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<?php

use DBDiff\DB\DBManager;

use DBDiff\Diff\AlterView;

use DBDiff\DB\Support\PostgresExpressionEquivalence;

use DBDiff\Migration\Config\DsnParser;

use DBDiff\Params\DefaultParams;

/**

* Deciding whether changed views are the same one rendered twice costs a

* fixed number of transactions, not several per view.

* Each rendering was its own begin, create, read and roll back, and across

* major versions the target renders two per view: about 1,600 round trips for

* 200 views, which over a 50 ms link nearly doubled a diff. Every view body is

* now rendered in one transaction per connection.

class ViewRenderingRoundTripsPostgresTest extends PostgresRoundTripTestCase

{

protected string $prefix = 'dbdiff_vrr';

private const VIEWS = 25;

public function testManyViewsAreRenderedInOneTransactionAndJudgedAsBefore(): void

{

if ($this->serverVersion < 150000) {

$this->markTestSkipped('pg_stat_force_next_flush() needs PostgreSQL 15.');

}

$tables = 'CREATE TABLE t (id int, n int, label text);';

$source = $this->db('s', $tables);

$target = $this->db('t', $tables);

$manager = new DBManager();

$params = new DefaultParams();

$params->driver = 'pgsql';

$s = DsnParser::toServerAndDb(DsnParser::parse($this->url($source)));

$t = DsnParser::toServerAndDb(DsnParser::parse($this->url($target)));

$params->server1 = $s['server'];

$params->server2 = $t['server'];

$params->input = ['kind' => 'db', 'source' => ['server' => 'server1', 'db' => $s['db']],

'target' => ['server' => 'server2', 'db' => $t['db']]];

$manager->connect($params);

$src = $manager->getDB('source');

$tgt = $manager->getDB('target');

// Half the views are the same query written two ways (equivalent), half

// genuinely differ, and one cannot be built at all.

$diffs = [];

for ($i = 0; $i < self::VIEWS; $i++) {

$same = $i % 2 === 0;

$diffs[] = new AlterView("v$i",

"CREATE VIEW \"v$i\" AS SELECT t.id FROM t WHERE (t.n > $i)",

$same ? "CREATE VIEW \"v$i\" AS SELECT id FROM t WHERE n > $i" : "CREATE VIEW \"v$i\" AS SELECT id FROM t WHERE n < $i");

}

$diffs[] = new AlterView('broken', 'CREATE VIEW "broken" AS SELECT nope FROM missing', 'CREATE VIEW "broken" AS SELECT 1');

// The flush happens once the statement asking for it has finished, so

// the count is read by a second one.

$rollbacks = function () use ($tgt): int {

$tgt->select('SELECT pg_stat_force_next_flush()');

return (int) $tgt->selectOne(

'SELECT xact_rollback FROM pg_stat_database WHERE datname = current_database()')['xact_rollback'];

};

$before = $rollbacks();

$kept = PostgresExpressionEquivalence::dropEquivalent($diffs, $src, $tgt);

$after = $rollbacks();

$this->assertSame(

array_merge(array_map(fn($i) => "v$i", range(1, self::VIEWS - 1, 2)), ['broken']),

array_map(fn($d) => $d->name, $kept)

);

$this->assertLessThan(5, $after - $before, 'transactions rolled back on the target while rendering');

}

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