From e7b326cfd6f6c2da2fee8b7bd71ec4c3dc4cc938 Mon Sep 17 00:00:00 2001
From: Sergei Morozov <morozov@tut.by>
Date: Thu, 1 Sep 2022 12:32:45 -0700
Subject: [PATCH] Remove property-based schema comparison APIs

---
 UPGRADE.md                                    |   8 +-
 phpcs.xml.dist                                |   2 +-
 psalm.xml.dist                                |  13 --
 src/Schema/ColumnDiff.php                     |  70 +++++-----
 src/Schema/Comparator.php                     |  99 --------------
 .../Schema/SQLServerSchemaManagerTest.php     |   5 -
 .../SchemaManagerFunctionalTestCase.php       |   2 -
 .../AbstractMySQLPlatformTestCase.php         |  12 --
 tests/Platforms/AbstractPlatformTestCase.php  |  51 -------
 tests/Platforms/DB2PlatformTest.php           |  73 ++++-------
 tests/Platforms/OraclePlatformTest.php        |  14 --
 tests/Platforms/PostgreSQLPlatformTest.php    |  18 ---
 tests/Platforms/SQLServerPlatformTestCase.php |  41 ------
 tests/Platforms/SQLitePlatformTest.php        |  18 ---
 tests/Schema/ComparatorTest.php               | 124 +++++-------------
 15 files changed, 107 insertions(+), 443 deletions(-)

diff --git a/UPGRADE.md b/UPGRADE.md
index 95570e82982..aae5a83681e 100644
--- a/UPGRADE.md
+++ b/UPGRADE.md
@@ -537,9 +537,13 @@ Instead of returning an empty value, `Connection::lastInsertId()` throws an exce
 
 The method `Comparator::compareSchemas()` cannot be called statically anymore.
 
-## Removed `Comparator::compare()`
+## Removed `Comparator` methods
 
-The method `Comparator::compare()` has been removed, use `Comparator::compareSchemas()` instead.
+The `Comparator::compare()` and `::diffColumn()` methods have been removed.
+
+## Removed `ColumnDiff` methods
+
+The `ColumnDiff::hasChanged()` method has been removed.
 
 ## Removed `TableGenerator` component
 
diff --git a/phpcs.xml.dist b/phpcs.xml.dist
index c5292eae51e..9c1f13f8891 100644
--- a/phpcs.xml.dist
+++ b/phpcs.xml.dist
@@ -106,7 +106,7 @@
 
     <!-- see https://github.com/doctrine/dbal/issues/3377 -->
     <rule ref="SlevomatCodingStandard.Operators.DisallowEqualOperators.DisallowedNotEqualOperator">
-        <exclude-pattern>src/Schema/Comparator.php</exclude-pattern>
+        <exclude-pattern>src/Schema/ColumnDiff.php</exclude-pattern>
     </rule>
 
     <!-- The SQLSRV_* functions are defined in the upper case by the sqlsrv extension and violate the standard
diff --git a/psalm.xml.dist b/psalm.xml.dist
index 5db2e2b305d..f6e62d924bb 100644
--- a/psalm.xml.dist
+++ b/psalm.xml.dist
@@ -39,21 +39,8 @@
                     See https://github.com/doctrine/dbal/pull/4317
                 -->
                 <file name="tests/Functional/LegacyAPITest.php"/>
-                <!--
-                    TODO: remove in 4.0.0
-                -->
-                <referencedMethod name="Doctrine\DBAL\Schema\ColumnDiff::hasChanged"/>
-                <referencedMethod name="Doctrine\DBAL\Schema\Comparator::diffColumn"/>
             </errorLevel>
         </DeprecatedMethod>
-        <DeprecatedProperty>
-            <errorLevel type="suppress">
-                <!--
-                    TODO: remove in 4.0.0
-                -->
-                <referencedProperty name="Doctrine\DBAL\Schema\ColumnDiff::$changedProperties"/>
-            </errorLevel>
-        </DeprecatedProperty>
         <DocblockTypeContradiction>
             <errorLevel type="suppress">
                 <!--
diff --git a/src/Schema/ColumnDiff.php b/src/Schema/ColumnDiff.php
index aca7056a643..d770f4040a3 100644
--- a/src/Schema/ColumnDiff.php
+++ b/src/Schema/ColumnDiff.php
@@ -4,8 +4,6 @@
 
 namespace Doctrine\DBAL\Schema;
 
-use function in_array;
-
 /**
  * Represents the change of a column.
  */
@@ -13,78 +11,88 @@ class ColumnDiff
 {
     /**
      * @internal The diff can be only instantiated by a {@see Comparator}.
-     *
-     * @param array<string> $changedProperties
      */
-    public function __construct(
-        public Column $column,
-        /**
-         * @deprecated Use {@see hasTypeChanged()}, {@see hasLengthChanged()}, {@see hasPrecisionChanged()},
-         * {@see hasScaleChanged()}, {@see hasUnsignedChanged()}, {@see hasFixedChanged()}, {@see hasNotNullChanged()},
-         * {@see hasDefaultChanged()}, {@see hasAutoIncrementChanged()} or {@see hasCommentChanged()} instead.
-         */
-        public array $changedProperties,
-        public Column $fromColumn,
-    ) {
+    public function __construct(public Column $column, public Column $fromColumn)
+    {
     }
 
     public function hasTypeChanged(): bool
     {
-        return $this->hasChanged('type');
+        return $this->column->getType()::class !== $this->fromColumn->getType()::class;
     }
 
     public function hasLengthChanged(): bool
     {
-        return $this->hasChanged('length');
+        return $this->hasPropertyChanged(static function (Column $column): ?int {
+            return $column->getLength();
+        });
     }
 
     public function hasPrecisionChanged(): bool
     {
-        return $this->hasChanged('precision');
+        return $this->hasPropertyChanged(static function (Column $column): ?int {
+            return $column->getPrecision();
+        });
     }
 
     public function hasScaleChanged(): bool
     {
-        return $this->hasChanged('scale');
+        return $this->hasPropertyChanged(static function (Column $column): int {
+            return $column->getScale();
+        });
     }
 
