picodb(mssql): teach picodb to use TOP for limits on MSSQL

libs/picodb/lib/PicoDb/Driver/Base.php

@@ -30,6 +30,14 @@ abstract class Base
      */
     protected $pdo = null;
 
+    /**
+     * use TOP or LIMIT for returning a subset of rows
+     *
+     * @access public
+     * @var bool
+     */
+    public bool $useTop;
+
     /**
      * Create a new PDO connection
      *
@@ -128,6 +136,7 @@ abstract class Base
 
         $this->createConnection($settings);
         $this->pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
+        $this->useTop = false;
     }
 
     /**
@@ -231,4 +240,5 @@ abstract class Base
     {
         return $this->getConnection()->query('SELECT VERSION()')->fetchColumn();
     }
+
 }

libs/picodb/lib/PicoDb/Driver/Mssql.php

@@ -25,6 +25,18 @@ class Mssql extends Base
         'database',
     );
 
+    /**
+     * Constructor
+     *
+     * @access public
+     * @param  array   $settings
+     */
+    public function __construct(array $settings)
+    {
+        parent::__construct($settings);
+        $this->useTop = true;
+    }
+
     /**
      * Table to store the schema version
      *
@@ -180,4 +192,5 @@ class Mssql extends Base
         $this->getConnection()->exec('SET SHOWPLAN_ALL ON');
         return $this->getConnection()->query($this->getSqlFromPreparedStatement($sql, $values))->fetchAll(PDO::FETCH_ASSOC);
     }
+
 }

libs/picodb/lib/PicoDb/Table.php

@@ -119,6 +119,14 @@ class Table
      */
     private $sqlSelect = '';
 
+    /**
+     * SQL TOP clause
+     *
+     * @access private
+     * @var    string
+     */
+    private $sqlTop = '';
+
     /**
      * SQL joins
      *
@@ -578,7 +586,11 @@ class Table
     public function limit($value)
     {
         if (! is_null($value)) {
-            $this->sqlLimit = ' LIMIT '.(int) $value;
+            if ($this->db->getDriver()->useTop) {
+                $this->sqlTop = ' TOP ('.(int) $value.') ';
+            } else {
+                $this->sqlLimit = ' LIMIT '.(int) $value;
+            }
         }
 
         return $this;
@@ -693,7 +705,8 @@ class Table
         $this->groupBy = $this->db->escapeIdentifierList($this->groupBy);
 
         return trim(sprintf(
-            'SELECT %s FROM %s %s %s %s %s %s %s',
+            'SELECT %s %s FROM %s %s %s %s %s %s %s',
+            $this->sqlTop,
             $this->sqlSelect,
             $this->db->escapeIdentifier($this->name),
             implode(' ', $this->joins),