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110 lines
2.2 KiB
110 lines
2.2 KiB
package remote
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import (
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"context"
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"sync"
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)
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const (
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iteratorOnce = 300
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)
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type RemoteIterator struct {
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db *RemoteDatabase
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lock sync.Mutex
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limit []byte
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start []byte
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err error
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end bool
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pos int
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keys, values [][]byte
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currentKey, currentValue []byte
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}
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func newRemoteIterator(db *RemoteDatabase, start, limit []byte) *RemoteIterator {
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return &RemoteIterator{
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db: db,
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start: start,
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limit: limit,
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}
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}
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// Next moves the iterator to the next key/value pair. It returns whether the
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// iterator is exhausted.
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func (i *RemoteIterator) Next() bool {
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if i.end {
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return false
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}
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if i.keys == nil {
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if next := i.scanNext(); !next {
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return false
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}
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}
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i.currentKey = i.keys[i.pos]
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i.currentValue = i.values[i.pos]
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i.pos++
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if i.pos >= len(i.keys) {
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i.scanNext()
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}
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return true
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}
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// scanNext real scan from tikv, and cache it
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func (i *RemoteIterator) scanNext() bool {
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keys, values, err := i.db.client.Scan(context.Background(), i.start, i.limit, iteratorOnce)
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if err != nil {
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i.err = err
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i.end = true
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return false
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}
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if len(keys) == 0 {
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i.end = true
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return false
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} else {
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i.start = append(keys[len(keys)-1], 0)
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}
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i.pos = 0
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i.keys = keys
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i.values = values
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return true
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}
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// Error returns any accumulated error. Exhausting all the key/value pairs
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// is not considered to be an error.
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func (i *RemoteIterator) Error() error {
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return i.err
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}
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// Key returns the key of the current key/value pair, or nil if done. The caller
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// should not modify the contents of the returned slice, and its contents may
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// change on the next call to Next.
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func (i *RemoteIterator) Key() []byte {
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return i.currentKey
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}
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// Value returns the value of the current key/value pair, or nil if done. The
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// caller should not modify the contents of the returned slice, and its contents
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// may change on the next call to Next.
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func (i *RemoteIterator) Value() []byte {
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return i.currentValue
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}
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// Release releases associated resources. Release should always succeed and can
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// be called multiple times without causing error.
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func (i *RemoteIterator) Release() {
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i.db = nil
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i.end = true
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i.keys = nil
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i.values = nil
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i.currentKey = nil
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i.currentValue = nil
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}
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