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InstantDB Flutter

Queries API

InstantDB uses InstaQL, a declarative query language that provides powerful filtering, sorting, and relationship traversal capabilities. All queries are reactive by default and automatically update when underlying data changes.

Query Methods

subscribeQuery()

Create a reactive query that automatically updates when data changes.

Signal<QueryResult> subscribeQuery(Map<String, dynamic> query)

Parameters:

  • query (Map<String, dynamic>): InstaQL query object

Returns: Signal<QueryResult> - Reactive signal containing query results

Example:

final todosSignal = db.subscribeQuery({
  'todos': {
    'where': {'completed': false},
    'orderBy': {'createdAt': 'desc'},
    'limit': 10,
  },
});


// Use in reactive widgets
Watch((context) {
  final result = todosSignal.value;
  final todos = result.data?['todos'] ?? [];
  return TodoList(todos: todos);
});

queryOnce()

Execute a one-time query without creating a subscription.

Future<QueryResult> queryOnce(Map<String, dynamic> query)

Parameters:

  • query (Map<String, dynamic>): InstaQL query object

Returns: Future<QueryResult> - Query result

Example:

final result = await db.queryOnce({
  'users': {
    'where': {'role': 'admin'},
    'limit': 5,
  },
});


final adminUsers = result.data?['users'] ?? [];
print('Found ${adminUsers.length} admin users');

QueryResult

Result object returned by query operations.

class QueryResult {
  final Map<String, dynamic>? data;
  final String? error;
  final bool isLoading;
}

Properties:

  • data (Map<String, dynamic>?): Query result data indexed by entity type
  • error (String?): Error message if query failed
  • isLoading (bool): Whether query is currently loading

InstaQL Syntax

Basic Query Structure

{
  'entityType': {
    'where': {...},      // Filtering conditions
    'orderBy': {...},    // Sorting specification
    'limit': 10,         // Maximum results
    'offset': 20,        // Skip results (pagination)
    'include': {...},    // Include related entities
  }
}

Simple Queries

// Get all entities
{'users': {}}


// Get with limit
{'posts': {'limit': 10}}


// Get specific entity by ID
{'users': {'where': {'id': 'user-123'}}}


// Multiple entity types
{
  'users': {'limit': 5},
  'posts': {'where': {'published': true}},
}

Where Conditions

Equality

// Exact match
{'users': {'where': {'name': 'John Doe'}}}


// Multiple conditions (AND)
{
  'posts': {
    'where': {
      'published': true,
      'authorId': 'user-123',
    }
  }
}

Comparison Operators

{
  'posts': {
    'where': {
      'createdAt': {
        '\$gte': DateTime.now().subtract(Duration(days: 7)).millisecondsSinceEpoch,
        '\$lt': DateTime.now().millisecondsSinceEpoch,
      },
      'viewCount': {'\$gt': 100},
      'rating': {'\$lte': 5},
    }
  }
}

Available operators:

  • $gt: Greater than
  • $gte: Greater than or equal
  • $lt: Less than
  • $lte: Less than or equal
  • $ne: Not equal
  • $eq: Equal (explicit equality)

String Operators

{
  'users': {
    'where': {
      'email': {'\$like': '%@gmail.com'},           // Contains pattern
      'name': {'\$ilike': '%john%'},                // Case-insensitive like
      'username': {'\$startsWith': 'admin_'},       // Starts with
      'bio': {'\$endsWith': '...'},                 // Ends with
      'status': {'\$regex': '^(active|pending)\$'}, // Regular expression
    }
  }
}

Array Operators

{
  'posts': {
    'where': {
      'tags': {'\$contains': 'flutter'},            // Array contains value
      'categories': {'\$containsAny': ['tech', 'programming']}, // Contains any
      'skills': {'\$size': {'\$gte': 3}},          // Array size condition
      'permissions': {'\$in': ['read', 'write']},  // Value in array
      'blockedUsers': {'\$nin': ['user-123']},     // Value not in array
    }
  }
}

Existence Operators

{
  'users': {
    'where': {
      'profilePicture': {'\$exists': true},         // Field exists
      'deletedAt': {'\$isNull': true},              // Field is null
      'verifiedAt': {'\$isNotNull': true},          // Field is not null
    }
  }
}

Logical Operators

AND Operator

// Implicit AND (default)
{
  'users': {
    'where': {
      'active': true,
      'role': 'user', // Both conditions must be true
    }
  }
}


// Explicit AND
{
  'users': {
    'where': {
      '\$and': [
        {'age': {'\$gte': 18}},
        {'status': 'verified'},
      ]
    }
  }
}

OR Operator

{
  'users': {
    'where': {
      '\$or': [
        {'role': 'admin'},
        {'role': 'moderator'},
        {'permissions': {'\$contains': 'admin'}},
      ]
    }
  }
}

