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Remove just_seeked from DBRawIterator

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This as added to make while-loops easy:

    while iter.next() {
        ...
    }

But this involves adding a layer of custom logic on top of the RocksDB
API. This is probably a bad idea given that this API is meant to closely
match the underlying iterator API in RocksDB, so this commit changes
that.

The new way to iterate is as follows:

while iter.valid() {
    ...

    iter.next();
}
master
Karl Hobley 7 years ago
parent 73d75af5c3
commit 6f1aae1997
2 changed files with 47 additions and 141 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
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  1. 113
      src/db.rs
  2. 75
      test/test_raw_iterator.rs

113
src/db.rs
Unescape View File

@ -116,26 +116,28 @@ pub struct Snapshot<'a> {
///
/// // Forwards iteration
/// iter.seek_to_first();
/// while iter.next() {
/// while iter.valid() {
/// println!("Saw {:?} {:?}", iter.key(), iter.value());
/// iter.next();
/// }
///
/// // Reverse iteration
/// iter.seek_to_last();
/// while iter.prev() {
/// while iter.valid() {
/// println!("Saw {:?} {:?}", iter.key(), iter.value());
/// iter.prev();
/// }
///
/// // Seeking
/// iter.seek(b"my key");
/// while iter.next() {
/// while iter.valid() {
/// println!("Saw {:?} {:?}", iter.key(), iter.value());
/// iter.next();
/// }
///
/// ```
pub struct DBRawIterator {
inner: *mut ffi::rocksdb_iterator_t,
just_seeked: bool,
}
@ -169,6 +171,7 @@ pub struct DBRawIterator {
pub struct DBIterator {
raw: DBRawIterator,
direction: Direction,
just_seeked: bool,
}
pub enum Direction {
@ -187,14 +190,9 @@ pub enum IteratorMode<'a> {
impl DBRawIterator {
fn new(db: &DB, readopts: &ReadOptions) -> DBRawIterator {
unsafe {
let iterator = ffi::rocksdb_create_iterator(db.inner, readopts.inner);
let mut rv = DBRawIterator {
inner: iterator,
just_seeked: false,
};
rv.seek_to_first();
rv
DBRawIterator {
inner: ffi::rocksdb_create_iterator(db.inner, readopts.inner),
}
}
}
@ -203,14 +201,9 @@ impl DBRawIterator {
readopts: &ReadOptions)
-> Result<DBRawIterator, Error> {
unsafe {
let iterator = ffi::rocksdb_create_iterator_cf(db.inner, readopts.inner, cf_handle.inner);
let mut rv = DBRawIterator {
inner: iterator,
just_seeked: false,
};
rv.seek_to_first();
Ok(rv)
Ok(DBRawIterator {
inner: ffi::rocksdb_create_iterator_cf(db.inner, readopts.inner, cf_handle.inner),
})
}
}
@ -221,8 +214,6 @@ impl DBRawIterator {
/// Seeks to the first key in the database.
///
/// You must call ``.next()`` before reading the key.
///
/// # Examples
///
/// ```rust
@ -235,16 +226,17 @@ impl DBRawIterator {
///
/// iter.seek_to_first();
///
/// while iter.next() {
/// while iter.valid() {
/// println!("{:?} {:?}", iter.key(), iter.value());
///
/// iter.next();
/// }
///
/// // Read just the first key
///
/// iter.seek_to_first();
///
/// let is_valid = iter.next();
/// if is_valid {
/// if iter.valid() {
/// println!("{:?} {:?}", iter.key(), iter.value());
/// } else {
/// // There are no keys in the database
@ -252,13 +244,10 @@ impl DBRawIterator {
/// ```
pub fn seek_to_first(&mut self) {
unsafe { ffi::rocksdb_iter_seek_to_first(self.inner); }
self.just_seeked = true;
}
/// Seeks to the last key in the database.
///
/// You must call ``.prev()`` before reading the key.
///
/// # Examples
///
/// ```rust
@ -271,16 +260,17 @@ impl DBRawIterator {
///
/// iter.seek_to_last();
///
/// while iter.prev() {
/// println!("{:?} {:?}", iter.key(), iter.value());;
/// while iter.valid() {
/// println!("{:?} {:?}", iter.key(), iter.value());
///
/// iter.prev();
/// }
///
/// // Read just the last key
///
/// iter.seek_to_last();
///
/// let is_valid = iter.prev();
/// if is_valid {
/// if iter.valid() {
/// println!("{:?} {:?}", iter.key(), iter.value());
/// } else {
/// // There are no keys in the database
@ -288,7 +278,6 @@ impl DBRawIterator {
/// ```
pub fn seek_to_last(&mut self) {
unsafe { ffi::rocksdb_iter_seek_to_last(self.inner); }
self.just_seeked = true;
}
