How to delete previous database snapshot using regex? - powershell

Question

We are restoring a database called Cube1 as "snapshots" using below command.
$CUBE = "$CUBE-Snapshot-$dateStamp"
Restore-ASDatabase -Server $Target_Server -RestoreFile $BFile -Name $CUBE -Security:$SecurityChoice -AllowOverwrite -ErrorAction Stop
However, this is supposed to run weekly indefinitely and our server memory capacity will be diminished leading to performance issues eventually, which we don't want.
Therefore, I'd like to delete existing snapshots, so ultimate result would be something like this (1 snapshot only weekly):
I tried the following:
Import-Module sqlserver
$AnalysisServer = New-Object Microsoft.AnalysisServices.Server
$AnalysisServer.connect("$Target_Server")
$AnalysisServer.Databases["*$CUBE-Snapshot*"].Drop()
and the drop operation failed.
You cannot call a method on a null-valued expression.
When specifying manually the snapshot name:
$AnalysisServer.Databases["Cube1-Snapshot-05-30-2021-0314PM"].Drop()
The drop operation succeeds.
I suppose I need to use some sort of regex then since wildcards didn't seem to work for the name, so how do I accomplish that?

Answer 1

Using [...] to index into the .DataBases collections corresponds to the parameterized .Item[] property, which supports (a) targeting a database by numerical index or (b) by verbatim name - using patterns to match database names is not supported.
Therefore, you need to filter the database collection explicitly, which you can do with the .Where() array method, combined with member-access enumeration, which allows you to call the .Drop() method on every matching database:
$AnalysisServer.Databases.Where({ $_.Name -like "*$CUBE-Snapshot*" }).Drop()
Note: If no databases match, the above will generate a statement-terminating error; to avoid that, use a two-step approach:
$matchingDbs = $AnalysisServer.Databases.Where({ $_.Name -like "*$CUBE-Snapshot*" })
if ($matchingDbs) { $matchingDbs.Drop() }
To delete all snapshots except the most recent one, based on the naming convention shown in the question:
$matchingDbs = $AnalysisServer.Databases.Where({ $_.Name -like "*$CUBE-Snapshot*" })
if ($matchingDbs.Count -ge 2) {
($matchingDbs | Sort-Object Name -Descending | Select-Object -Skip 1).Drop()
}