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jmikolajmikola
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PHPLIB-789: Snapshot query examples (#900)
Includes work-arounds for SnapshotUnavailable(246) errors on replica sets and sharded clusters. Update spec links for StaleDbVersion workaround
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‎tests/DocumentationExamplesTest.php

+154
Original file line numberDiff line numberDiff line change
@@ -4,13 +4,16 @@
44

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use MongoDB\BSON\ObjectId;
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use MongoDB\BSON\UTCDateTime;
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use MongoDB\Collection;
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use MongoDB\Database;
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use MongoDB\Driver\Cursor;
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use MongoDB\Driver\Exception\CommandException;
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use MongoDB\Driver\Exception\Exception;
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use MongoDB\Driver\ReadPreference;
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use MongoDB\Driver\WriteConcern;
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use function in_array;
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use function microtime;
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use function ob_end_clean;
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use function ob_start;
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use function var_dump;
@@ -1571,6 +1574,119 @@ public function testCausalConsistency(): void
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ob_end_clean();
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}
15731576

1577+
public function testSnapshotQueries(): void
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{
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if (version_compare($this->getServerVersion(), '5.0.0', '<')) {
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$this->markTestSkipped('Snapshot queries outside of transactions are not supported');
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}
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if (! ($this->isReplicaSet() || $this->isShardedClusterUsingReplicasets())) {
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$this->markTestSkipped('Snapshot read concern is only supported with replicasets');
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}
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$client = static::createTestClient();
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$catsCollection = $client->selectCollection('pets', 'cats');
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$catsCollection->drop();
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$catsCollection->insertMany([
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['name' => 'Whiskers', 'color' => 'white', 'adoptable' => true],
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['name' => 'Garfield', 'color' => 'orange', 'adoptable' => false],
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]);
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$dogsCollection = $client->selectCollection('pets', 'dogs');
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$dogsCollection->drop();
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$dogsCollection->insertMany([
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['name' => 'Toto', 'color' => 'black', 'adoptable' => true],
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['name' => 'Milo', 'color' => 'black', 'adoptable' => false],
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['name' => 'Brian', 'color' => 'white', 'adoptable' => true],
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]);
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if ($this->isShardedCluster()) {
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$this->preventStaleDbVersionError('pets', 'cats');
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$this->preventStaleDbVersionError('pets', 'dogs');
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} else {
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$this->waitForSnapshot('pets', 'cats');
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$this->waitForSnapshot('pets', 'dogs');
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}
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ob_start();
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// Start Snapshot Query Example 1
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$catsCollection = $client->selectCollection('pets', 'cats');
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$dogsCollection = $client->selectCollection('pets', 'dogs');
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$session = $client->startSession(['snapshot' => true]);
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$adoptablePetsCount = $catsCollection->aggregate(
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[
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['$match' => ['adoptable' => true]],
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['$count' => 'adoptableCatsCount'],
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],
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['session' => $session]
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)->toArray()[0]->adoptableCatsCount;
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$adoptablePetsCount += $dogsCollection->aggregate(
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[
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['$match' => ['adoptable' => true]],
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['$count' => 'adoptableDogsCount'],
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],
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['session' => $session]
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)->toArray()[0]->adoptableDogsCount;
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var_dump($adoptablePetsCount);
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// End Snapshot Query Example 1
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ob_end_clean();
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$this->assertSame(3, $adoptablePetsCount);
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$catsCollection->drop();
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$dogsCollection->drop();
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$salesCollection = $client->selectCollection('retail', 'sales');
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$salesCollection->drop();
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$salesCollection->insertMany([
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['shoeType' => 'boot', 'price' => 30, 'saleDate' => new UTCDateTime()],
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]);
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if ($this->isShardedCluster()) {
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$this->preventStaleDbVersionError('retail', 'sales');
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} else {
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$this->waitForSnapshot('retail', 'sales');
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}
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// Start Snapshot Query Example 2
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$salesCollection = $client->selectCollection('retail', 'sales');
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$session = $client->startSession(['snapshot' => true]);
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$totalDailySales = $salesCollection->aggregate(
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[
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[
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'$match' => [
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'$expr' => [
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'$gt' => ['$saleDate', [
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'$dateSubtract' => [
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'startDate' => '$$NOW',
1671+
'unit' => 'day',
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'amount' => 1,
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],
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],
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],
1676+
],
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],
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],
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['$count' => 'totalDailySales'],
1680+
],
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['session' => $session]
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)->toArray()[0]->totalDailySales;
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// End Snapshot Query Example 2
1684+
1685+
$this->assertSame(1, $totalDailySales);
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1687+
$salesCollection->drop();
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}
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15741690
/**
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* @doesNotPerformAssertions
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*/
@@ -1747,4 +1863,42 @@ private function assertInventoryCount($count): void
17471863
{
17481864
$this->assertCollectionCount($this->getDatabaseName() . '.' . $this->getCollectionName(), $count);
17491865
}
1866+
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private function waitForSnapshot(string $databaseName, string $collectionName): void
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{
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$collection = new Collection($this->manager, $databaseName, $collectionName);
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$session = $this->manager->startSession(['snapshot' => true]);
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1872+
/* Retry until a snapshot query succeeds or ten seconds elapse,
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* whichwever comes first.
1874+
*
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* TODO: use hrtime() once the library requires PHP 7.3+ */
1876+
$retryUntil = microtime(true) + 10;
1877+
1878+
do {
1879+
try {
1880+
$collection->aggregate(
1881+
[['$match' => ['_id' => ['$exists' => true]]]],
1882+
['session' => $session]
1883+
);
1884+
1885+
break;
1886+
} catch (CommandException $e) {
1887+
if ($e->getCode() === 246 /* SnapshotUnavailable */) {
1888+
continue;
1889+
}
1890+
1891+
throw $e;
1892+
}
1893+
} while (microtime(true) < $retryUntil);
1894+
}
1895+
1896+
/**
1897+
* @see https://jira.mongodb.org/browse/SERVER-39704
1898+
*/
1899+
private function preventStaleDbVersionError(string $databaseName, string $collectionName): void
1900+
{
1901+
$collection = new Collection($this->manager, $databaseName, $collectionName);
1902+
$collection->distinct('foo');
1903+
}
17501904
}

‎tests/SpecTests/TransactionsSpecTest.php

+1-1
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@@ -353,7 +353,7 @@ private static function killAllSessions(): void
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* Work around potential error executing distinct on sharded clusters.
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*
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* @param array $operations
356-
* @see https://github.com/mongodb/specifications/tree/master/source/transactions/tests#why-do-tests-that-run-distinct-sometimes-fail-with-staledbversionts.
356+
* @see https://github.com/mongodb/specifications/tree/master/source/transactions/tests#why-do-tests-that-run-distinct-sometimes-fail-with-staledbversion
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*/
358358
private function preventStaleDbVersionError(array $operations): void
359359
{

‎tests/UnifiedSpecTests/UnifiedTestRunner.php

+1-1
Original file line numberDiff line numberDiff line change
@@ -442,7 +442,7 @@ private function prepareInitialData(array $initialData): void
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/**
443443
* Work around potential error executing distinct on sharded clusters.
444444
*
445-
* @see https://github.com/mongodb/specifications/blob/master/source/transactions/tests/README.rst#why-do-tests-that-run-distinct-sometimes-fail-with-staledbversion
445+
* @see https://github.com/mongodb/specifications/blob/master/source/unified-test-format/unified-test-format.rst#staledbversion-errors-on-sharded-clusters
446446
*/
447447
private function preventStaleDbVersionError(array $operations, Context $context): void
448448
{

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