/// Seeks to the specified key or the first key that lexicographically follows it.
@ -296,8 +285,6 @@ impl DBRawIterator {
/// This method will attempt to seek to the specified key. If that key does not exist, it will
/// find and seek to the key that lexicographically follows it instead.
///
/// Like the other seek methods, you must call ``.next()`` or ``.prev()`` before reading a key.
///
/// # Examples
///
/// ```rust
@ -310,8 +297,7 @@ impl DBRawIterator {
///
/// iter.seek(b"a");
///
/// let is_valid = iter.next();
/// if is_valid {
/// if iter.valid() {
/// println!("{:?} {:?}", iter.key(), iter.value());
/// } else {
/// // There are no keys in the database
@ -319,7 +305,6 @@ impl DBRawIterator {
/// ```
pub fn seek(&mut self, key: &[u8]) {
unsafe { ffi::rocksdb_iter_seek(self.inner, key.as_ptr() as *const c_char, key.len() as size_t); }
self.just_seeked = true;
}
/*
@ -331,7 +316,6 @@ impl DBRawIterator {
/// The difference with ``.seek()`` is that if the specified key do not exist, this method will
/// seek to key that lexicographically precedes it instead.
///
/// Like the other seek methods, you must call ``.next()`` or ``.prev()`` before reading a key.
/// # Examples
///
/// ```rust
@ -344,49 +328,28 @@ impl DBRawIterator {
///
/// iter.seek_for_prev(b"b");
///
/// let is_valid = iter.prev();
/// if is_valid {
/// if iter.valid() {
/// println!("{:?} {:?}", iter.key(), iter.value());
/// } else {
/// // There are no keys in the database
/// }
pub fn seek_for_prev(&mut self, key: &[u8]) {
unsafe { ffi::rocksdb_iter_seek_for_prev(self.inner, key.as_ptr() as *const c_char, key.len() as size_t); }
self.just_seeked = true;
}
*/
/// Seeks to the next key.
///
/// Returns true if the iterator is valid after this operation.
pub fn next(&mut self) -> bool {
// Initial call to next() after seeking should not move the iterator
// as the iterator would be positioned on the first element
// This behaviour allows the next() method to be used in a while-loop (eg. while iter.next())
if self.just_seeked {
self.just_seeked = false;
return self.valid();
} else {
unsafe { ffi::rocksdb_iter_next(self.inner); }
}
self.valid()
pub fn next(&mut self) {
unsafe { ffi::rocksdb_iter_next(self.inner); }
}
/// Seeks to the previous key.
///
/// Returns true if the iterator is valid after this operation.
pub fn prev(&mut self) -> bool {
// Initial call to prev() after seeking should not move the iterator
// as the iterator would be positioned on the first element
// This behaviour allows the prev() method to be used in a while-loop (eg. while iter.prev())
if self.just_seeked {
self.just_seeked = false;
} else {
unsafe { ffi::rocksdb_iter_prev(self.inner); }
}
self.valid()
pub fn prev(&mut self) {
unsafe { ffi::rocksdb_iter_prev(self.inner); }
}
/// Returns a slice to the internal buffer storing the current key.
@ -455,6 +418,7 @@ impl DBIterator {
let mut rv = DBIterator {
raw: DBRawIterator::new(db, readopts),
direction: Direction::Forward, // blown away by set_mode()
just_seeked: false,
};
rv.set_mode(mode);
rv
@ -468,6 +432,7 @@ impl DBIterator {
let mut rv = DBIterator {
raw: try!(DBRawIterator::new_cf(db, cf_handle, readopts)),
direction: Direction::Forward, // blown away by set_mode()
just_seeked: false,
};
rv.set_mode(mode);
Ok(rv)
@ -489,6 +454,8 @@ impl DBIterator {
self.direction = dir;
}
};
self.just_seeked = true;
}
pub fn valid(&self) -> bool {
@ -500,12 +467,18 @@ impl Iterator for DBIterator {
type Item = KVBytes;
fn next(&mut self) -> Option<KVBytes> {
let valid = match self.direction {
Direction::Forward => self.raw.next(),
Direction::Reverse => self.raw.prev(),
};
// Initial call to next() after seeking should not move the iterator
// or the first item will not be returned
if !self.just_seeked {
match self.direction {
Direction::Forward => self.raw.next(),
Direction::Reverse => self.raw.prev(),
}
} else {
self.just_seeked = false;
}
if valid {
if self.raw.valid() {
// .key() and .value() only ever return None if valid == false, which we've just cheked
Some((self.raw.key().unwrap().into_boxed_slice(), self.raw.value().unwrap().into_boxed_slice()))
} else {

