Alter table LOCK=SHARED

src/Database/Adapter.php

@@ -31,6 +31,8 @@ abstract class Adapter
 
     protected int $inTransaction = 0;
 
+    protected bool $alterLocks = false;
+
     /**
      * @var array<string, mixed>
      */
@@ -1434,4 +1436,25 @@ abstract public function setSupportForAttributes(bool $support): bool;
      */
     abstract public function getSupportForIntegerBooleans(): bool;
 
+    /**
+     * Does the adapter have support for ALTER TABLE locking modes?
+     *
+     * When enabled, adapters can specify lock behavior (e.g., LOCK=SHARED)
+     * during ALTER TABLE operations to control concurrent access.
+     *
+     * @return bool
+     */
+    abstract public function getSupportForAlterLocks(): bool;
+
+    /**
+     * @param bool $enable
+     *
+     * @return $this
+     */
+    public function enableAlterLocks(bool $enable): self
+    {
+        $this->alterLocks = $enable;
+
+        return $this;
+    }
 }

src/Database/Adapter/MariaDB.php

@@ -2220,4 +2220,9 @@ public function getSupportForOptionalSpatialAttributeWithExistingRows(): bool
     {
         return true;
     }
+
+    public function getSupportForAlterLocks(): bool
+    {
+        return true;
+    }
 }

src/Database/Adapter/Mongo.php

@@ -3211,4 +3211,9 @@ public function getTenantQuery(string $collection, string $alias = ''): string
     {
         return '';
     }
+
+    public function getSupportForAlterLocks(): bool
+    {
+        return false;
+    }
 }

src/Database/Adapter/Pool.php

@@ -632,4 +632,9 @@ public function setAuthorization(Authorization $authorization): self
         $this->authorization = $authorization;
         return $this;
     }
+
+    public function getSupportForAlterLocks(): bool
+    {
+        return $this->delegate(__FUNCTION__, \func_get_args());
+    }
 }

src/Database/Adapter/SQL.php

@@ -247,7 +247,7 @@ public function createAttribute(string $collection, string $id, string $type, in
     {
         $id = $this->quote($this->filter($id));
         $type = $this->getSQLType($type, $size, $signed, $array, $required);
-        $sql = "ALTER TABLE {$this->getSQLTable($collection)} ADD COLUMN {$id} {$type};";
+        $sql = "ALTER TABLE {$this->getSQLTable($collection)} ADD COLUMN {$id} {$type} {$this->getLockType()};";
         $sql = $this->trigger(Database::EVENT_ATTRIBUTE_CREATE, $sql);
 
         try {
@@ -284,7 +284,7 @@ public function createAttributes(string $collection, array $attributes): bool
 
         $columns = \implode(', ADD COLUMN ', $parts);
 
-        $sql = "ALTER TABLE {$this->getSQLTable($collection)} ADD COLUMN {$columns};";
+        $sql = "ALTER TABLE {$this->getSQLTable($collection)} ADD COLUMN {$columns} {$this->getLockType()};";
         $sql = $this->trigger(Database::EVENT_ATTRIBUTE_CREATE, $sql);
 
         try {
@@ -3514,4 +3514,18 @@ public function setSupportForAttributes(bool $support): bool
     {
         return true;
     }
+
+    public function getSupportForAlterLocks(): bool
+    {
+        return false;
+    }
+
+    public function getLockType(): string
+    {
+        if ($this->getSupportForAlterLocks() && $this->alterLocks) {
+            return ',LOCK=SHARED';
+        }
+
+        return '';
+    }
 }

src/Database/Adapter/SQLite.php

@@ -1866,4 +1866,9 @@ public function getUpsertStatement(
 
         return $stmt;
     }
+
+    public function getSupportForAlterLocks(): bool
+    {
+        return false;
+    }
 }

src/Database/Database.php

@@ -1218,6 +1218,23 @@ public function getTenantPerDocument(): bool
         return $this->adapter->getTenantPerDocument();
     }
 
+    /**
+     * Enable or disable LOCK=SHARED during ALTER TABLE operation
+     *
+     * Set lock mode when altering tables
+     *
+     * @param bool $enabled
+     * @return static
+     */
+    public function enableLocks(bool $enabled): static
+    {
+        if ($this->adapter->getSupportForAlterLocks()) {
+            $this->adapter->enableAlterLocks($enabled);
+        }
+
+        return $this;
+    }
+
     public function getPreserveDates(): bool
     {
         return $this->preserveDates;

tests/e2e/Adapter/SharedTables/MariaDBTest.php

@@ -53,7 +53,9 @@ public function getDatabase(bool $fresh = false): Database
             ->setDatabase('utopiaTests')
             ->setSharedTables(true)
             ->setTenant(999)
-            ->setNamespace(static::$namespace = '');
+            ->setNamespace(static::$namespace = '')
+            ->enableLocks(true)
+        ;
 
         if ($database->exists()) {
             $database->delete();

tests/e2e/Adapter/SharedTables/MySQLTest.php

@@ -55,7 +55,9 @@ public function getDatabase(): Database
             ->setDatabase('utopiaTests')
             ->setSharedTables(true)
             ->setTenant(999)
-            ->setNamespace(static::$namespace = '');
+            ->setNamespace(static::$namespace = '')
+            ->enableLocks(true)
+        ;
 
         if ($database->exists()) {
             $database->delete();