fix: Forge::modifyColumn() for Postgre handler

system/Database/Postgre/Forge.php

@@ -109,7 +109,7 @@ protected function _alterTable(string $alterType, string $table, $processedField
 
             if (! empty($field['default'])) {
                 $sqls[] = $sql . ' ALTER COLUMN ' . $this->db->escapeIdentifiers($field['name'])
-                    . " SET DEFAULT {$field['default']}";
+                    . " SET {$field['default']}";
             }
 
             $nullable = true; // Nullable by default.

system/Database/SQLSRV/Forge.php

@@ -253,8 +253,27 @@ protected function _alterTable(string $alterType, string $table, $processedField
             }
 
             if (! empty($field['default'])) {
-                $sqls[] = $sql . ' ALTER COLUMN ADD CONSTRAINT ' . $this->db->escapeIdentifiers($field['name']) . '_def'
-                    . " DEFAULT {$field['default']} FOR " . $this->db->escapeIdentifiers($field['name']);
+                $fullTable = $this->db->escapeIdentifiers($this->db->schema) . '.' . $this->db->escapeIdentifiers($table);
+                $colName   = $field['name']; // bare, for sys.columns lookup
+
+                // find the existing default constraint name for this column
+                $findSql = <<<SQL
+                    SELECT dc.name AS constraint_name
+                    FROM sys.default_constraints dc
+                    JOIN sys.columns c
+                        ON dc.parent_object_id = c.object_id
+                        AND dc.parent_column_id = c.column_id
+                    WHERE dc.parent_object_id = OBJECT_ID(N'{$fullTable}')
+                        AND c.name = N'{$colName}';
+                    SQL;
+
+                $toDrop = $this->db->query($findSql)->getRowArray();
+                if (isset($toDrop['constraint_name']) && $toDrop['constraint_name'] !== '') {
+                    $sqls[] = $sql . ' DROP CONSTRAINT ' . $this->db->escapeIdentifiers($toDrop['constraint_name']);
+                }
+
+                $sqls[] = $sql . ' ADD CONSTRAINT ' . $this->db->escapeIdentifiers($field['name'] . '_def')
+                    . "{$field['default']} FOR " . $this->db->escapeIdentifiers($field['name']);
             }
 
             $nullable = true; // Nullable by default.

tests/system/Database/Live/ForgeTest.php

@@ -1818,6 +1818,28 @@ public function testProcessIndexesWithForeignKeyOnly(): void
         $this->forge->dropTable('user2', true);
     }
 
+    public function testChangeDefaultFieldValueWithModifyColumn(): void
+    {
+        $this->forge->addField([
+            'delivery_sum'      => ['type' => 'int', 'constraint' => 6, 'default' => 10],
+            'delivery_free_sum' => ['type' => 'int', 'constraint' => 6, 'default' => 10],
+        ])->addKey('id', true)->createTable('test_stores', true);
+
+        $this->forge->modifyColumn('test_stores', [
+            'delivery_sum'      => ['type' => 'int', 'constraint' => 6, 'default' => 100],
+            'delivery_free_sum' => ['type' => 'int', 'constraint' => 6, 'default' => 1000],
+        ]);
+
+        $expected = ['delivery_sum' => '100', 'delivery_free_sum' => '1000'];
+
+        $fields  = $this->db->getFieldData('test_stores');
+        $results = array_column($fields, 'default', 'name');
+
+        $this->assertSame($expected, $results);
+
+        $this->forge->dropTable('test_stores', true);
+    }
+
     private function createUser2TableWithKeys(): void
     {
         $fields = [

user_guide_src/source/changelogs/v4.6.4.rst

@@ -32,6 +32,7 @@ Bugs Fixed
 
 - **Database:** Fixed a bug in ``Database::connect()`` which was causing to store non-shared connection instances in shared cache.
 - **Database:** Fixed a bug in ``Connection::getFieldData()`` for ``SQLSRV`` and ``OCI8`` where extra characters were returned in column default values (specific to those handlers), instead of following the convention used by other drivers.
+- **Forge:** Fixed a bug in ``Postgre`` and ``SQLSRV`` where changing a column's default value using ``Forge::modifyColumn()`` method produced incorrect SQL syntax.
 
 See the repo's
 `CHANGELOG.md <https://github.com/codeigniter4/CodeIgniter4/blob/develop/CHANGELOG.md>`_

utils/phpstan-baseline/loader.neon

@@ -1,4 +1,4 @@
-# total 2836 errors
+# total 2837 errors
 includes:
     - argument.type.neon
     - assign.propertyType.neon

utils/phpstan-baseline/property.notFound.neon

@@ -1,4 +1,4 @@
-# total 58 errors
+# total 59 errors
 
 parameters:
     ignoreErrors:
@@ -14,7 +14,7 @@ parameters:
 
         -
             message: '#^Access to an undefined property CodeIgniter\\Database\\BaseConnection\:\:\$schema\.$#'
-            count: 13
+            count: 14
             path: ../../system/Database/SQLSRV/Forge.php
 
         -