     public function hasUnsignedChanged(): bool
     {
-        return $this->hasChanged('unsigned');
+        return $this->hasPropertyChanged(static function (Column $column): bool {
+            return $column->getUnsigned();
+        });
     }
 
     public function hasFixedChanged(): bool
     {
-        return $this->hasChanged('fixed');
+        return $this->hasPropertyChanged(static function (Column $column): bool {
+            return $column->getFixed();
+        });
     }
 
     public function hasNotNullChanged(): bool
     {
-        return $this->hasChanged('notnull');
+        return $this->hasPropertyChanged(static function (Column $column): bool {
+            return $column->getNotnull();
+        });
     }
 
     public function hasDefaultChanged(): bool
     {
-        return $this->hasChanged('default');
+        $oldDefault = $this->fromColumn->getDefault();
+        $newDefault = $this->column->getDefault();
+
+        // Null values need to be checked additionally as they tell whether to create or drop a default value.
+        // null != 0, null != false, null != '' etc. This affects platform's table alteration SQL generation.
+        if (($newDefault === null) xor ($oldDefault === null)) {
+            return true;
+        }
+
+        return $newDefault != $oldDefault;
     }
 
     public function hasAutoIncrementChanged(): bool
     {
-        return $this->hasChanged('autoincrement');
+        return $this->hasPropertyChanged(static function (Column $column): bool {
+            return $column->getAutoincrement();
+        });
     }
 
     public function hasCommentChanged(): bool
     {
-        return $this->hasChanged('comment');
+        return $this->hasPropertyChanged(static function (Column $column): string {
+            return $column->getComment();
+        });
     }
 
-    /**
-     * @deprecated Use {@see hasTypeChanged()}, {@see hasLengthChanged()}, {@see hasPrecisionChanged()},
-     * {@see hasScaleChanged()}, {@see hasUnsignedChanged()}, {@see hasFixedChanged()}, {@see hasNotNullChanged()},
-     * {@see hasDefaultChanged()}, {@see hasAutoIncrementChanged()} or {@see hasCommentChanged()} instead.
-     */
-    public function hasChanged(string $propertyName): bool
+    private function hasPropertyChanged(callable $property): bool
     {
-        return in_array($propertyName, $this->changedProperties, true);
+        return $property($this->column) !== $property($this->fromColumn);
     }
 }
diff --git a/src/Schema/Comparator.php b/src/Schema/Comparator.php
index f7db444c341..32f30225b5f 100644
--- a/src/Schema/Comparator.php
+++ b/src/Schema/Comparator.php
@@ -6,13 +6,8 @@
 
 use Doctrine\DBAL\Exception;
 use Doctrine\DBAL\Platforms\AbstractPlatform;
-use Doctrine\DBAL\Types;
-use Doctrine\Deprecations\Deprecation;
 
-use function array_intersect_key;
-use function array_keys;
 use function array_map;
-use function array_unique;
 use function assert;
 use function count;
 use function strtolower;
@@ -221,7 +216,6 @@ public function diffTable(Table $fromTable, Table $toTable): ?TableDiff
 
             $tableDifferences->changedColumns[$column->getName()] = new ColumnDiff(
                 $toColumn,
-                $this->diffColumn($column, $toColumn),
                 $column,
             );
 
@@ -419,99 +413,6 @@ protected function columnsEqual(Column $column1, Column $column2): bool
         return $this->platform->columnsEqual($column1, $column2);
     }
 
