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Address comments
Signed-off-by: Fabian Reinartz <freinartz@google.com>
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# WAL Disk Format
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The write ahead log operates in segments that that are numbered and sequential,
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The write ahead log operates in segments that are numbered and sequential,
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e.g. `000000`, `000001`, `000002`, etc., and are limited to 128MB by default.
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A segment is written to in pages of 32KB. Only the last page of the most recent segment
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may be partial. A WAL record is an opaque byte slice that gets split up into sub-records
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@ -17,13 +17,21 @@ Notable deviations are that the record fragment is encoded as:
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└───────────┴──────────┴────────────┴──────────────┘
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```
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The type flag has the following states:
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* `0`: rest of page will be empty
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* `1`: a full record encoded in a single fragment
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* `2`: first fragment of a record
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* `3`: middle fragment of a record
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* `4`: final fragment of a record
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## Record encoding
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The records written to the write ahead log are encoded as follows:
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### Series records
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Series records encode the labels that identifier a series and its unique ID.
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Series records encode the labels that identifies a series and its unique ID.
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```
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┌────────────────────────────────────────────┐
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@ -27,9 +27,6 @@ func ReadDir(dirpath string) ([]string, error) {
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// Rename safely renames a file.
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func Rename(from, to string) error {
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if err := os.RemoveAll(to); err != nil {
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return err
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}
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if err := os.Rename(from, to); err != nil {
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return err
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}
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@ -140,7 +140,7 @@ func OpenReadSegment(fn string) (*Segment, error) {
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// WAL is a write ahead log that stores records in segment files.
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// It must be read from start to end once before logging new data.
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// If an erroe occurs during read, the repair procedure must be called
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// If an error occurs during read, the repair procedure must be called
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// before it's safe to do further writes.
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//
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// Segments are written to in pages of 32KB, with records possibly split
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