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options.md

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Options

About options see here for detail.

Arguments Comment Type
Dir Dir represents Open the database located in which dir. string
EntryIdxMode EntryIdxMode represents using which mode to index the entries. EntryIdxMode includes three options: HintKeyValAndRAMIdxMode,HintKeyAndRAMIdxMode and HintBPTSparseIdxMode. HintKeyValAndRAMIdxMode represents ram index (key and value) mode, HintKeyAndRAMIdxMode represents ram index (only key) mode and HintBPTSparseIdxMode represents b+ tree sparse index mode. EntryIdxMode
RWMode RWMode represents the read and write mode. RWMode includes two options: FileIO and MMap. FileIO represents the read and write mode using standard I/O. And MMap represents the read and write mode using mmap. RWMode
SegmentSize NutsDB will truncate data file if the active file is larger than SegmentSize. Current version default SegmentSize is 8MB,but you can custom it. The defaultSegmentSize becomes 256MB when the version is greater than 0.8.0.

Once set, it cannot be changed. see caveats--limitations for detail.		 int64
NodeNum NodeNum represents the node number.Default NodeNum is 1. NodeNum range [1,1023] . int64
SyncEnable SyncEnable represents if call Sync() function. if SyncEnable is false, high write performance but potential data loss likely. if SyncEnable is true, slower but persistent. bool
StartFileLoadingMode StartFileLoadingMode represents when open a database which RWMode to load files. RWMode
GCWhenClose GCWhenClose represents initiative GC when calling db.Close(). Nutsdb doesn't
immediately trigger GC on db.Close() by default.		 bool
CommitBufferSize CommitBufferSize represent the size of memory preallocated for transaction. Nutsdb will preallocate memory and reducing the number of memory allocations. int64
ErrorHandler ErrorHandler handles an error that occur during transaction. ErrorHandler
LessFunc LessFunc represents func to sort keys. Nutsdb sorts keys in lexicographical order by default. LessFunc
MergeInterval MergeInterval represent the interval for automatic merges, with 0 meaning automatic merging is disabled. Default interval is 2 hours. time.Duration
MaxBatchCount MaxBatchCount represents max entries in batch. int64
MaxBatchSize MaxBatchSize represents max batch size in bytes. int64
ExpiredDeleteType ExpiredDeleteType represents the data structure used for expired deletion. TimeWheel means use the time wheel, You can use it when you need high performance or low memory usage. TimeHeap means use the time heap, You can use it when you need to delete precisely or memory usage will be high. ExpiredDeleteType

Default Options

Recommend to use the DefaultOptions. Unless you know what you're doing.

var DefaultOptions = func() Options {
    return Options{
        EntryIdxMode:      HintKeyValAndRAMIdxMode,
        SegmentSize:       defaultSegmentSize,
        NodeNum:           1,
        RWMode:            FileIO,
        SyncEnable:        true,
        CommitBufferSize:  4 * MB,
        MergeInterval:     2 * time.Hour,
        MaxBatchSize:      (15 * defaultSegmentSize / 4) / 100,
        MaxBatchCount:     (15 * defaultSegmentSize / 4) / 100 / 100,
        ExpiredDeleteType: TimeWheel,
    }
}()