-    /**
-     * Returns the difference between the columns
-     *
-     * If there are differences this method returns the changed properties as a
-     * string array, otherwise an empty array gets returned.
-     *
-     * @deprecated Use {@see diffTable()} instead.
-     *
-     * @return array<int, string>
-     */
-    public function diffColumn(Column $column1, Column $column2): array
-    {
-        Deprecation::triggerIfCalledFromOutside(
-            'doctrine/dbal',
-            'https://github.com/doctrine/dbal/pull/5650',
-            '%s is deprecated. Use diffTable() instead.',
-            __METHOD__,
-        );
-
-        $properties1 = $column1->toArray();
-        $properties2 = $column2->toArray();
-
-        $changedProperties = [];
-
-        if ($properties1['type']::class !== $properties2['type']::class) {
-            $changedProperties[] = 'type';
-        }
-
-        foreach (['notnull', 'unsigned', 'autoincrement'] as $property) {
-            if ($properties1[$property] === $properties2[$property]) {
-                continue;
-            }
-
-            $changedProperties[] = $property;
-        }
-
-        // Null values need to be checked additionally as they tell whether to create or drop a default value.
-        // null != 0, null != false, null != '' etc. This affects platform's table alteration SQL generation.
-        if (
-            ($properties1['default'] === null) !== ($properties2['default'] === null)
-            || $properties1['default'] != $properties2['default']
-        ) {
-            $changedProperties[] = 'default';
-        }
-
-        if (
-            ($properties1['type'] instanceof Types\StringType && ! $properties1['type'] instanceof Types\GuidType) ||
-            $properties1['type'] instanceof Types\BinaryType
-        ) {
-            if (
-                (isset($properties1['length']) !== isset($properties2['length']))
-                || (isset($properties1['length']) && isset($properties2['length'])
-                    && $properties1['length'] !== $properties2['length'])
-            ) {
-                $changedProperties[] = 'length';
-            }
-
-            if ($properties1['fixed'] !== $properties2['fixed']) {
-                $changedProperties[] = 'fixed';
-            }
-        } elseif ($properties1['type'] instanceof Types\DecimalType) {
-            if ($properties1['precision'] !== $properties2['precision']) {
-                $changedProperties[] = 'precision';
-            }
-
-            if ($properties1['scale'] !== $properties2['scale']) {
-                $changedProperties[] = 'scale';
-            }
-        }
-
-        // A null value and an empty string are actually equal for a comment so they should not trigger a change.
-        if (
-            $properties1['comment'] !== $properties2['comment'] &&
-            ! ($properties1['comment'] === null && $properties2['comment'] === '') &&
-            ! ($properties2['comment'] === null && $properties1['comment'] === '')
-        ) {
-            $changedProperties[] = 'comment';
-        }
-
-        $platformOptions1 = $column1->getPlatformOptions();
-        $platformOptions2 = $column2->getPlatformOptions();
-
-        foreach (array_keys(array_intersect_key($platformOptions1, $platformOptions2)) as $key) {
-            if ($properties1[$key] === $properties2[$key]) {
-                continue;
-            }
-
-            $changedProperties[] = $key;
-        }
-
-        return array_unique($changedProperties);
-    }
-
     /**
      * Finds the difference between the indexes $index1 and $index2.
      *
diff --git a/tests/Functional/Schema/SQLServerSchemaManagerTest.php b/tests/Functional/Schema/SQLServerSchemaManagerTest.php
index 7c869eb89a2..015d2360034 100644
--- a/tests/Functional/Schema/SQLServerSchemaManagerTest.php
+++ b/tests/Functional/Schema/SQLServerSchemaManagerTest.php
@@ -100,12 +100,10 @@ public function testDefaultConstraints(): void
             [
                 'df_integer' => new ColumnDiff(
                     new Column('df_integer', Type::getType('integer'), ['default' => 0]),
-                    ['default'],
                     new Column('df_integer', Type::getType('integer'), ['default' => 666]),
                 ),
                 'df_string_2' => new ColumnDiff(
                     new Column('df_string_2', Type::getType('string'), ['length' => 32]),
-                    ['default'],
                     new Column('df_string_2', Type::getType('string'), [
                         'length' => 32,
                         'default' => 'Doctrine rocks!!!',
@@ -116,7 +114,6 @@ public function testDefaultConstraints(): void
                         'length' => 50,
                         'default' => 'another default value',
                     ]),
-                    ['length'],
                     new Column('df_string_3', Type::getType('string'), [
                         'length' => 50,
                         'default' => 'another default value',
@@ -124,7 +121,6 @@ public function testDefaultConstraints(): void
                 ),
                 'df_boolean' => new ColumnDiff(
                     new Column('df_boolean', Type::getType('boolean'), ['default' => false]),
-                    ['default'],
                     new Column('df_boolean', Type::getType('boolean'), ['default' => true]),
                 ),
             ],
@@ -162,7 +158,6 @@ public function testDefaultConstraints(): void
             [
                 'df_integer' => new ColumnDiff(
                     new Column('df_integer', Type::getType('integer'), ['default' => 666]),
-                    ['default'],
                     new Column('df_integer', Type::getType('integer'), ['default' => 0]),
                 ),
             ],
diff --git a/tests/Functional/Schema/SchemaManagerFunctionalTestCase.php b/tests/Functional/Schema/SchemaManagerFunctionalTestCase.php
index a28c570861b..867798ebf6b 100644
--- a/tests/Functional/Schema/SchemaManagerFunctionalTestCase.php
+++ b/tests/Functional/Schema/SchemaManagerFunctionalTestCase.php
@@ -844,7 +844,6 @@ public function testChangeColumnsTypeWithDefaultValue(): void
         $tableDiff->fromTable                 = $table;
         $tableDiff->changedColumns['col_int'] = new ColumnDiff(
             new Column('col_int', Type::getType('integer'), ['default' => 666]),
-            ['type'],
             new Column('col_int', Type::getType('smallint'), ['default' => 666]),
         );
 
@@ -854,7 +853,6 @@ public function testChangeColumnsTypeWithDefaultValue(): void
                 'fixed' => true,
                 'default' => 'foo',
             ]),
-            ['fixed'],
             new Column('col_string', Type::getType('string'), [
                 'length' => 3,
                 'default' => 'foo',
diff --git a/tests/Platforms/AbstractMySQLPlatformTestCase.php b/tests/Platforms/AbstractMySQLPlatformTestCase.php
index 6fe0ee1e8f6..e44f8a63aa0 100644
--- a/tests/Platforms/AbstractMySQLPlatformTestCase.php
+++ b/tests/Platforms/AbstractMySQLPlatformTestCase.php
@@ -54,18 +54,6 @@ public function getGenerateTableWithMultiColumnUniqueIndexSql(): array
         ];
     }
 
-    /**
-     * {@inheritDoc}
-     */
-    public function getGenerateAlterTableSql(): array
-    {
-        return [
-            'ALTER TABLE mytable RENAME TO userlist, ADD quota INT DEFAULT NULL, DROP foo, '
-                . "CHANGE bar baz VARCHAR(255) DEFAULT 'def' NOT NULL, "
-                . 'CHANGE bloo bloo TINYINT(1) DEFAULT 0 NOT NULL',
-        ];
-    }
-
     public function testGeneratesSqlSnippets(): void
     {
         self::assertEquals('RLIKE', $this->platform->getRegexpExpression());
diff --git a/tests/Platforms/AbstractPlatformTestCase.php b/tests/Platforms/AbstractPlatformTestCase.php
index 2f7fa35b653..2dcd4913013 100644
--- a/tests/Platforms/AbstractPlatformTestCase.php
+++ b/tests/Platforms/AbstractPlatformTestCase.php
@@ -229,53 +229,6 @@ public function getGenerateConstraintForeignKeySql(ForeignKeyConstraint $fk): st
         );
     }
 
