Added named window expression support

src/Database/Expression/AggregateExpression.php

@@ -33,17 +33,18 @@ class AggregateExpression extends FunctionExpression implements WindowInterface
     protected $window;
 
     /**
-     * Adds an empty `OVER()` window expression.
+     * Adds an empty `OVER()` window expression or a named window epression.
      *
-     * If the window expression for this aggregate is already
-     * initialized, this does nothing.
+     * Does nothing if the window expression for this aggregate is already
+     * initialized
      *
+     * @param string|null $name Window name
      * @return $this
      */
-    public function over()
+    public function over(?string $name = null)
     {
         if ($this->window === null) {
-            $this->window = new WindowExpression();
+            $this->window = new WindowExpression($name);
         }
 
         return $this;
@@ -176,7 +177,11 @@ public function sql(ValueBinder $generator): string
     {
         $sql = parent::sql($generator);
         if ($this->window !== null) {
-            $sql .= ' ' . $this->window->sql($generator);
+            if ($this->window->isEmpty() && $this->window->getName()) {
+                $sql .= ' OVER ' . $this->window->getName();
+            } else {
+                $sql .= ' OVER (' . $this->window->sql($generator) . ')';
+            }
         }
 
         return $sql;

src/Database/Expression/WindowExpression.php

@@ -26,6 +26,11 @@
  */
 class WindowExpression implements ExpressionInterface, WindowInterface
 {
+    /**
+     * @var string|null
+     */
+    protected $name;
+
     /**
      * @var \Cake\Database\ExpressionInterface[]
      */
@@ -46,6 +51,49 @@ class WindowExpression implements ExpressionInterface, WindowInterface
      */
     protected $exclusion;
 
+    /**
+     * @param string|null $name Window name
+     */
+    public function __construct(?string $name = null)
+    {
+        $this->name = $name;
+    }
+
+    /**
+     * Return whether window expression is empty.
+     *
+     * An expression is empty if it has no partition, order or frame clauses.
+     *
+     * @return bool
+     */
+    public function isEmpty(): bool
+    {
+        return !$this->partitions && !$this->frame && !$this->order;
+    }
+
+    /**
+     * Return named window used in this expresion if set.
+     *
+     * @return string|null
+     */
+    public function getName(): ?string
+    {
+        return $this->name;
+    }
+
+    /**
+     * Sets the window name.
+     *
+     * @param string $name Window name
+     * @return $this
+     */
+    public function setName(string $name)
+    {
+        $this->name = $name;
+
+        return $this;
+    }
+
     /**
      * @inheritDoc
      */
@@ -192,6 +240,10 @@ public function excludeTies()
      */
     public function sql(ValueBinder $generator): string
     {
+        if ($this->isEmpty()) {
+            return '';
+        }
+
         $partitionSql = '';
         if ($this->partitions) {
             $expressions = [];
@@ -202,7 +254,7 @@ public function sql(ValueBinder $generator): string
             $partitionSql = 'PARTITION BY ' . implode(', ', $expressions);
         }
 
-        $orderSql = $this->order ? $orderSql = $this->order->sql($generator) : '';
+        $orderSql = $this->order ? $this->order->sql($generator) : '';
 
         $frameSql = '';
         if ($this->frame) {
@@ -234,8 +286,11 @@ public function sql(ValueBinder $generator): string
             }
         }
 
+        $name = $this->name ? $this->name . ' ' : '';
+
         return sprintf(
-            'OVER (%s%s%s%s%s)',
+            '%s%s%s%s%s%s',
+            $name,
             $partitionSql,
             $partitionSql && $orderSql ? ' ' : '',
             $orderSql,

src/Database/Query.php

@@ -21,6 +21,7 @@
 use Cake\Database\Expression\OrderClauseExpression;
 use Cake\Database\Expression\QueryExpression;
 use Cake\Database\Expression\ValuesExpression;
+use Cake\Database\Expression\WindowExpression;
 use Cake\Database\Statement\CallbackStatement;
 use Closure;
 use InvalidArgumentException;
@@ -85,6 +86,7 @@ class Query implements ExpressionInterface, IteratorAggregate
         'where' => null,
         'group' => [],
         'having' => null,
+        'window' => [],
         'order' => null,
         'limit' => null,
         'offset' => null,
@@ -1328,6 +1330,32 @@ public function andHaving($conditions, $types = [])
         return $this;
     }
 
+    /**
+     * Adds a named window expression.
+     *
+     * Users are responsible for adding windows in the order each database requires.
+     *
+     * @param string $name Window name
+     * @param \Cake\Database\Expression\WindowExpression|\Closure $window Window expression
+     * @param bool $overwrite Clear all previous query window expressions
+     * @return $this
+     */
+    public function window(string $name, $window, bool $overwrite = false)
+    {
+        if ($overwrite) {
+            $this->_parts['window'] = [];
+        }
+
+        if ($window instanceof Closure) {
+            $window = $window(new WindowExpression(), $this);
+        }
+
+        $this->_parts['window'][] = ['name' => $name, 'window' => $window];
+        $this->_dirty();
+
+        return $this;
+    }
+
     /**
      * Set the page of results you want.
      *

src/Database/QueryCompiler.php

@@ -51,7 +51,7 @@ class QueryCompiler
      * @var array
      */
     protected $_selectParts = [
-        'select', 'from', 'join', 'where', 'group', 'having', 'order', 'limit',
+        'select', 'from', 'join', 'where', 'group', 'having', 'window', 'order', 'limit',
         'offset', 'union', 'epilog',
     ];
 
@@ -270,6 +270,29 @@ protected function _buildJoinPart(array $parts, Query $query, ValueBinder $gener
         return $joins;
     }
 
+    /**
+     * Helper function to build the string representation of a window clause.
+     *
+     * @param array $parts List of windows to be transformed to string
+     * @param \Cake\Database\Query $query The query that is being compiled
+     * @param \Cake\Database\ValueBinder $generator the placeholder generator to be used in expressions
+     * @return string
+     */
+    protected function _buildWindowPart(array $parts, Query $query, ValueBinder $generator): string
+    {
+        $windows = [];
+        foreach ($parts as $window) {
+            $expr = $window['window'];
+            if ($expr->isEmpty() && $expr->getName()) {
+                $windows[] = $window['name'] . ' AS (' . $expr->getName() . ')';
+            } else {
+                $windows[] = $window['name'] . ' AS (' . $expr->sql($generator) . ')';
+            }
+        }
+
+        return ' WINDOW ' . implode(', ', $windows);
+    }
+
     /**
      * Helper function to generate SQL for SET expressions.
      *

src/Database/SqlserverCompiler.php

@@ -49,7 +49,7 @@ class SqlserverCompiler extends QueryCompiler
      * @inheritDoc
      */
     protected $_selectParts = [
-        'select', 'from', 'join', 'where', 'group', 'having', 'order', 'offset',
+        'select', 'from', 'join', 'where', 'group', 'having', 'window', 'order', 'offset',
         'limit', 'union', 'epilog',
     ];
 

tests/TestCase/Database/Expression/AggregateExpressionTest.php

@@ -37,6 +37,12 @@ public function testEmptyWindow()
     {
         $f = (new AggregateExpression('MyFunction'))->over();
         $this->assertSame('MyFunction() OVER ()', $f->sql(new ValueBinder()));
+
+        $f = (new AggregateExpression('MyFunction'))->over('name');
+        $this->assertEqualsSql(
+            'MyFunction() OVER name',
+            $f->sql(new ValueBinder())
+        );
     }
 
     /**