Walk the path backwards when creating new directories #1057
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Not sure exactly what changed with the integration tests here but I will chase it |
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jrray
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Our original algorithm walked down from the root, creating directories as needed. This creates an operation of O(n) under all scenarios, where n is the number of path components. However, we can generally assume that these paths are going to be created once and then already exist from that point forward. This mean that for a vast majority of the operations, we are over-checking. This new system walks up from the full path, checking each entry and tracking which do not exist. Once it finds an existing parent, it walks back down creating each item. In a worst case scenario, this becomes an O(2n) operation but changes our best-case to an O(1). Eg if the path already exists, a single lstat call confirms this and nothing else needs to be done. This feels like a desirable trade-off given that most operations are likely to fall into the "already exists" bucket. Signed-off-by: Ryan Bottriell <ryan@bottriell.ca>
Signed-off-by: Ryan Bottriell <ryan@bottriell.ca>
Signed-off-by: Ryan Bottriell <ryan@bottriell.ca>
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@jrray FYI I'm not sure if you are planning to review this again since we talked about it... |
jrray
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Our original algorithm walked down from the root, creating directories as needed. This creates an operation of O(n) under all scenarios, where n is the number of path components. However, we can generally assume that these paths are going to be created once and then already exist from that point forward. This mean that for a vast majority of the operations, we are over-checking. This new system walks up from the full path, checking each entry and tracking which do not exist. Once it finds an existing parent, it walks back down creating each item. In a worst case scenario, this becomes an O(2n) operation but changes our best-case to an O(1). Eg if the path already exists, a single lstat call confirms this and nothing else needs to be done. This feels like a desirable trade-off given that most operations are likely to fall into the "already exists" bucket.