-    /** @return string[] */
-    abstract public function getGenerateAlterTableSql(): array;
-
-    public function testGeneratesTableAlterationSql(): void
-    {
-        $expectedSql = $this->getGenerateAlterTableSql();
-
-        $table = new Table('mytable');
-        $table->addColumn('id', 'integer', ['autoincrement' => true]);
-        $table->addColumn('foo', 'integer');
-        $table->addColumn('bar', 'string', ['length' => 32]);
-        $table->addColumn('bloo', 'boolean');
-        $table->setPrimaryKey(['id']);
-
-        $tableDiff                        = new TableDiff('mytable');
-        $tableDiff->fromTable             = $table;
-        $tableDiff->newName               = 'userlist';
-        $tableDiff->addedColumns['quota'] = new Column('quota', Type::getType('integer'), ['notnull' => false]);
-        $tableDiff->removedColumns['foo'] = new Column('foo', Type::getType('integer'));
-        $tableDiff->changedColumns['bar'] = new ColumnDiff(
-            new Column(
-                'baz',
-                Type::getType('string'),
-                [
-                    'length' => 255,
-                    'default' => 'def',
-                ],
-            ),
-            ['type', 'notnull', 'default'],
-            $table->getColumn('bar'),
-        );
-
-        $tableDiff->changedColumns['bloo'] = new ColumnDiff(
-            new Column(
-                'bloo',
-                Type::getType('boolean'),
-                ['default' => false],
-            ),
-            ['type', 'notnull', 'default'],
-            $table->getColumn('bloo'),
-        );
-
-        $sql = $this->platform->getAlterTableSQL($tableDiff);
-
-        self::assertEquals($expectedSql, $sql);
-    }
-
     public function testGetCustomColumnDeclarationSql(): void
     {
         self::assertEquals(
@@ -366,7 +319,6 @@ public function testGetAlterTableSqlDispatchEvent(): void
         $tableDiff->removedColumns['removed'] = new Column('removed', Type::getType('integer'), []);
         $tableDiff->changedColumns['changed'] = new ColumnDiff(
             new Column('changed2', Type::getType('string'), ['length' => 255]),
-            [],
             $table->getColumn('changed'),
         );
         $tableDiff->renamedColumns['renamed'] = new Column('renamed2', Type::getType('integer'));
@@ -617,7 +569,6 @@ public function testAlterTableChangeQuotedColumn(): void
                 Type::getType('string'),
                 ['length' => 255],
             ),
-            ['type'],
             $table->getColumn('select'),
         );
 
@@ -1131,7 +1082,6 @@ public function testQuotesTableIdentifiersInAlterTableSQL(): void
         $tableDiff->addedColumns['bloo']  = new Column('bloo', Type::getType('integer'));
         $tableDiff->changedColumns['bar'] = new ColumnDiff(
             new Column('bar', Type::getType('integer'), ['notnull' => false]),
-            ['notnull'],
             $table->getColumn('bar'),
         );
         $tableDiff->renamedColumns['id']  = new Column('war', Type::getType('integer'));
@@ -1163,7 +1113,6 @@ public function testAlterStringToFixedString(): void
                 Type::getType('string'),
                 ['fixed' => true, 'length' => 2],
             ),
-            ['fixed'],
             $table->getColumn('name'),
         );
 
diff --git a/tests/Platforms/DB2PlatformTest.php b/tests/Platforms/DB2PlatformTest.php
index d6500dd1c54..c1111d91cb5 100644
--- a/tests/Platforms/DB2PlatformTest.php
+++ b/tests/Platforms/DB2PlatformTest.php
@@ -13,6 +13,7 @@
 use Doctrine\DBAL\Schema\Table;
 use Doctrine\DBAL\Schema\TableDiff;
 use Doctrine\DBAL\Types\Type;
+use Doctrine\DBAL\Types\Types;
 
 /** @extends AbstractPlatformTestCase<DB2Platform> */
 class DB2PlatformTest extends AbstractPlatformTestCase
@@ -22,26 +23,6 @@ public function createPlatform(): AbstractPlatform
         return new DB2Platform();
     }
 
-    /**
-     * {@inheritDoc}
-     */
-    public function getGenerateAlterTableSql(): array
-    {
-        return [
-            'ALTER TABLE mytable ALTER COLUMN baz SET DATA TYPE VARCHAR(255)',
-            'ALTER TABLE mytable ALTER COLUMN baz SET NOT NULL',
-            "ALTER TABLE mytable ALTER COLUMN baz SET DEFAULT 'def'",
-            'ALTER TABLE mytable ALTER COLUMN bloo SET DATA TYPE SMALLINT',
-            'ALTER TABLE mytable ALTER COLUMN bloo SET NOT NULL',
-            'ALTER TABLE mytable ALTER COLUMN bloo SET DEFAULT 0',
-            'ALTER TABLE mytable ' .
-            'ADD COLUMN quota INTEGER DEFAULT NULL ' .
-            'DROP COLUMN foo',
-            "CALL SYSPROC.ADMIN_CMD ('REORG TABLE mytable')",
-            'RENAME TABLE mytable TO userlist',
-        ];
-    }
-
     protected function getGenerateForeignKeySql(): string
     {
         return 'ALTER TABLE test ADD FOREIGN KEY (fk_name_id) REFERENCES other_table (id)';
@@ -516,13 +497,13 @@ protected function getCommentOnColumnSQL(): array
 
     /** @dataProvider getGeneratesAlterColumnSQL */
     public function testGeneratesAlterColumnSQL(
-        string $changedProperty,
-        Column $column,
-        ?string $expectedSQLClause = null,
+        Column $oldColumn,
+        Column $newColumn,
+        ?string $expectedSQLClause,
     ): void {
         $tableDiff                        = new TableDiff('foo');
         $tableDiff->fromTable             = new Table('foo');
-        $tableDiff->changedColumns['bar'] = new ColumnDiff($column, [$changedProperty], $column);
+        $tableDiff->changedColumns['bar'] = new ColumnDiff($newColumn, $oldColumn);
 
         $expectedSQL = [];
 
