Documentation
¶
Overview ¶
Package iterator provides interface and implementation to traverse over contents of a database.
Index ¶
Constants ¶
This section is empty.
Variables ¶
var (
ErrIterReleased = errors.New("leveldb/iterator: iterator released")
)
Functions ¶
This section is empty.
Types ¶
type Array ¶
type Array interface {
BasicArray
// Index returns key/value pair with index of i.
Index(i int) (key, value []byte)
}
Array is the interface that wraps BasicArray and basic Index method.
type ArrayIndexer ¶
type ArrayIndexer interface {
BasicArray
// Get returns a new data iterator with index of i.
Get(i int) Iterator
}
Array is the interface that wraps BasicArray and basic Get method.
type BasicArray ¶
type BasicArray interface {
// Len returns length of the array.
Len() int
// Search finds smallest index that point to a key that is greater
// than or equal to the given key.
Search(key []byte) int
}
BasicArray is the interface that wraps basic Len and Search method.
type CommonIterator ¶
type CommonIterator interface {
IteratorSeeker
// util.Releaser is the interface that wraps basic Release method.
// When called Release will releases any resources associated with the
// iterator.
util.Releaser
// util.ReleaseSetter is the interface that wraps the basic SetReleaser
// method.
util.ReleaseSetter
// TODO: Remove this when ready.
Valid() bool
// Error returns any accumulated error. Exhausting all the key/value pairs
// is not considered to be an error.
Error() error
}
CommonIterator is the interface that wraps common interator methods.
type ErrorCallbackSetter ¶
type ErrorCallbackSetter interface {
// SetErrorCallback allows set an error callback of the coresponding
// iterator. Use nil to clear the callback.
SetErrorCallback(f func(err error))
}
ErrorCallbackSetter is the interface that wraps basic SetErrorCallback method.
ErrorCallbackSetter implemented by indexed and merged iterator.
type Iterator ¶
type Iterator interface {
CommonIterator
// Key returns the key of the current key/value pair, or nil if done.
// The caller should not modify the contents of the returned slice, and
// its contents may change on the next call to any 'seeks method'.
Key() []byte
// Value returns the key of the current key/value pair, or nil if done.
// The caller should not modify the contents of the returned slice, and
// its contents may change on the next call to any 'seeks method'.
Value() []byte
}
Iterator iterates over a DB's key/value pairs in key order.
When encouter an error any 'seeks method' will return false and will yield no key/value pairs. The error can be queried by calling the Error method. Calling Release is still necessary.
An iterator must be released after use, but it is not necessary to read an iterator until exhaustion. Also, an iterator is not necessarily goroutine-safe, but it is safe to use multiple iterators concurrently, with each in a dedicated goroutine.
func NewArrayIterator ¶
NewArrayIterator returns an iterator from the given array.
func NewEmptyIterator ¶
NewEmptyIterator creates an empty iterator. The err parameter can be nil, but if not nil the given err will be returned by Error method.
func NewIndexedIterator ¶
func NewIndexedIterator(index IteratorIndexer, strict, strictGet bool) Iterator
NewIndexedIterator returns an indexed iterator. An index is iterator that returns another iterator, a data iterator. A data iterator is the iterator that contains actual key/value pairs.
If strict is true then error yield by data iterator will halt the indexed iterator, on contrary if strict is false then the indexed iterator will ignore those error and move on to the next index. If strictGet is true and index.Get() yield an 'error iterator' then the indexed iterator will be halted. An 'error iterator' is iterator which its Error() method always return non-nil even before any 'seeks method' is called.
func NewMergedIterator ¶
NewMergedIterator returns an iterator that merges its input. Walking the resultant iterator will return all key/value pairs of all input iterators in strictly increasing key order, as defined by cmp. The input's key ranges may overlap, but there are assumed to be no duplicate keys: if iters[i] contains a key k then iters[j] will not contain that key k. None of the iters may be nil.
If strict is true then error yield by any iterators will halt the merged iterator, on contrary if strict is false then the merged iterator will ignore those error and move on to the next iterator.
type IteratorIndexer ¶
type IteratorIndexer interface {
CommonIterator
// Get returns a new data iterator for the current position, or nil if
// done.
Get() Iterator
}
IteratorIndexer is the interface that wraps CommonIterator and basic Get method. IteratorIndexer provides index for indexed iterator.
func NewArrayIndexer ¶
func NewArrayIndexer(array ArrayIndexer) IteratorIndexer
NewArrayIndexer returns an index iterator from the given array.
type IteratorSeeker ¶
type IteratorSeeker interface {
// First moves the iterator to the first key/value pair. If the iterator
// only contains one key/value pair then First and Last whould moves
// to the same key/value pair.
// It returns whether such pair exist.
First() bool
// Last moves the iterator to the last key/value pair. If the iterator
// only contains one key/value pair then First and Last whould moves
// to the same key/value pair.
// It returns whether such pair exist.
Last() bool
// Seek moves the iterator to the first key/value pair whose key is greater
// than or equal to the given key.
// It returns whether such pair exist.
//
// It is safe to modify the contents of the argument after Seek returns.
Seek(key []byte) bool
// Next moves the iterator to the next key/value pair.
// It returns whether the iterator is exhausted.
Next() bool
// Prev moves the iterator to the previous key/value pair.
// It returns whether the iterator is exhausted.
Prev() bool
}
IteratorSeeker is the interface that wraps the 'seeks method'.
Source Files