233222222222
TotalMinutes : 0,0253339933333333
TotalSeconds : 1,5200396
TotalMilliseconds : 1520,0396
PS C:\> Measure-Command { $dates | sort {'{2}-{1}-{0}' -f ($_ -split '.')} }
Days : 0
Hours : 0
Minutes : 0
Seconds : 0
Milliseconds : 413
Ticks : 4139027
TotalDays : 4,79054050925926E-06
TotalHours : 0,000114972972222222
TotalMinutes : 0,00689837833333333
TotalSeconds : 0,4139027
TotalMilliseconds : 413,9027
PS C:\> Measure-Command { $dates | sort {$_ -replace '(\d+)\.(\d+).(\d+)', '$3-$2-$1'} }
Days : 0
Hours : 0
Minutes : 0
Seconds : 0
Milliseconds : 348
Ticks : 3488962
TotalDays : 4,03815046296296E-06
TotalHours : 9,69156111111111E-05
TotalMinutes : 0,00581493666666667
TotalSeconds : 0,3488962
TotalMilliseconds : 348,8962
PS C:\> Measure-Command { $dates | sort {[DateTime]::ParseExact($_, "dd.MM.yyyy", $null)} }
Days : 0
Hours : 0
Minutes : 0
Seconds : 0
Milliseconds : 340
Ticks : 3408966
TotalDays : 3,9455625E-06
TotalHours : 9,46935E-05
TotalMinutes : 0,00568161
TotalSeconds : 0,3408966
TotalMilliseconds : 340,8966
PS C:\> Measure-Command { $dates | sort {'{0}-{1}-{2}' -f $_.Substring(6,4), $_.Substring(3,2), $_.Substring(0,2)} }
Days : 0
Hours : 0
Minutes : 0
Seconds : 0
Milliseconds : 292
Ticks : 2926835
TotalDays : 3,38754050925926E-06
TotalHours : 8,13009722222222E-05
TotalMinutes : 0,00487805833333333
TotalSeconds : 0,2926835
TotalMilliseconds : 292,6835