@@ -540,58 +521,58 @@ public static function getGeneratesAlterColumnSQL(): iterable
     {
         return [
             [
-                'columnDefinition',
-                new Column('bar', Type::getType('decimal'), ['columnDefinition' => 'MONEY NOT NULL']),
+                new Column('bar', Type::getType(Types::DECIMAL), ['columnDefinition' => 'MONEY NULL']),
+                new Column('bar', Type::getType(Types::DECIMAL), ['columnDefinition' => 'MONEY NOT NULL']),
                 'MONEY NOT NULL',
             ],
             [
-                'type',
-                new Column('bar', Type::getType('integer')),
+                new Column('bar', Type::getType(Types::STRING)),
+                new Column('bar', Type::getType(Types::INTEGER)),
                 'SET DATA TYPE INTEGER',
             ],
             [
-                'length',
-                new Column('bar', Type::getType('string'), ['length' => 100]),
+                new Column('bar', Type::getType(Types::STRING), ['length' => 50]),
+                new Column('bar', Type::getType(Types::STRING), ['length' => 100]),
                 'SET DATA TYPE VARCHAR(100)',
             ],
             [
-                'precision',
-                new Column('bar', Type::getType('decimal'), ['precision' => 10, 'scale' => 2]),
+                new Column('bar', Type::getType(Types::DECIMAL), ['precision' => 8, 'scale' => 2]),
+                new Column('bar', Type::getType(Types::DECIMAL), ['precision' => 10, 'scale' => 2]),
                 'SET DATA TYPE NUMERIC(10, 2)',
             ],
             [
-                'scale',
-                new Column('bar', Type::getType('decimal'), ['precision' => 5, 'scale' => 4]),
+                new Column('bar', Type::getType(Types::DECIMAL), ['precision' => 5, 'scale' => 3]),
+                new Column('bar', Type::getType(Types::DECIMAL), ['precision' => 5, 'scale' => 4]),
                 'SET DATA TYPE NUMERIC(5, 4)',
             ],
             [
-                'fixed',
-                new Column('bar', Type::getType('string'), ['length' => 20, 'fixed' => true]),
+                new Column('bar', Type::getType(Types::STRING), ['length' => 10, 'fixed' => true]),
+                new Column('bar', Type::getType(Types::STRING), ['length' => 20, 'fixed' => true]),
                 'SET DATA TYPE CHAR(20)',
             ],
             [
-                'notnull',
-                new Column('bar', Type::getType('string'), ['notnull' => true]),
+                new Column('bar', Type::getType(Types::STRING), ['notnull' => false]),
+                new Column('bar', Type::getType(Types::STRING), ['notnull' => true]),
                 'SET NOT NULL',
             ],
             [
-                'notnull',
-                new Column('bar', Type::getType('string'), ['notnull' => false]),
+                new Column('bar', Type::getType(Types::STRING), ['notnull' => true]),
+                new Column('bar', Type::getType(Types::STRING), ['notnull' => false]),
                 'DROP NOT NULL',
             ],
             [
-                'default',
-                new Column('bar', Type::getType('string'), ['default' => 'foo']),
+                new Column('bar', Type::getType(Types::STRING)),
+                new Column('bar', Type::getType(Types::STRING), ['default' => 'foo']),
                 "SET DEFAULT 'foo'",
             ],
             [
-                'default',
-                new Column('bar', Type::getType('integer'), ['autoincrement' => true, 'default' => 666]),
+                new Column('bar', Type::getType(Types::INTEGER)),
+                new Column('bar', Type::getType(Types::INTEGER), ['autoincrement' => true, 'default' => 666]),
                 null,
             ],
             [
-                'default',
-                new Column('bar', Type::getType('string')),
+                new Column('bar', Type::getType(Types::STRING), ['default' => 'foo']),
+                new Column('bar', Type::getType(Types::STRING)),
                 'DROP DEFAULT',
             ],
         ];
diff --git a/tests/Platforms/OraclePlatformTest.php b/tests/Platforms/OraclePlatformTest.php
index 8527e8e0619..bd571e821c6 100644
--- a/tests/Platforms/OraclePlatformTest.php
+++ b/tests/Platforms/OraclePlatformTest.php
@@ -43,20 +43,6 @@ public function getGenerateTableWithMultiColumnUniqueIndexSql(): array
         ];
     }
 
-    /**
-     * {@inheritDoc}
-     */
-    public function getGenerateAlterTableSql(): array
-    {
-        return [
-            'ALTER TABLE mytable ADD (quota NUMBER(10) DEFAULT NULL NULL)',
-            "ALTER TABLE mytable MODIFY (baz VARCHAR2(255) DEFAULT 'def' NOT NULL, "
-                . 'bloo NUMBER(1) DEFAULT 0 NOT NULL)',
-            'ALTER TABLE mytable DROP (foo)',
-            'ALTER TABLE mytable RENAME TO userlist',
-        ];
-    }
-
     public function testRLike(): void
     {
         $this->expectException(Exception::class);
diff --git a/tests/Platforms/PostgreSQLPlatformTest.php b/tests/Platforms/PostgreSQLPlatformTest.php
index 55cfaaee176..b2b7fb0a011 100644
--- a/tests/Platforms/PostgreSQLPlatformTest.php
+++ b/tests/Platforms/PostgreSQLPlatformTest.php
@@ -43,24 +43,6 @@ public function getGenerateTableWithMultiColumnUniqueIndexSql(): array
         ];
     }
 
-    /**
-     * {@inheritDoc}
-     */
-    public function getGenerateAlterTableSql(): array
-    {
-        return [
-            'ALTER TABLE mytable ADD quota INT DEFAULT NULL',
-            'ALTER TABLE mytable DROP foo',
-            'ALTER TABLE mytable ALTER bar TYPE VARCHAR(255)',
-            "ALTER TABLE mytable ALTER bar SET DEFAULT 'def'",
-            'ALTER TABLE mytable ALTER bar SET NOT NULL',
-            'ALTER TABLE mytable ALTER bloo TYPE BOOLEAN',
-            'ALTER TABLE mytable ALTER bloo SET DEFAULT false',
-            'ALTER TABLE mytable ALTER bloo SET NOT NULL',
-            'ALTER TABLE mytable RENAME TO userlist',
-        ];
-    }
-
     public function getGenerateIndexSql(): string
     {
         return 'CREATE INDEX my_idx ON mytable (user_name, last_login)';
diff --git a/tests/Platforms/SQLServerPlatformTestCase.php b/tests/Platforms/SQLServerPlatformTestCase.php
index 80a0d2ba711..e43b670a563 100644
--- a/tests/Platforms/SQLServerPlatformTestCase.php
+++ b/tests/Platforms/SQLServerPlatformTestCase.php
@@ -50,29 +50,6 @@ public function getGenerateTableWithMultiColumnUniqueIndexSql(): array
         ];
     }
 
