ClearReportCache

UPDATE SN
   SET SN.PermanentRefcount = SN.PermanentRefcount - 1
FROM
   [ReportServerTempDB].dbo.SnapshotData AS SN
   INNER JOIN [ReportServerTempDB].dbo.ExecutionCache AS EC ON SN.SnapshotDataID = EC.SnapshotDataID
   INNER JOIN Catalog AS C ON EC.ReportID = C.ItemID
WHERE C.Path LIKE '%%'

DELETE EC
FROM
   [ReportServerTempDB].dbo.ExecutionCache AS EC
   INNER JOIN Catalog ON EC.ReportID = Catalog.ItemID
WHERE Catalog.Path LIKE '%%'