Auto-generate foreign key constraint names when not provided

src/Db/Adapter/MysqlAdapter.php

@@ -29,6 +29,11 @@
  */
 class MysqlAdapter extends AbstractAdapter
 {
+    /**
+     * Maximum length for identifiers (table names, column names, constraint names, etc.)
+     */
+    protected const IDENTIFIER_MAX_LENGTH = 64;
+
     /**
      * @var string[]
      */
@@ -977,7 +982,7 @@ protected function getAddForeignKeyInstructions(TableMetadata $table, ForeignKey
     {
         $alter = sprintf(
             'ADD %s',
-            $this->getForeignKeySqlDefinition($foreignKey),
+            $this->getForeignKeySqlDefinition($foreignKey, $table->getName()),
         );
 
         return new AlterInstructions([$alter]);
@@ -1192,14 +1197,13 @@ protected function getIndexSqlDefinition(Index $index): string
      * Gets the MySQL Foreign Key Definition for an ForeignKey object.
      *
      * @param \Migrations\Db\Table\ForeignKey $foreignKey Foreign key
+     * @param string $tableName Table name for auto-generating constraint name
      * @return string
      */
-    protected function getForeignKeySqlDefinition(ForeignKey $foreignKey): string
+    protected function getForeignKeySqlDefinition(ForeignKey $foreignKey, string $tableName): string
     {
-        $def = '';
-        if ($foreignKey->getName()) {
-            $def .= ' CONSTRAINT ' . $this->quoteColumnName((string)$foreignKey->getName());
-        }
+        $constraintName = $foreignKey->getName() ?: $this->getUniqueForeignKeyName($tableName, $foreignKey->getColumns());
+        $def = ' CONSTRAINT ' . $this->quoteColumnName($constraintName);
         $columnNames = [];
         foreach ($foreignKey->getColumns() as $column) {
             $columnNames[] = $this->quoteColumnName($column);
@@ -1222,6 +1226,35 @@ protected function getForeignKeySqlDefinition(ForeignKey $foreignKey): string
         return $def;
     }
 
+    /**
+     * Generate a unique foreign key constraint name.
+     *
+     * @param string $tableName Table name
+     * @param array<string> $columns Column names
+     * @return string
+     */
+    protected function getUniqueForeignKeyName(string $tableName, array $columns): string
+    {
+        $baseName = $tableName . '_' . implode('_', $columns);
+        $maxLength = static::IDENTIFIER_MAX_LENGTH - 3;
+        if (strlen($baseName) > $maxLength) {
+            $baseName = substr($baseName, 0, $maxLength);
+        }
+        $existingKeys = $this->getForeignKeys($tableName);
+        $existingNames = array_column($existingKeys, 'name');
+
+        if (!in_array($baseName, $existingNames, true)) {
+            return $baseName;
+        }
+
+        $counter = 2;
+        while (in_array($baseName . '_' . $counter, $existingNames, true)) {
+            $counter++;
+        }
+
+        return $baseName . '_' . $counter;
+    }
+
     /**
      * Returns MySQL column types (inherited and MySQL specified).
      *

src/Db/Adapter/PostgresAdapter.php

@@ -27,6 +27,11 @@
 
 class PostgresAdapter extends AbstractAdapter
 {
+    /**
+     * Maximum length for identifiers (table names, column names, constraint names, etc.)
+     */
+    protected const IDENTIFIER_MAX_LENGTH = 63;
+
     public const GENERATED_ALWAYS = 'ALWAYS';
     public const GENERATED_BY_DEFAULT = 'BY DEFAULT';
     /**
@@ -949,11 +954,7 @@ protected function getIndexSqlDefinition(Index $index, string $tableName): strin
      */
     protected function getForeignKeySqlDefinition(ForeignKey $foreignKey, string $tableName): string
     {
-        $parts = $this->getSchemaName($tableName);
-
-        $constraintName = $foreignKey->getName() ?: (
-            $parts['table'] . '_' . implode('_', $foreignKey->getColumns()) . '_fkey'
-        );
+        $constraintName = $foreignKey->getName() ?: $this->getUniqueForeignKeyName($tableName, $foreignKey->getColumns());
         $columnList = implode(', ', array_map($this->quoteColumnName(...), $foreignKey->getColumns()));
         $refColumnList = implode(', ', array_map($this->quoteColumnName(...), $foreignKey->getReferencedColumns()));
         $def = ' CONSTRAINT ' . $this->quoteColumnName($constraintName) .
@@ -972,6 +973,36 @@ protected function getForeignKeySqlDefinition(ForeignKey $foreignKey, string $ta
         return $def;
     }
 