-    /**
-     * {@inheritDoc}
-     */
-    public function getGenerateAlterTableSql(): array
-    {
-        return [
-            'ALTER TABLE mytable ADD quota INT',
-            'ALTER TABLE mytable DROP COLUMN foo',
-            'ALTER TABLE mytable ALTER COLUMN baz NVARCHAR(255) NOT NULL',
-            "ALTER TABLE mytable ADD CONSTRAINT DF_6B2BD609_78240498 DEFAULT 'def' FOR baz",
-            'ALTER TABLE mytable ALTER COLUMN bloo BIT NOT NULL',
-            'ALTER TABLE mytable ADD CONSTRAINT DF_6B2BD609_CECED971 DEFAULT 0 FOR bloo',
-            "sp_rename 'mytable', 'userlist'",
-            "DECLARE @sql NVARCHAR(MAX) = N''; " .
-            "SELECT @sql += N'EXEC sp_rename N''' + dc.name + ''', N''' " .
-            "+ REPLACE(dc.name, '6B2BD609', 'E2B58069') + ''', ''json'';' " .
-            'FROM sys.default_constraints dc ' .
-            'JOIN sys.tables tbl ON dc.parent_object_id = tbl.object_id ' .
-            "WHERE tbl.name = 'userlist';" .
-            'EXEC sp_executesql @sql',
-        ];
-    }
-
     public function testDoesNotSupportRegexp(): void
     {
         $this->expectException(Exception::class);
@@ -682,7 +659,6 @@ public function testAlterTableWithSchemaDropColumnComments(): void
         $tableDiff                          = new TableDiff('testschema.mytable');
         $tableDiff->changedColumns['quota'] = new ColumnDiff(
             new Column('quota', Type::getType('integer'), []),
-            ['comment'],
             new Column('quota', Type::getType('integer'), ['comment' => 'A comment']),
         );
 
@@ -699,7 +675,6 @@ public function testAlterTableWithSchemaUpdateColumnComments(): void
         $tableDiff                          = new TableDiff('testschema.mytable');
         $tableDiff->changedColumns['quota'] = new ColumnDiff(
             new Column('quota', Type::getType('integer'), ['comment' => 'B comment']),
-            ['comment'],
             new Column('quota', Type::getType('integer'), ['comment' => 'A comment']),
         );
 
@@ -817,42 +792,36 @@ public function testGeneratesAlterTableSQLWithColumnComments(): void
         // Add comment to non-commented column.
         $tableDiff->changedColumns['id'] = new ColumnDiff(
             new Column('id', Type::getType('integer'), ['autoincrement' => true, 'comment' => 'primary']),
-            ['comment'],
             new Column('id', Type::getType('integer'), ['autoincrement' => true]),
         );
 
         // Change type to custom type from empty string commented column.
         $tableDiff->changedColumns['comment_empty_string'] = new ColumnDiff(
             new Column('comment_empty_string', Type::getType('json')),
-            ['type'],
             new Column('comment_empty_string', Type::getType('integer'), ['comment' => '']),
         );
 
         // Change comment to empty comment from zero-string commented column.
         $tableDiff->changedColumns['comment_string_0'] = new ColumnDiff(
             new Column('comment_string_0', Type::getType('integer'), ['comment' => '']),
-            ['comment'],
             new Column('comment_string_0', Type::getType('integer'), ['comment' => '0']),
         );
 
         // Remove comment from regular commented column.
         $tableDiff->changedColumns['comment'] = new ColumnDiff(
             new Column('comment', Type::getType('integer')),
-            ['comment'],
             new Column('comment', Type::getType('integer'), ['comment' => 'Doctrine 0wnz you!']),
         );
 
         // Change comment and change type to custom type from regular commented column.
         $tableDiff->changedColumns['`comment_quoted`'] = new ColumnDiff(
             new Column('`comment_quoted`', Type::getType('json'), ['comment' => 'Doctrine JSON.']),
-            ['comment', 'type'],
             new Column('`comment_quoted`', Type::getType('integer'), ['comment' => 'Doctrine 0wnz you!']),
         );
 
         // Remove comment and change type to custom type from regular commented column.
         $tableDiff->changedColumns['create'] = new ColumnDiff(
             new Column('create', Type::getType('json')),
-            ['comment', 'type'],
             new Column(
                 'create',
                 Type::getType('integer'),
@@ -863,21 +832,18 @@ public function testGeneratesAlterTableSQLWithColumnComments(): void
         // Add comment and change custom type to regular type from non-commented column.
         $tableDiff->changedColumns['commented_type'] = new ColumnDiff(
             new Column('commented_type', Type::getType('integer'), ['comment' => 'foo']),
-            ['comment', 'type'],
             new Column('commented_type', Type::getType('json')),
         );
 
         // Remove comment from commented custom type column.
         $tableDiff->changedColumns['commented_type_with_comment'] = new ColumnDiff(
             new Column('commented_type_with_comment', Type::getType('json')),
-            ['comment'],
             new Column('commented_type_with_comment', Type::getType('json'), ['comment' => 'Doctrine JSON type.']),
         );
 
         // Change comment from comment with string literal char column.
         $tableDiff->changedColumns['comment_with_string_literal_char'] = new ColumnDiff(
             new Column('comment_with_string_literal_char', Type::getType('string'), ['comment' => "'"]),
-            ['comment'],
             new Column('comment_with_string_literal_char', Type::getType('json'), ['comment' => "O'Reilly"]),
         );
 
@@ -1064,7 +1030,6 @@ public function testChangeColumnsTypeWithDefaultValue(): void
         $tableDiff->fromTable                 = $table;
         $tableDiff->changedColumns['col_int'] = new ColumnDiff(
             new Column('col_int', Type::getType('integer'), ['default' => 666]),
-            ['type'],
             new Column('col_int', Type::getType('smallint'), ['default' => 666]),
         );
 
@@ -1074,7 +1039,6 @@ public function testChangeColumnsTypeWithDefaultValue(): void
                 'fixed' => true,
                 'default' => 'foo',
             ]),
-            ['fixed'],
             new Column('col_string', Type::getType('string'), ['default' => 'foo']),
         );
 
