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util/shuffle, kv, storage: Adds a shuffle package for randomizing lists.
Also, add a shuffle to the store pool's getStoreList. Relying on the range over a map to ensure randomness is a little too subtle. This is much more explisit. Part of cockroachdb#10275
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,36 @@ | ||
| // Copyright 2016 The Cockroach Authors. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or | ||
| // implied. See the License for the specific language governing | ||
| // permissions and limitations under the License. | ||
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| package shuffle | ||
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| import "math/rand" | ||
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| // Interface for shuffle. When it is satisfied, a collection can be shuffled by | ||
| // the routines in this package. The methods require that the elements of the | ||
| // collection be enumerable by an integer index. This interface is similar to | ||
| // sort.Interface. | ||
| type Interface interface { | ||
| // Len is the number of elements in the collection. | ||
| Len() int | ||
| // Swap swaps the elements with indexes i and j. | ||
| Swap(i, j int) | ||
| } | ||
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| // Shuffle randomizes the order of the array. | ||
| func Shuffle(data Interface) { | ||
| n := data.Len() | ||
| for i := 1; i < n; i++ { | ||
| data.Swap(i, rand.Intn(i+1)) | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,80 @@ | ||
| // Copyright 2016 The Cockroach Authors. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or | ||
| // implied. See the License for the specific language governing | ||
| // permissions and limitations under the License. | ||
|
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| package shuffle | ||
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| import ( | ||
| "math/rand" | ||
| "reflect" | ||
| "testing" | ||
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| "github.com/cockroachdb/cockroach/pkg/util/leaktest" | ||
| ) | ||
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| type testSlice []int | ||
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| // testSlice implements shuffle.Interface. | ||
| func (ts testSlice) Len() int { return len(ts) } | ||
| func (ts testSlice) Swap(i, j int) { ts[i], ts[j] = ts[j], ts[i] } | ||
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| func TestShuffle(t *testing.T) { | ||
| defer leaktest.AfterTest(t)() | ||
| rand.Seed(0) | ||
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| verify := func(original, expected testSlice) { | ||
| Shuffle(original) | ||
| if !reflect.DeepEqual(original, expected) { | ||
| t.Errorf("expected %v, got %v", expected, original) | ||
| } | ||
| } | ||
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| ts := testSlice{} | ||
| verify(ts, testSlice{}) | ||
| verify(ts, testSlice{}) | ||
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| ts = testSlice{1} | ||
| verify(ts, testSlice{1}) | ||
| verify(ts, testSlice{1}) | ||
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| ts = testSlice{1, 2} | ||
| verify(ts, testSlice{2, 1}) | ||
| verify(ts, testSlice{1, 2}) | ||
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| ts = testSlice{1, 2, 3} | ||
| verify(ts, testSlice{1, 3, 2}) | ||
| verify(ts, testSlice{1, 2, 3}) | ||
| verify(ts, testSlice{1, 2, 3}) | ||
| verify(ts, testSlice{3, 1, 2}) | ||
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| ts = testSlice{1, 2, 3, 4, 5} | ||
| verify(ts, testSlice{2, 1, 3, 5, 4}) | ||
| verify(ts, testSlice{4, 2, 1, 5, 3}) | ||
| verify(ts, testSlice{1, 4, 2, 3, 5}) | ||
| verify(ts, testSlice{2, 5, 4, 1, 3}) | ||
| verify(ts, testSlice{4, 2, 3, 1, 5}) | ||
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| verify(ts[2:2], testSlice{}) | ||
| verify(ts[0:0], testSlice{}) | ||
| verify(ts[5:5], testSlice{}) | ||
| verify(ts[3:5], testSlice{1, 5}) | ||
| verify(ts[3:5], testSlice{5, 1}) | ||
| verify(ts[0:2], testSlice{4, 2}) | ||
| verify(ts[0:2], testSlice{2, 4}) | ||
| verify(ts[1:4], testSlice{3, 5, 4}) | ||
| verify(ts[1:4], testSlice{5, 4, 3}) | ||
| verify(ts[0:4], testSlice{4, 5, 2, 3}) | ||
| verify(ts[0:4], testSlice{2, 4, 3, 5}) | ||
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| verify(ts, testSlice{1, 3, 4, 2, 5}) | ||
| } |