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Merge pull request #333 from benbjohnson/document-key-value-safety 

Document key/value safety.
master
Ben Johnson 2015-03-24 12:28:40 -06:00
parent a9651995e1 112f143631
commit 837170ea29
3 changed files with 12 additions and 0 deletions
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4
README.md
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@ -258,6 +258,10 @@ set to a key which is different than the key not existing.
Use the `Bucket.Delete()` function to delete a key from the bucket.
Please note that values returned from `Get()` are only valid while the
transaction is open. If you need to use a value outside of the transaction
then you must use `copy()` to copy it to another byte slice.
### Iterating over keys

1
bucket.go
View File

@ -252,6 +252,7 @@ func (b *Bucket) DeleteBucket(key []byte) error {
// Get retrieves the value for a key in the bucket.
// Returns a nil value if the key does not exist or if the key is a nested bucket.
// The returned value is only valid for the life of the transaction.
func (b *Bucket) Get(key []byte) []byte {
k, v, flags := b.Cursor().seek(key)

7
cursor.go
View File

@ -10,6 +10,8 @@ import (
// Cursors see nested buckets with value == nil.
// Cursors can be obtained from a transaction and are valid as long as the transaction is open.
//
// Keys and values returned from the cursor are only valid for the life of the transaction.
//
// Changing data while traversing with a cursor may cause it to be invalidated
// and return unexpected keys and/or values. You must reposition your cursor
// after mutating data.
@ -25,6 +27,7 @@ func (c *Cursor) Bucket() *Bucket {
// First moves the cursor to the first item in the bucket and returns its key and value.
// If the bucket is empty then a nil key and value are returned.
// The returned key and value are only valid for the life of the transaction.
func (c *Cursor) First() (key []byte, value []byte) {
_assert(c.bucket.tx.db != nil, "tx closed")
c.stack = c.stack[:0]
@ -41,6 +44,7 @@ func (c *Cursor) First() (key []byte, value []byte) {
// Last moves the cursor to the last item in the bucket and returns its key and value.
// If the bucket is empty then a nil key and value are returned.
// The returned key and value are only valid for the life of the transaction.
func (c *Cursor) Last() (key []byte, value []byte) {
_assert(c.bucket.tx.db != nil, "tx closed")
c.stack = c.stack[:0]
@ -58,6 +62,7 @@ func (c *Cursor) Last() (key []byte, value []byte) {
// Next moves the cursor to the next item in the bucket and returns its key and value.
// If the cursor is at the end of the bucket then a nil key and value are returned.
// The returned key and value are only valid for the life of the transaction.
func (c *Cursor) Next() (key []byte, value []byte) {
_assert(c.bucket.tx.db != nil, "tx closed")
k, v, flags := c.next()
@ -69,6 +74,7 @@ func (c *Cursor) Next() (key []byte, value []byte) {
// Prev moves the cursor to the previous item in the bucket and returns its key and value.
// If the cursor is at the beginning of the bucket then a nil key and value are returned.
// The returned key and value are only valid for the life of the transaction.
func (c *Cursor) Prev() (key []byte, value []byte) {
_assert(c.bucket.tx.db != nil, "tx closed")
@ -100,6 +106,7 @@ func (c *Cursor) Prev() (key []byte, value []byte) {
// Seek moves the cursor to a given key and returns it.
// If the key does not exist then the next key is used. If no keys
// follow, a nil key is returned.
// The returned key and value are only valid for the life of the transaction.
func (c *Cursor) Seek(seek []byte) (key []byte, value []byte) {
k, v, flags := c.seek(seek)