+    /**
+     * Generate a unique foreign key constraint name.
+     *
+     * @param string $tableName Table name
+     * @param array<string> $columns Column names
+     * @return string
+     */
+    protected function getUniqueForeignKeyName(string $tableName, array $columns): string
+    {
+        $parts = $this->getSchemaName($tableName);
+        $baseName = $parts['table'] . '_' . implode('_', $columns) . '_fkey';
+        $maxLength = static::IDENTIFIER_MAX_LENGTH - 3;
+        if (strlen($baseName) > $maxLength) {
+            $baseName = substr($baseName, 0, $maxLength);
+        }
+        $existingKeys = $this->getForeignKeys($tableName);
+        $existingNames = array_column($existingKeys, 'name');
+
+        if (!in_array($baseName, $existingNames, true)) {
+            return $baseName;
+        }
+
+        $counter = 2;
+        while (in_array($baseName . '_' . $counter, $existingNames, true)) {
+            $counter++;
+        }
+
+        return $baseName . '_' . $counter;
+    }
+
     /**
      * @inheritDoc
      */

src/Db/Adapter/SqliteAdapter.php

@@ -1425,7 +1425,7 @@ protected function getAddForeignKeyInstructions(TableMetadata $table, ForeignKey
         $tableName = $table->getName();
         $instructions->addPostStep(function ($state) use ($foreignKey, $tableName) {
             $this->execute('pragma foreign_keys = ON');
-            $sql = substr($state['createSQL'], 0, -1) . ',' . $this->getForeignKeySqlDefinition($foreignKey) . '); ';
+            $sql = substr($state['createSQL'], 0, -1) . ',' . $this->getForeignKeySqlDefinition($foreignKey, $tableName) . '); ';
 
             //Delete indexes from original table and recreate them in temporary table
             $schema = $this->getSchemaName($tableName, true)['schema'];
@@ -1670,14 +1670,13 @@ public function getColumnTypes(): array
      * Gets the SQLite Foreign Key Definition for an ForeignKey object.
      *
      * @param \Migrations\Db\Table\ForeignKey $foreignKey Foreign key
+     * @param string $tableName Table name for auto-generating constraint name
      * @return string
      */
-    protected function getForeignKeySqlDefinition(ForeignKey $foreignKey): string
+    protected function getForeignKeySqlDefinition(ForeignKey $foreignKey, string $tableName): string
     {
-        $def = '';
-        if ($foreignKey->getName()) {
-            $def .= ' CONSTRAINT ' . $this->quoteColumnName((string)$foreignKey->getName());
-        }
+        $constraintName = $foreignKey->getName() ?: $this->getUniqueForeignKeyName($tableName, $foreignKey->getColumns());
+        $def = ' CONSTRAINT ' . $this->quoteColumnName($constraintName);
         $columnNames = [];
         foreach ($foreignKey->getColumns() as $column) {
             $columnNames[] = $this->quoteColumnName($column);
@@ -1698,6 +1697,31 @@ protected function getForeignKeySqlDefinition(ForeignKey $foreignKey): string
         return $def;
     }
 
