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// Copyright 2013 The LevelDB-Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package db
import (
"bytes"
"errors"
"fmt"
"math/rand"
"strings"
"testing"
)
var testKeyValuePairs = []string{
"10:ten",
"11:eleven",
"12:twelve",
"13:thirteen",
"14:fourteen",
"15:fifteen",
"16:sixteen",
"17:seventeen",
"18:eighteen",
"19:nineteen",
}
type fakeIter struct {
kvPairs []string
index int
closeErr error
}
func newFakeIterator(closeErr error, kvPairs ...string) *fakeIter {
for _, kv := range kvPairs {
if !strings.Contains(kv, ":") {
panic(fmt.Sprintf(`key-value pair %q does not contain ":"`, kv))
}
}
return &fakeIter{
kvPairs: kvPairs,
index: -1,
closeErr: closeErr,
}
}
func (f *fakeIter) Next() bool {
f.index++
return f.index < len(f.kvPairs)
}
func (f *fakeIter) Key() []byte {
kv := f.kvPairs[f.index]
i := strings.Index(kv, ":")
return []byte(kv[:i])
}
func (f *fakeIter) Value() []byte {
kv := f.kvPairs[f.index]
i := strings.Index(kv, ":")
return []byte(kv[i+1:])
}
func (f *fakeIter) Close() error {
return f.closeErr
}
// testIterator tests creating a combined iterator from a number of sub-
// iterators. newFunc is a constructor function. splitFunc returns a random
// split of the testKeyValuePairs slice such that walking a combined iterator
// over those splits should recover the original key/value pairs in order.
func testIterator(t *testing.T, newFunc func(...Iterator) Iterator, splitFunc func(r *rand.Rand) [][]string) {
// Test pre-determined sub-iterators. The sub-iterators are designed
// so that the combined key/value pair order is the same whether the
// combined iterator is concatenating or merging.
testCases := []struct {
desc string
iters []Iterator
want string
}{
{
"one sub-iterator",
[]Iterator{
newFakeIterator(nil, "e:east", "w:west"),
},
"<e:east><w:west>.",
},
{
"two sub-iterators",
[]Iterator{
newFakeIterator(nil, "a0:0"),
newFakeIterator(nil, "b1:1", "b2:2"),
},
"<a0:0><b1:1><b2:2>.",
},
{
"empty sub-iterators",
[]Iterator{
newFakeIterator(nil),
newFakeIterator(nil),
newFakeIterator(nil),
},
".",
},
{
"sub-iterator errors",
[]Iterator{
newFakeIterator(nil, "a0:0", "a1:1"),
newFakeIterator(errors.New("the sky is falling!"), "b2:2", "b3:3", "b4:4"),
newFakeIterator(errors.New("run for your lives!"), "c5:5", "c6:6"),
},
"<a0:0><a1:1><b2:2><b3:3><b4:4>err=the sky is falling!",
},
}
for _, tc := range testCases {
var b bytes.Buffer
iter := newFunc(tc.iters...)
for iter.Next() {
fmt.Fprintf(&b, "<%s:%s>", iter.Key(), iter.Value())
}
if err := iter.Close(); err != nil {
fmt.Fprintf(&b, "err=%v", err)
} else {
b.WriteByte('.')
}
if got := b.String(); got != tc.want {
t.Errorf("%s:\ngot %q\nwant %q", tc.desc, got, tc.want)
}
}
// Test randomly generated sub-iterators.
r := rand.New(rand.NewSource(0))
for i, nBad := 0, 0; i < 1000; i++ {
bad := false
splits := splitFunc(r)
iters := make([]Iterator, len(splits))
for i, split := range splits {
iters[i] = newFakeIterator(nil, split...)
}
iter := newFunc(iters...)
j := 0
for ; iter.Next() && j < len(testKeyValuePairs); j++ {
got := string(iter.Key()) + ":" + string(iter.Value())
want := testKeyValuePairs[j]
if got != want {
bad = true
t.Errorf("random splits: i=%d, j=%d: got %q, want %q", i, j, got, want)
}
}
if iter.Next() {
bad = true
t.Errorf("random splits: i=%d, j=%d: iter was not exhausted", i, j)
}
if j != len(testKeyValuePairs) {
bad = true
t.Errorf("random splits: i=%d, j=%d: want j=%d", i, j, len(testKeyValuePairs))
}
if err := iter.Close(); err != nil {
bad = true
t.Errorf("random splits: i=%d, j=%d: %v", i, j, err)
}
if bad {
nBad++
if nBad == 10 {
t.Fatal("random splits: too many errors; stopping")
}
}
}
}
func TestConcatenatingIterator(t *testing.T) {
testIterator(t, NewConcatenatingIterator, func(r *rand.Rand) [][]string {
// Partition testKeyValuePairs into one or more splits. Each individual
// split is in increasing order, and different splits may not overlap
// in range. Some of the splits may be empty.
splits, remainder := [][]string{}, testKeyValuePairs
for r.Intn(4) != 0 {
i := r.Intn(1 + len(remainder))
splits = append(splits, remainder[:i])
remainder = remainder[i:]
}
if len(remainder) > 0 {
splits = append(splits, remainder)
}
return splits
})
}
func TestMergingIterator(t *testing.T) {
newFunc := func(iters ...Iterator) Iterator {
return NewMergingIterator(DefaultComparer, iters...)
}
testIterator(t, newFunc, func(r *rand.Rand) [][]string {
// Shuffle testKeyValuePairs into one or more splits. Each individual
// split is in increasing order, but different splits may overlap in
// range. Some of the splits may be empty.
splits := make([][]string, 1+r.Intn(2+len(testKeyValuePairs)))
for _, kv := range testKeyValuePairs {
j := r.Intn(len(splits))
splits[j] = append(splits[j], kv)
}
return splits
})
}
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