feat(postgrest): add missing PostgREST v12 operators

Adds three missing operators from PostgREST v12 specification:
- matchRegex: PostgreSQL regex matching (~) - case sensitive
- imatchRegex: PostgreSQL regex matching (~*) - case insensitive
- isDistinct: IS DISTINCT FROM - treats NULL as comparable value

All existing operators were reviewed and verified against v12 docs.
Tests added for all new operators.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: grdsdev

packages/postgrest/lib/src/postgrest_filter_builder.dart

@@ -476,6 +476,45 @@ class PostgrestFilterBuilder<T> extends PostgrestTransformBuilder<T> {
     return copyWithUrl(url);
   }
 
+  /// Finds all rows whose value in the stated [column] matches the supplied [pattern] using PostgreSQL regular expression (case sensitive).
+  ///
+  /// ```dart
+  /// await supabase
+  ///     .from('users')
+  ///     .select()
+  ///     .matchRegex('username', '^sup.*');
+  /// ```
+  PostgrestFilterBuilder<T> matchRegex(String column, String pattern) {
+    return copyWithUrl(appendSearchParams(column, 'match.$pattern'));
+  }
+
+  /// Finds all rows whose value in the stated [column] matches the supplied [pattern] using PostgreSQL regular expression (case insensitive).
+  ///
+  /// ```dart
+  /// await supabase
+  ///     .from('users')
+  ///     .select()
+  ///     .imatchRegex('username', '^SUP.*');
+  /// ```
+  PostgrestFilterBuilder<T> imatchRegex(String column, String pattern) {
+    return copyWithUrl(appendSearchParams(column, 'imatch.$pattern'));
+  }
+
+  /// Finds all rows whose value on the stated [column] is not equal to the specified [value], treating `NULL` as a comparable value.
+  ///
+  /// This is different from [neq] which treats `NULL` specially.
+  ///
+  /// ```dart
+  /// await supabase
+  ///     .from('users')
+  ///     .select()
+  ///     .isDistinct('age', null);
+  /// ```
+  // ignore: non_constant_identifier_names
+  PostgrestFilterBuilder<T> isDistinct(String column, Object? value) {
+    return copyWithUrl(appendSearchParams(column, 'isdistinct.$value'));
+  }
+
   @override
   PostgrestFilterBuilder<T> setHeader(String key, String value) {
     return PostgrestFilterBuilder(

packages/postgrest/test/filter_test.dart

@@ -477,6 +477,42 @@ void main() {
     expect(res[0]['username'], 'supabot');
   });
 
+  test('matchRegex - regex match (case sensitive)', () async {
+    final res = await postgrest
+        .from('users')
+        .select('username')
+        .matchRegex('username', '^supa.*');
+    expect(res, isNotEmpty);
+    for (final item in res) {
+      expect((item['username'] as String).startsWith('supa'), true);
+    }
+  });
+
+  test('imatchRegex - regex match (case insensitive)', () async {
+    final res = await postgrest
+        .from('users')
+        .select('username')
+        .imatchRegex('username', '^SUPA.*');
+    expect(res, isNotEmpty);
+    for (final item in res) {
+      expect(
+          (item['username'] as String).toLowerCase().startsWith('supa'), true);
+    }
+  });
+
+  test('isDistinct - treats NULL as comparable', () async {
+    final res = await postgrest
+        .from('users')
+        .select('username, data')
+        .isDistinct('data', null);
+    expect(res, isNotEmpty);
+    // isDistinct should return rows where data IS DISTINCT FROM null
+    // which means rows where data is NOT null
+    for (final item in res) {
+      expect(item['data'] != null, true);
+    }
+  });
+
   test('filter on rpc', () async {
     final List res = await postgrest.rpc('get_username_and_status',
         params: {'name_param': 'supabot'}).neq('status', 'ONLINE');