+    /**
+     * Generate a unique foreign key constraint name.
+     *
+     * @param string $tableName Table name
+     * @param array<string> $columns Column names
+     * @return string
+     */
+    protected function getUniqueForeignKeyName(string $tableName, array $columns): string
+    {
+        $baseName = $tableName . '_' . implode('_', $columns);
+        $existingKeys = $this->getForeignKeys($tableName);
+        $existingNames = array_column($existingKeys, 'name');
+
+        if (!in_array($baseName, $existingNames, true)) {
+            return $baseName;
+        }
+
+        $counter = 2;
+        while (in_array($baseName . '_' . $counter, $existingNames, true)) {
+            $counter++;
+        }
+
+        return $baseName . '_' . $counter;
+    }
+
     /**
      * @inheritDoc
      */

src/Db/Adapter/SqlserverAdapter.php

@@ -28,6 +28,11 @@
  */
 class SqlserverAdapter extends AbstractAdapter
 {
+    /**
+     * Maximum length for identifiers (table names, column names, constraint names, etc.)
+     */
+    protected const IDENTIFIER_MAX_LENGTH = 128;
+
     /**
      * @var string[]
      */
@@ -864,7 +869,7 @@ protected function getIndexSqlDefinition(Index $index, string $tableName): strin
      */
     protected function getForeignKeySqlDefinition(ForeignKey $foreignKey, string $tableName): string
     {
-        $constraintName = $foreignKey->getName() ?: $tableName . '_' . implode('_', $foreignKey->getColumns());
+        $constraintName = $foreignKey->getName() ?: $this->getUniqueForeignKeyName($tableName, $foreignKey->getColumns());
         $columnList = implode(', ', array_map($this->quoteColumnName(...), $foreignKey->getColumns()));
         $refColumnList = implode(', ', array_map($this->quoteColumnName(...), $foreignKey->getReferencedColumns()));
 
@@ -881,6 +886,35 @@ protected function getForeignKeySqlDefinition(ForeignKey $foreignKey, string $ta
         return $def;
     }
 
+    /**
+     * Generate a unique foreign key constraint name.
+     *
+     * @param string $tableName Table name
+     * @param array<string> $columns Column names
+     * @return string
+     */
+    protected function getUniqueForeignKeyName(string $tableName, array $columns): string
+    {
+        $baseName = $tableName . '_' . implode('_', $columns);
+        $maxLength = static::IDENTIFIER_MAX_LENGTH - 3;
+        if (strlen($baseName) > $maxLength) {
+            $baseName = substr($baseName, 0, $maxLength);
+        }
+        $existingKeys = $this->getForeignKeys($tableName);
+        $existingNames = array_column($existingKeys, 'name');
+
+        if (!in_array($baseName, $existingNames, true)) {
+            return $baseName;
+        }
+
+        $counter = 2;
+        while (in_array($baseName . '_' . $counter, $existingNames, true)) {
+            $counter++;
+        }
+
+        return $baseName . '_' . $counter;
+    }
+
     /**
      * Creates the specified schema.
      *

tests/comparisons/Diff/default/the_diff_default_mysql.php

@@ -16,7 +16,7 @@ class TheDiffDefaultMysql extends BaseMigration
     public function up(): void
     {
         $this->table('articles')
-            ->dropForeignKey([], 'articles_ibfk_1')
+            ->dropForeignKey([], 'articles_user_id')
             ->removeIndexByName('UNIQUE_SLUG')
             ->removeIndexByName('rating_index')
             ->removeIndexByName('BY_NAME')
@@ -86,7 +86,7 @@ public function up(): void
             ])
             ->addIndex(
                 $this->index('user_id')
-                    ->setName('categories_ibfk_1')
+                    ->setName('categories_user_id')
             )
             ->addIndex(
                 $this->index('name')
@@ -101,7 +101,7 @@ public function up(): void
                     ->setReferencedColumns('id')
                     ->setDelete('RESTRICT')
                     ->setUpdate('RESTRICT')
-                    ->setName('categories_ibfk_1')
+                    ->setName('categories_user_id')
             )
             ->update();
 
@@ -234,7 +234,7 @@ public function down(): void
                     ->setReferencedColumns('id')
                     ->setDelete('CASCADE')
                     ->setUpdate('CASCADE')
-                    ->setName('articles_ibfk_1')
+                    ->setName('articles_user_id')
             )
             ->update();
 

tests/comparisons/Diff/simple/the_diff_simple_mysql.php

@@ -72,7 +72,7 @@ public function up(): void
                     ->setReferencedColumns('id')
                     ->setDelete('RESTRICT')
                     ->setUpdate('RESTRICT')
-                    ->setName('articles_ibfk_1')
+                    ->setName('articles_user_id')
             )
             ->update();
     }