@@ -1235,7 +1199,6 @@ public static function getGeneratesIdentifierNamesInAlterTableSQL(): iterable
                                 'length' => 255,
                                 'default' => 'bar',
                             ]),
-                            ['default'],
                             new Column('mycolumn', Type::getType('string'), [
                                 'length' => 255,
                                 'default' => 'foo',
@@ -1274,7 +1237,6 @@ public static function getGeneratesIdentifierNamesInAlterTableSQL(): iterable
                                 'length' => 255,
                                 'default' => 'bar',
                             ]),
-                            ['default'],
                             new Column('`mycolumn`', Type::getType('string'), [
                                 'length' => 255,
                                 'default' => 'foo',
@@ -1313,7 +1275,6 @@ public static function getGeneratesIdentifierNamesInAlterTableSQL(): iterable
                                 'length' => 255,
                                 'default' => 'bar',
                             ]),
-                            ['default'],
                             new Column('select', Type::getType('string'), [
                                 'length' => 255,
                                 'default' => 'foo',
@@ -1352,7 +1313,6 @@ public static function getGeneratesIdentifierNamesInAlterTableSQL(): iterable
                                 'length' => 255,
                                 'default' => 'bar',
                             ]),
-                            ['default'],
                             new Column('`select`', Type::getType('string'), [
                                 'length' => 255,
                                 'default' => 'foo',
@@ -1625,7 +1585,6 @@ public function testAlterTableWithSchemaSameColumnComments(): void
         $tableDiff                          = new TableDiff('testschema.mytable');
         $tableDiff->changedColumns['quota'] = new ColumnDiff(
             new Column('quota', Type::getType('integer'), ['comment' => 'A comment', 'notnull' => true]),
-            ['notnull'],
             new Column('quota', Type::getType('integer'), ['comment' => 'A comment', 'notnull' => false]),
         );
 
diff --git a/tests/Platforms/SQLitePlatformTest.php b/tests/Platforms/SQLitePlatformTest.php
index d397ebb5aa1..19074c98463 100644
--- a/tests/Platforms/SQLitePlatformTest.php
+++ b/tests/Platforms/SQLitePlatformTest.php
@@ -205,24 +205,6 @@ public function testModifyLimitQueryWithOffsetAndEmptyLimit(): void
         self::assertEquals('SELECT * FROM user LIMIT -1 OFFSET 10', $sql);
     }
 
-    /**
-     * {@inheritDoc}
-     */
-    public function getGenerateAlterTableSql(): array
-    {
-        return [
-            'CREATE TEMPORARY TABLE __temp__mytable AS SELECT id, bar, bloo FROM mytable',
-            'DROP TABLE mytable',
-            'CREATE TABLE mytable (id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, '
-                . "baz VARCHAR(255) DEFAULT 'def' NOT NULL, "
-                . 'bloo BOOLEAN DEFAULT 0 NOT NULL, '
-                . 'quota INTEGER DEFAULT NULL)',
-            'INSERT INTO mytable (id, baz, bloo) SELECT id, bar, bloo FROM __temp__mytable',
-            'DROP TABLE __temp__mytable',
-            'ALTER TABLE mytable RENAME TO userlist',
-        ];
-    }
-
     public function testGenerateTableSqlShouldNotAutoQuotePrimaryKey(): void
     {
         $table = new Table('test');
diff --git a/tests/Schema/ComparatorTest.php b/tests/Schema/ComparatorTest.php
index d11b75f9eec..9acb974c172 100644
--- a/tests/Schema/ComparatorTest.php
+++ b/tests/Schema/ComparatorTest.php
@@ -16,6 +16,7 @@
 use Doctrine\DBAL\Schema\Table;
 use Doctrine\DBAL\Schema\TableDiff;
 use Doctrine\DBAL\Types\Type;
+use Doctrine\DBAL\Types\Types;
 use PHPUnit\Framework\TestCase;
 
 use function array_keys;
@@ -104,14 +105,14 @@ public function testCompareNewTable(): void
         self::assertEquals($expected, $this->comparator->compareSchemas($schema1, $schema2));
     }
 
-    public function testCompareOnlyAutoincrementChanged(): void
+    public function testCompareAutoIncrementChanged(): void
     {
         $column1 = new Column('foo', Type::getType('integer'), ['autoincrement' => true]);
         $column2 = new Column('foo', Type::getType('integer'), ['autoincrement' => false]);
 
-        $changedProperties = $this->comparator->diffColumn($column1, $column2);
+        $diff = new ColumnDiff($column1, $column2);
 
-        self::assertEquals(['autoincrement'], $changedProperties);
+        self::assertTrue($diff->hasAutoIncrementChanged());
     }
 
     public function testCompareMissingField(): void
@@ -191,39 +192,45 @@ public function testCompareNewField(): void
 
     public function testCompareChangedColumnsChangeType(): void
     {
-        $column1 = new Column('charcolumn1', Type::getType('string'));
-        $column2 = new Column('charcolumn1', Type::getType('integer'));
+        $column1 = new Column('id', Type::getType(Types::STRING));
+        $column2 = new Column('id', Type::getType(Types::INTEGER));
 
-        self::assertEquals(['type'], $this->comparator->diffColumn($column1, $column2));
-        self::assertEquals([], $this->comparator->diffColumn($column1, $column1));
+        $diff12 = new ColumnDiff($column1, $column2);
+        self::assertTrue($diff12->hasTypeChanged());
+
+        $diff11 = new ColumnDiff($column1, $column1);
+        self::assertFalse($diff11->hasTypeChanged());
     }
 
-    public function testCompareColumnsMultipleTypeInstances(): void
+    public function testDifferentTypeInstancesOfTheSameType(): void
     {
-        $integerType1 = Type::getType('integer');
-        Type::overrideType('integer', $integerType1::class);
-        $integerType2 = Type::getType('integer');
+        $type1 = Type::getType(Types::INTEGER);
+        $type2 = clone $type1;
+
+        self::assertNotSame($type1, $type2);
 
