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GetByHeight switches between linear & binary search on >=50 items

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* GetByHeight will now switch to using binary search once
we have  >=50 items.
* Feedback from @ebuchman to catch a missed spot where
we forgot about lazy sorting that the original code
assumed would always have sorted commits by height.
Added a lazy sorting routine here too.
A test as well to ensure that we always get the properly
sorted and last value.
This commit is contained in:
Emmanuel Odeke
2018-01-31 20:26:34 -07:00
parent e8d0960cef
commit 9ed296ae71
3 changed files with 197 additions and 145 deletions
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35
lite/memprovider.go
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@@ -60,12 +60,30 @@ func (m *memStoreProvider) StoreCommit(fc FullCommit) error {
// GetByHeight returns the FullCommit for height h or an error if the commit is not found.
func (m *memStoreProvider) GetByHeight(h int64) (FullCommit, error) {
m.mtx.Lock()
defer m.mtx.Unlock()
// By heuristics, GetByHeight with linearsearch is fast enough
// for about 50 keys but after that, it needs binary search.
// See https://github.com/tendermint/tendermint/pull/1043#issue-285188242
m.mtx.RLock()
n := len(m.byHeight)
m.mtx.RUnlock()
if n <= 50 {
return m.getByHeightLinearSearch(h)
}
return m.getByHeightBinarySearch(h)
}
func (m *memStoreProvider) sortByHeightIfNecessaryLocked() {
if !m.sorted {
sort.Sort(m.byHeight)
m.sorted = true
}
}
func (m *memStoreProvider) getByHeightLinearSearch(h int64) (FullCommit, error) {
m.mtx.Lock()
defer m.mtx.Unlock()
m.sortByHeightIfNecessaryLocked()
// search from highest to lowest
for i := len(m.byHeight) - 1; i >= 0; i-- {
if fc := m.byHeight[i]; fc.Height() <= h {
@@ -75,14 +93,10 @@ func (m *memStoreProvider) GetByHeight(h int64) (FullCommit, error) {
return FullCommit{}, liteErr.ErrCommitNotFound()
}
// GetByHeight returns the FullCommit for height h or an error if the commit is not found.
func (m *memStoreProvider) GetByHeightBinarySearch(h int64) (FullCommit, error) {
func (m *memStoreProvider) getByHeightBinarySearch(h int64) (FullCommit, error) {
m.mtx.Lock()
defer m.mtx.Unlock()
if !m.sorted {
sort.Sort(m.byHeight)
m.sorted = true
}
m.sortByHeightIfNecessaryLocked()
low, high := 0, len(m.byHeight)-1
var mid int
var hmid int64
@@ -126,12 +140,13 @@ func (m *memStoreProvider) GetByHash(hash []byte) (FullCommit, error) {
// LatestCommit returns the latest FullCommit or an error if no commits exist.
func (m *memStoreProvider) LatestCommit() (FullCommit, error) {
m.mtx.RLock()
defer m.mtx.RUnlock()
m.mtx.Lock()
defer m.mtx.Unlock()
l := len(m.byHeight)
if l == 0 {
return FullCommit{}, liteErr.ErrCommitNotFound()
}
m.sortByHeightIfNecessaryLocked()
return m.byHeight[l-1], nil
}