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fd3cbab6ee
Potentially fixes the database corruption seen on #1603 |
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btree.go | ||
LICENSE | ||
README.md |
btree
An efficient B-tree implementation in Go.
Features
Copy()
method with copy-on-write support.- Fast bulk loading for pre-ordered data using the
Load()
method. - All operations are thread-safe.
- Path hinting optimization for operations with nearby keys.
Installing
To start using btree, install Go and run go get
:
$ go get -u github.com/tidwall/btree
Usage
package main
import (
"fmt"
"github.com/tidwall/btree"
)
type Item struct {
, Val string
Key}
// byKeys is a comparison function that compares item keys and returns true
// when a is less than b.
func byKeys(a, b interface{}) bool {
, i2 := a.(*Item), b.(*Item)
i1return i1.Key < i2.Key
}
// byVals is a comparison function that compares item values and returns true
// when a is less than b.
func byVals(a, b interface{}) bool {
, i2 := a.(*Item), b.(*Item)
i1if i1.Val < i2.Val {
return true
}
if i1.Val > i2.Val {
return false
}
// Both vals are equal so we should fall though
// and let the key comparison take over.
return byKeys(a, b)
}
func main() {
// Create a tree for keys and a tree for values.
// The "keys" tree will be sorted on the Keys field.
// The "values" tree will be sorted on the Values field.
:= btree.New(byKeys)
keys := btree.New(byVals)
vals
// Create some items.
:= []*Item{
users &Item{Key: "user:1", Val: "Jane"},
&Item{Key: "user:2", Val: "Andy"},
&Item{Key: "user:3", Val: "Steve"},
&Item{Key: "user:4", Val: "Andrea"},
&Item{Key: "user:5", Val: "Janet"},
&Item{Key: "user:6", Val: "Andy"},
}
// Insert each user into both trees
for _, user := range users {
.Set(user)
keys.Set(user)
vals}
// Iterate over each user in the key tree
.Ascend(nil, func(item interface{}) bool {
keys:= item.(*Item)
kvi .Printf("%s %s\n", kvi.Key, kvi.Val)
fmtreturn true
})
.Printf("\n")
fmt// Iterate over each user in the val tree
.Ascend(nil, func(item interface{}) bool {
vals:= item.(*Item)
kvi .Printf("%s %s\n", kvi.Key, kvi.Val)
fmtreturn true
})
// Output:
// user:1 Jane
// user:2 Andy
// user:3 Steve
// user:4 Andrea
// user:5 Janet
// user:6 Andy
//
// user:4 Andrea
// user:2 Andy
// user:6 Andy
// user:1 Jane
// user:5 Janet
// user:3 Steve
}
Operations
Basic
Len() # return the number of items in the btree
Set(item) # insert or replace an existing item
Get(item) # get an existing item
Delete(item) # delete an item
Iteration
Ascend(pivot, iter) # scan items in ascending order starting at pivot.
Descend(pivot, iter) # scan items in descending order starting at pivot.
Queues
Min() # return the first item in the btree
Max() # return the last item in the btree
PopMin() # remove and return the first item in the btree
PopMax() # remove and return the last item in the btree
Bulk loading
Load(item) # load presorted items into tree
Path hints
SetHint(item, *hint) # insert or replace an existing item
GetHint(item, *hint) # get an existing item
DeleteHint(item, *hint) # delete an item
Performance
This implementation was designed with performance in mind.
The following benchmarks were run on my 2019 Macbook Pro (2.4 GHz 8-Core Intel Core i9) using Go 1.15.3. The items are simple 8-byte ints.
google
: The google/btree packagetidwall
: The tidwall/btree packagego-arr
: Just a simple Go array
** sequential set **
google: set-seq 1,000,000 ops in 160ms, 6,262,097/sec, 159 ns/op, 31.0 MB, 32 bytes/op
tidwall: set-seq 1,000,000 ops in 142ms, 7,020,721/sec, 142 ns/op, 36.6 MB, 38 bytes/op
tidwall: set-seq-hint 1,000,000 ops in 87ms, 11,503,315/sec, 86 ns/op, 36.6 MB, 38 bytes/op
tidwall: load-seq 1,000,000 ops in 37ms, 27,177,242/sec, 36 ns/op, 36.6 MB, 38 bytes/op
go-arr: append 1,000,000 ops in 49ms, 20,574,760/sec, 48 ns/op
** random set **
google: set-rand 1,000,000 ops in 606ms, 1,649,921/sec, 606 ns/op, 21.5 MB, 22 bytes/op
tidwall: set-rand 1,000,000 ops in 543ms, 1,841,590/sec, 543 ns/op, 26.7 MB, 27 bytes/op
tidwall: set-rand-hint 1,000,000 ops in 573ms, 1,745,624/sec, 572 ns/op, 26.4 MB, 27 bytes/op
tidwall: set-again 1,000,000 ops in 452ms, 2,212,581/sec, 451 ns/op, 27.1 MB, 28 bytes/op
tidwall: set-after-copy 1,000,000 ops in 472ms, 2,117,457/sec, 472 ns/op, 27.9 MB, 29 bytes/op
tidwall: load-rand 1,000,000 ops in 551ms, 1,816,498/sec, 550 ns/op, 26.1 MB, 27 bytes/op
** sequential get **
google: get-seq 1,000,000 ops in 133ms, 7,497,604/sec, 133 ns/op
tidwall: get-seq 1,000,000 ops in 110ms, 9,082,972/sec, 110 ns/op
tidwall: get-seq-hint 1,000,000 ops in 55ms, 18,289,945/sec, 54 ns/op
** random get **
google: get-rand 1,000,000 ops in 149ms, 6,704,337/sec, 149 ns/op
tidwall: get-rand 1,000,000 ops in 131ms, 7,616,296/sec, 131 ns/op
tidwall: get-rand-hint 1,000,000 ops in 216ms, 4,632,532/sec, 215 ns/op
You can find the benchmark utility at tidwall/btree-benchmark
Contact
Josh Baker @tidwall
License
Source code is available under the MIT License.