-        $column1 = new Column('integercolumn1', $integerType1);
-        $column2 = new Column('integercolumn1', $integerType2);
+        $column1 = new Column('id', $type1);
+        $column2 = new Column('id', $type2);
 
-        self::assertEquals([], $this->comparator->diffColumn($column1, $column2));
+        $diff = new ColumnDiff($column1, $column2);
+        self::assertFalse($diff->hasTypeChanged());
     }
 
-    public function testCompareColumnsOverriddenType(): void
+    public function testOverriddenType(): void
     {
-        $oldStringInstance = Type::getType('string');
-        $integerType       = Type::getType('integer');
+        $defaultStringType = Type::getType(Types::STRING);
+        $integerType       = Type::getType(Types::INTEGER);
 
-        Type::overrideType('string', $integerType::class);
-        $overriddenStringType = Type::getType('string');
+        Type::overrideType(Types::STRING, $integerType::class);
+        $overriddenStringType = Type::getType(Types::STRING);
 
-        Type::overrideType('string', $oldStringInstance::class);
+        Type::overrideType(Types::STRING, $defaultStringType::class);
 
-        $column1 = new Column('integercolumn1', $integerType);
-        $column2 = new Column('integercolumn1', $overriddenStringType);
+        $column1 = new Column('id', $integerType);
+        $column2 = new Column('id', $overriddenStringType);
 
-        self::assertEquals([], $this->comparator->diffColumn($column1, $column2));
+        $diff = new ColumnDiff($column1, $column2);
+        self::assertFalse($diff->hasTypeChanged());
     }
 
     public function testCompareChangeColumnsMultipleNewColumnsRename(): void
@@ -802,17 +809,6 @@ public function testChangedSequence(): void
         self::assertSame($diff->changedSequences[0], $schemaNew->getSequence('baz'));
     }
 
-    /** @psalm-suppress NullArgument */
-    public function testDiffDecimalWithNullPrecision(): void
-    {
-        $column = new Column('foo', Type::getType('decimal'));
-        $column->setPrecision(null);
-
-        $column2 = new Column('foo', Type::getType('decimal'));
-
-        self::assertEquals([], $this->comparator->diffColumn($column, $column2));
-    }
-
     public function testFqnSchemaComparison(): void
     {
         $config = new SchemaConfig();
@@ -983,7 +979,6 @@ public function testCompareChangedColumn(): void
 
         $tableDiff->changedColumns['id'] = new ColumnDiff(
             $table->getColumn('id'),
-            ['type'],
             $tableFoo->getColumn('id'),
         );
 
@@ -1009,7 +1004,6 @@ public function testCompareChangedBinaryColumn(): void
 
         $tableDiff->changedColumns['id'] = new ColumnDiff(
             $table->getColumn('id'),
-            ['length', 'fixed'],
             $tableFoo->getColumn('id'),
         );
 
@@ -1038,39 +1032,6 @@ public function assertSchemaSequenceChangeCount(
         self::assertCount($removeSequenceCount, $diff->removedSequences);
     }
 
-    public function testDiffColumnPlatformOptions(): void
-    {
-        $column1 = new Column('foo', Type::getType('string'), [
-            'platformOptions' => [
-                'foo' => 'foo',
-                'bar' => 'bar',
-            ],
-        ]);
-
-        $column2 = new Column('foo', Type::getType('string'), [
-            'platformOptions' => [
-                'foo' => 'foo',
-                'foobar' => 'foobar',
-            ],
-        ]);
-
-        $column3 = new Column('foo', Type::getType('string'), [
-            'platformOptions' => [
-                'foo' => 'foo',
-                'bar' => 'rab',
-            ],
-        ]);
-
-        $column4 = new Column('foo', Type::getType('string'));
-
-        self::assertEquals([], $this->comparator->diffColumn($column1, $column2));
-        self::assertEquals([], $this->comparator->diffColumn($column2, $column1));
-        self::assertEquals(['bar'], $this->comparator->diffColumn($column1, $column3));
-        self::assertEquals(['bar'], $this->comparator->diffColumn($column3, $column1));
-        self::assertEquals([], $this->comparator->diffColumn($column1, $column4));
-        self::assertEquals([], $this->comparator->diffColumn($column4, $column1));
-    }
-
     public function testComparesNamespaces(): void
     {
         $fromSchema = $this->getMockBuilder(Schema::class)
@@ -1104,34 +1065,17 @@ public function testComparesNamespaces(): void
         self::assertEquals($expected, $this->comparator->compareSchemas($fromSchema, $toSchema));
     }
 
-    public function testCompareGuidColumns(): void
-    {
-        $column1 = new Column('foo', Type::getType('guid'), ['comment' => 'GUID 1']);
-        $column2 = new Column(
-            'foo',
-            Type::getType('guid'),
-            ['notnull' => false, 'length' => 36, 'fixed' => true, 'default' => 'NEWID()', 'comment' => 'GUID 2.'],
-        );
-
-        self::assertEquals(['notnull', 'default', 'comment'], $this->comparator->diffColumn($column1, $column2));
-        self::assertEquals(['notnull', 'default', 'comment'], $this->comparator->diffColumn($column2, $column1));
-    }
-
     /** @dataProvider getCompareColumnComments */
     public function testCompareColumnComments(string $comment1, string $comment2, bool $equals): void
     {
         $column1 = new Column('foo', Type::getType('integer'), ['comment' => $comment1]);
         $column2 = new Column('foo', Type::getType('integer'), ['comment' => $comment2]);
 
-        $expectedDiff = $equals ? [] : ['comment'];
-
-        $actualDiff = $this->comparator->diffColumn($column1, $column2);
-
-        self::assertSame($expectedDiff, $actualDiff);
-
-        $actualDiff = $this->comparator->diffColumn($column2, $column1);
+        $diff1 = new ColumnDiff($column1, $column2);
+        $diff2 = new ColumnDiff($column2, $column1);
 
-        self::assertSame($expectedDiff, $actualDiff);
+        self::assertSame(! $equals, $diff1->hasCommentChanged());
+        self::assertSame(! $equals, $diff2->hasCommentChanged());
     }
 
     /** @return mixed[][] */