75
test/test_raw_iterator.rs
Unescape View File

@ -41,32 +41,20 @@ pub fn test_forwards_iteration() {
let mut iter = db.raw_iterator();
iter.seek_to_first();
// Shouldn't be valid yet
assert_eq!(iter.valid(), false);
assert_eq!(iter.key(), None);
assert_eq!(iter.value(), None);
let valid = iter.next();
assert_eq!(valid, true);
assert_eq!(iter.valid(), true);
assert_eq!(iter.key(), Some(b"k1".to_vec()));
assert_eq!(iter.value(), Some(b"v1".to_vec()));
let valid = iter.next();
iter.next();
assert_eq!(valid, true);
assert_eq!(iter.valid(), true);
assert_eq!(iter.key(), Some(b"k2".to_vec()));
assert_eq!(iter.value(), Some(b"v2".to_vec()));
iter.next(); // k3
iter.next(); // k4
iter.next(); // invalid!
let valid = iter.next();
// Should be invalid again
assert_eq!(valid, false);
assert_eq!(iter.valid(), false);
assert_eq!(iter.key(), None);
assert_eq!(iter.value(), None);
@ -84,32 +72,20 @@ pub fn test_seek_last() {
let mut iter = db.raw_iterator();
iter.seek_to_last();
// Shouldn't be valid yet
assert_eq!(iter.valid(), false);
assert_eq!(iter.key(), None);
assert_eq!(iter.value(), None);
let valid = iter.prev();
assert_eq!(valid, true);
assert_eq!(iter.valid(), true);
assert_eq!(iter.key(), Some(b"k4".to_vec()));
assert_eq!(iter.value(), Some(b"v4".to_vec()));
let valid = iter.prev();
iter.prev();
assert_eq!(valid, true);
assert_eq!(iter.valid(), true);
assert_eq!(iter.key(), Some(b"k3".to_vec()));
assert_eq!(iter.value(), Some(b"v3".to_vec()));
iter.prev(); // k2
iter.prev(); // k1
iter.prev(); // invalid!
let valid = iter.prev();
// Should be invalid again
assert_eq!(valid, false);
assert_eq!(iter.valid(), false);
assert_eq!(iter.key(), None);
assert_eq!(iter.value(), None);
@ -127,41 +103,6 @@ pub fn test_seek() {
let mut iter = db.raw_iterator();
iter.seek(b"k2");
// Shouldn't be valid yet
assert_eq!(iter.valid(), false);
assert_eq!(iter.key(), None);
assert_eq!(iter.value(), None);
let valid = iter.next();
// Should now be valid
assert_eq!(valid, true);
assert_eq!(iter.valid(), true);
assert_eq!(iter.key(), Some(b"k2".to_vec()));
assert_eq!(iter.value(), Some(b"v2".to_vec()));
}
#[test]
pub fn test_seek_then_prev() {
let db = setup_test_db("seek_then_prev");
db.put(b"k1", b"v1").unwrap();
db.put(b"k2", b"v2").unwrap();
db.put(b"k3", b"v3").unwrap();
db.put(b"k4", b"v4").unwrap();
let mut iter = db.raw_iterator();
iter.seek(b"k2");
// Shouldn't be valid yet
assert_eq!(iter.valid(), false);
assert_eq!(iter.key(), None);
assert_eq!(iter.value(), None);
let valid = iter.prev();
// Should now be valid
assert_eq!(valid, true);
assert_eq!(iter.valid(), true);
assert_eq!(iter.key(), Some(b"k2".to_vec()));
assert_eq!(iter.value(), Some(b"v2".to_vec()));
@ -178,14 +119,6 @@ pub fn test_seek_to_nonexistant() {
let mut iter = db.raw_iterator();
iter.seek(b"k2");
// Shouldn't be valid yet
assert_eq!(iter.valid(), false);
assert_eq!(iter.key(), None);
assert_eq!(iter.value(), None);
let valid = iter.next();
assert_eq!(valid, true);
assert_eq!(iter.valid(), true);
assert_eq!(iter.key(), Some(b"k3".to_vec()));
assert_eq!(iter.value(), Some(b"v3".to_vec()));

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