Fix incorrect syntax for dropping primary indexes in PostgreSQL

src/Platforms/PostgreSQLPlatform.php

@@ -809,6 +809,22 @@ public function getDropForeignKeySQL($foreignKey, $table)
         return $this->getDropConstraintSQL($foreignKey, $table);
     }
 
+    /**
+     * {@inheritDoc}
+     */
+    public function getDropIndexSQL($index, $table = null)
+    {
+        if ($index instanceof Index && $index->isPrimary()) {
+            $constraintName = 'primary' === $index->getName() ? $table . '_pkey' : $index->getName();
+            return $this->getDropConstraintSQL($constraintName, $table);
+        } elseif (is_string($index) && '"primary"' === $index) {
+            $constraintName = $table . '_pkey';
+            return $this->getDropConstraintSQL($constraintName, $table);
+        }
+
+        return parent::getDropIndexSQL($index, $table);
+    }
+
     /**
      * {@inheritDoc}
      */

tests/Functional/Driver/PDO/PgSQL/DBAL6024Test.php

@@ -0,0 +1,52 @@
+<?php
+
+namespace Doctrine\DBAL\Tests\Functional\Driver\PDO\PgSQL;
+
+use Doctrine\DBAL\DriverManager;
+use Doctrine\DBAL\Schema\Comparator;
+use Doctrine\DBAL\Schema\Table;
+use Doctrine\DBAL\Tests\FunctionalTestCase;
+use Doctrine\DBAL\Tests\TestUtil;
+
+/**
+ * How to run this test:
+ * 1) Start a PostgreSQLInstance
+ * 2) If needed, change ci/github/phpunit/pdo_pgsql.xml according to your PostgreSQL local settings
+ * 3) Run
+ * vendor/bin/phpunit -c ci/github/phpunit/pdo_pgsql.xml tests/Functional/Driver/PDO/PgSQL/DBAL6024Test.php
+ */
+
+/** @requires extension pdo_pgsql */
+class DBAL6024Test extends FunctionalTestCase
+{
+    protected function setUp(): void
+    {
+        if (TestUtil::isDriverOneOf('pdo_pgsql')) {
+            return;
+        }
+
+        self::markTestSkipped('This test requires the pdo_pgsql driver.');
+    }
+
+    public function testDropPrimaryKey(): void
+    {
+        $table = new Table('mytable');
+        $table->addColumn('id', 'integer');
+        $table->setPrimaryKey(['id']);
+        $this->dropAndCreateTable($table);
+
+        $newTable = clone $table;
+        $newTable->dropPrimaryKey();
+
+        xdebug_break();
+
+        $diff = (new Comparator())->compareTables($table, $newTable);
+
+        $statements = $this->connection->getDatabasePlatform()->getAlterTableSQL($diff);
+        foreach ($statements as $statement) {
+            $this->connection->executeStatement($statement);
+        }
+
+        $this->assertTrue($this->count($statements) > 0);
+    }
+}

tests/Platforms/PostgreSQLPlatformTest.php

@@ -581,6 +581,48 @@ public function testDroppingConstraintsBeforeColumns(): void
         self::assertEquals($expectedSql, $sql);
     }
 
+    public function testDroppingPrimaryKey(): void
+    {
+        $oldTable = new Table('mytable');
+        $oldTable->addColumn('id', 'integer');
+        $oldTable->setPrimaryKey(['id']);
+
+        $newTable = clone $oldTable;
+        $newTable->dropPrimaryKey();
+
+        $diff = (new Comparator())->compareTables($oldTable, $newTable);
+         self::assertNotFalse($diff);
+
+        $sql = $this->platform->getAlterTableSQL($diff);
+
+        $expectedSql = [
+            'ALTER TABLE mytable DROP CONSTRAINT mytable_pkey',
+        ];
+
+        self::assertEquals($expectedSql, $sql);
+    }
+
+    public function testDroppingPrimaryKeyWithUserDefinedName(): void
+    {
+        $oldTable = new Table('mytable');
+        $oldTable->addColumn('id', 'integer');
+        $oldTable->setPrimaryKey(['id'], 'a_user_name');
+
+        $newTable = clone $oldTable;
+        $newTable->dropPrimaryKey();
+
+        $diff = (new Comparator())->compareTables($oldTable, $newTable);
+         self::assertNotFalse($diff);
+
+        $sql = $this->platform->getAlterTableSQL($diff);
+
+        $expectedSql = [
+            'ALTER TABLE mytable DROP CONSTRAINT a_user_name',
+        ];
+
+        self::assertEquals($expectedSql, $sql);
+    }
+
     public function testUsesSequenceEmulatedIdentityColumns(): void
     {
         self::assertTrue($this->platform->usesSequenceEmulatedIdentityColumns());