René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Tracking FileSystem provider performance issues","articleBody":"1. The IsPathRoot() method does double check for UNC\r\nhttps://github.com/PowerShell/PowerShell/blob/281b437a65360ae869d40f3766a1f2bbba786e5e/src/System.Management.Automation/namespaces/FileSystemProvider.cs#L5026-L5047\r\nand could be replaced with more short and fast code. Proposal from @mklement0 https://github.com/PowerShell/PowerShell/issues/14497#issuecomment-751356734\r\n\r\nAlso we need to review GetFileSystemItem(string path, ref bool isContainer, bool showHidden) - there is a root check and maybe a bug (no UNC share check)\r\nhttps://github.com/PowerShell/PowerShell/blob/281b437a65360ae869d40f3766a1f2bbba786e5e/src/System.Management.Automation/namespaces/FileSystemProvider.cs#L1426-L1430\r\n\r\n2. PR #14469 Reduce aggressive correcting casing of file system paths\r\nOn Windows we do case normalizations even if results are not used.\r\n\r\n3. No need to allocate FileInfo and extra strings in IsSameWindowsVolume():\r\nhttps://github.com/PowerShell/PowerShell/blob/281b437a65360ae869d40f3766a1f2bbba786e5e/src/System.Management.Automation/namespaces/FileSystemProvider.cs#L6141-L6147\r\nWe can use `GetDirectoryName(ReadOnlySpan\u003cchar\u003e path)`. Also we should use Ordinal comparison.\r\n\r\n4. EnsureDriveIsRooted() method does extra path.IndexOf(':') - we can simply check last char\r\nhttps://github.com/PowerShell/PowerShell/blob/281b437a65360ae869d40f3766a1f2bbba786e5e/src/System.Management.Automation/namespaces/FileSystemProvider.cs#L5709-L5727\r\n\r\n5. We need to review semantic of IsValidPath() method. If it is exactly about path validity the method could be simplified but we need to measure a performance. In common case it is impossible to validate path by parsing but only by opening.\r\nhttps://github.com/PowerShell/PowerShell/blob/281b437a65360ae869d40f3766a1f2bbba786e5e/src/System.Management.Automation/namespaces/FileSystemProvider.cs#L1192-L1246\r\n\r\n6. Statistic shows:\r\n```powershell\r\ndir -Recurse 'C:\\Program Files (x86)\\' | Select -ExpandProperty Mode | Sort-Object  | Group-Object -NoElement\r\n\r\nCount Name\r\n----- ----\r\n    1 -----\r\n    3 --r--\r\n44263 -a---\r\n    6 -ar--\r\n 8136 d----\r\n    3 d---s\r\n    2 d-r--\r\n 1044 la---\r\n```\r\nand we could add \"la---\" as a static element in\r\nhttps://github.com/PowerShell/PowerShell/blob/281b437a65360ae869d40f3766a1f2bbba786e5e/src/System.Management.Automation/namespaces/FileSystemProvider.cs#L2024-L2040\r\n```c#\r\n                if (!isLink)\r\n                {\r\n                    // special casing for the common cases - no allocations\r\n                    switch (fileAttributes)\r\n                    {\r\n                        case FileAttributes.Archive:\r\n                            return \"-a---\";\r\n                        case FileAttributes.Directory:\r\n                            return \"d----\";\r\n                        case FileAttributes.Normal:\r\n                            return \"-----\";\r\n                        case FileAttributes.Directory | FileAttributes.ReadOnly:\r\n                            return \"d-r--\";\r\n                        case FileAttributes.Archive | FileAttributes.ReadOnly:\r\n                            return \"-ar--\";\r\n                    }\r\n                }\r\n                else if (fileAttributes == FileAttributes.ReadOnly)\r\n                {\r\n                    return \"la---\";\r\n                }\r\n\r\n           ...\r\n```\r\n\r\n7. Remove double check ItemExists();\r\nhttps://github.com/PowerShell/PowerShell/blob/281b437a65360ae869d40f3766a1f2bbba786e5e/src/System.Management.Automation/namespaces/FileSystemProvider.cs#L6105-L6112","author":{"url":"https://github.com/iSazonov","@type":"Person","name":"iSazonov"},"datePublished":"2020-12-25T07:33:59.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":9},"url":"https://github.com/14497/PowerShell/issues/14497"}