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[core] Use binary search to optimize SnapshotManager#earlierThanTimeMills #2805

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Feb 22, 2024
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[core] Use binary search to optimize SnapshotManager#earlierThanTimeMills #2805

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4fef1a1
[core] Use binary search to optimize SnapshotManager#earlierThanTimeM…
tsreaper Jan 29, 2024
1f1d20b
[fix] Add unit test
tsreaper Feb 21, 2024
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29 changes: 18 additions & 11 deletions paimon-core/src/main/java/org/apache/paimon/utils/SnapshotManager.java
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Original file line number Diff line number Diff line change
Expand Up @@ -181,23 +181,30 @@ public boolean snapshotExists(long snapshotId) {
}

/**
* Returns a snapshot earlier than the timestamp mills. A non-existent snapshot may be returned
* if all snapshots are later than the timestamp mills.
* Returns the latest snapshot earlier than the timestamp mills. A non-existent snapshot may be
* returned if all snapshots are equal to or later than the timestamp mills.
*/
public @Nullable Long earlierThanTimeMills(long timestampMills) {
Long earliest = earliestSnapshotId();
Long latest = latestSnapshotId();

if (earliest == null || latest == null) {
return null;
}

for (long i = latest; i >= earliest; i--) {
long commitTime = snapshot(i).timeMillis();
if (commitTime < timestampMills) {
return i;
if (snapshot(earliest).timeMillis() >= timestampMills) {
return earliest - 1;
}

while (earliest < latest) {
long mid = (earliest + latest + 1) / 2;
if (snapshot(mid).timeMillis() < timestampMills) {
earliest = mid;
} else {
latest = mid - 1;
}
}
return earliest - 1;
return earliest;
}

/**
Expand All @@ -214,7 +221,7 @@ public boolean snapshotExists(long snapshotId) {
if (snapshot(earliest).timeMillis() > timestampMills) {
return null;
}
Snapshot finnalSnapshot = null;
Snapshot finalSnapshot = null;
while (earliest <= latest) {
long mid = earliest + (latest - earliest) / 2; // Avoid overflow
Snapshot snapshot = snapshot(mid);
Expand All @@ -223,13 +230,13 @@ public boolean snapshotExists(long snapshotId) {
latest = mid - 1; // Search in the left half
} else if (commitTime < timestampMills) {
earliest = mid + 1; // Search in the right half
finnalSnapshot = snapshot;
finalSnapshot = snapshot;
} else {
finnalSnapshot = snapshot; // Found the exact match
finalSnapshot = snapshot; // Found the exact match
break;
}
}
return finnalSnapshot;
return finalSnapshot;
}

public long snapshotCount() throws IOException {
Expand Down
89 changes: 71 additions & 18 deletions paimon-core/src/test/java/org/apache/paimon/utils/SnapshotManagerTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -28,8 +28,12 @@

import java.io.IOException;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.atomic.AtomicReference;
import java.util.stream.Collectors;

import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.api.Assertions.fail;
Expand All @@ -49,6 +53,52 @@ public void testSnapshotPath() {
}
}

@Test
public void testEarlierThanTimeMillis() throws IOException {
long base = System.currentTimeMillis();
ThreadLocalRandom random = ThreadLocalRandom.current();

int numSnapshots = random.nextInt(1, 20);
Set<Long> set = new HashSet<>();
while (set.size() < numSnapshots) {
set.add(base + random.nextLong(0, 1_000_000));
}
List<Long> millis = set.stream().sorted().collect(Collectors.toList());

FileIO localFileIO = LocalFileIO.create();
SnapshotManager snapshotManager =
new SnapshotManager(localFileIO, new Path(tempDir.toString()));
int firstSnapshotId = random.nextInt(1, 100);
for (int i = 0; i < numSnapshots; i++) {
Snapshot snapshot = createSnapshotWithMillis(firstSnapshotId + i, millis.get(i));
localFileIO.writeFileUtf8(
snapshotManager.snapshotPath(firstSnapshotId + i), snapshot.toJson());
}

for (int tries = 0; tries < 10; tries++) {
long time;
if (random.nextBoolean()) {
// pick a random time
time = base + random.nextLong(0, 1_000_000);
} else {
// pick a random time equal to one of the snapshots
time = millis.get(random.nextInt(numSnapshots));
}
Long actual = snapshotManager.earlierThanTimeMills(time);

if (millis.get(numSnapshots - 1) < time) {
assertThat(actual).isEqualTo(firstSnapshotId + numSnapshots - 1);
} else {
for (int i = 0; i < numSnapshots; i++) {
if (millis.get(i) >= time) {
assertThat(actual).isEqualTo(firstSnapshotId + i - 1);
break;
}
}
}
}
}

@Test
public void testEarlierOrEqualTimeMills() throws IOException {
long millis = 1684726826L;
Expand All @@ -57,24 +107,7 @@ public void testEarlierOrEqualTimeMills() throws IOException {
new SnapshotManager(localFileIO, new Path(tempDir.toString()));
// create 10 snapshots
for (long i = 0; i < 10; i++) {
Snapshot snapshot =
new Snapshot(
i,
0L,
null,
null,
null,
null,
null,
0L,
Snapshot.CommitKind.APPEND,
millis + i * 1000,
null,
null,
null,
null,
null,
null);
Snapshot snapshot = createSnapshotWithMillis(i, millis + i * 1000);
localFileIO.writeFileUtf8(snapshotManager.snapshotPath(i), snapshot.toJson());
}
// smaller than the second snapshot return the first snapshot
Expand All @@ -88,6 +121,26 @@ public void testEarlierOrEqualTimeMills() throws IOException {
.isEqualTo(millis + 1000);
}

private Snapshot createSnapshotWithMillis(long id, long millis) {
return new Snapshot(
id,
0L,
null,
null,
null,
null,
null,
0L,
Snapshot.CommitKind.APPEND,
millis,
null,
null,
null,
null,
null,
null);
}

@Test
public void testTraversalSnapshotsFromLatestSafely() throws IOException, InterruptedException {
FileIO localFileIO = LocalFileIO.create();
Expand Down
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