NOT Operator

{
  'posts': {
    'where': {
      '\$not': {
        'status': 'deleted',
      }
    }
  }
}

Complex Logic

{
  'users': {
    'where': {
      '\$and': [
        {'active': true},
        {
          '\$or': [
            {'role': 'admin'},
            {
              '\$and': [
                {'role': 'user'},
                {'permissions': {'\$contains': 'write'}},
              ]
            }
          ]
        }
      ]
    }
  }
}

Sorting (orderBy)

Single Field

// Ascending order
{'posts': {'orderBy': {'createdAt': 'asc'}}}


// Descending order
{'posts': {'orderBy': {'createdAt': 'desc'}}}

Multiple Fields

{
  'posts': {
    'orderBy': [
      {'priority': 'desc'},      // Primary sort
      {'createdAt': 'asc'},      // Secondary sort
      {'title': 'asc'},          // Tertiary sort
    ]
  }
}

Dynamic Sorting

// Sort by different fields based on conditions
String sortField = userPreference == 'date' ? 'createdAt' : 'title';
String sortDirection = ascending ? 'asc' : 'desc';


final query = {
  'posts': {
    'orderBy': {sortField: sortDirection},
  }
};

Pagination

Limit and Offset

{
  'posts': {
    'orderBy': {'createdAt': 'desc'},
    'limit': 20,        // Maximum 20 results
    'offset': 40,       // Skip first 40 results (page 3)
  }
}

Cursor-Based Pagination

// First page
{
  'posts': {
    'orderBy': {'createdAt': 'desc'},
    'limit': 20,
  }
}


// Next page using cursor
{
  'posts': {
    'orderBy': {'createdAt': 'desc'},
    'limit': 20,
    'before': lastPostCreatedAt,    // Get posts before this timestamp
  }
}


// Previous page
{
  'posts': {
    'orderBy': {'createdAt': 'desc'},
    'limit': 20,
    'after': firstPostCreatedAt,    // Get posts after this timestamp
  }
}

Pagination Helper

class PaginationHelper {
  static Map<String, dynamic> buildQuery({
    required String entityType,
    required int page,
    required int pageSize,
    Map<String, dynamic>? where,
    Map<String, String>? orderBy,
  }) {
    return {
      entityType: {
        if (where != null) 'where': where,
        if (orderBy != null) 'orderBy': orderBy,
        'limit': pageSize,
        'offset': page * pageSize,
      }
    };
  }
}


// Usage
final query = PaginationHelper.buildQuery(
  entityType: 'posts',
  page: 2,           // Third page (0-indexed)
  pageSize: 10,
  where: {'published': true},
  orderBy: {'createdAt': 'desc'},
);

Relationships and Includes

Basic Includes

{
  'posts': {
    'include': {
      'author': {},              // Include author for each post
      'comments': {              // Include comments for each post
        'limit': 5,
        'orderBy': {'createdAt': 'desc'},
      },
    }
  }
}

Nested Includes

{
  'posts': {
    'include': {
      'author': {
        'include': {
          'profile': {},         // Include author's profile
        }
      },
      'comments': {
        'include': {
          'author': {},          // Include comment authors
        },
        'orderBy': {'createdAt': 'asc'},
      },
    }
  }
}

Conditional Includes

{
  'posts': {
    'include': {
      'author': {
        'where': {'active': true},  // Only include if author is active
      },
      'comments': {
        'where': {'approved': true}, // Only approved comments
        'limit': 10,
      },
    }
  }
}

Complex Relationship Queries

// Posts with their authors and latest comments
{
  'posts': {
    'where': {'published': true},
    'include': {
      'author': {
        'include': {
          'profile': {},
        }
      },
      'comments': {
        'where': {'approved': true},
        'orderBy': {'createdAt': 'desc'},
        'limit': 3,
        'include': {
          'author': {
            'include': {
              'profile': {},
            }
          }
        }
      },
      'tags': {},
      'category': {},
    },
    'orderBy': {'publishedAt': 'desc'},
    'limit': 10,
  }
}

Lookups

Use lookups to reference entities by attributes other than ID.

lookup() Function

LookupRef lookup(String entityType, String attribute, dynamic value)

Parameters:

  • entityType (String): Type of entity to lookup
  • attribute (String): Attribute to match against
  • value (dynamic): Value to match

Returns: LookupRef - Lookup reference object

Lookup Examples

// Reference user by email instead of ID
{
  'posts': {
    'where': {
      'author': lookup('users', 'email', 'john@example.com'),
    }
  }
}


// Create post with author lookup
await db.transact([
  ...db.create('posts', {
    'id': db.id(),
    'title': 'My Post',
    'authorId': lookup('users', 'email', 'author@example.com'),
  }),
]);


// Multiple lookups
{
  'posts': {
    'where': {
      'author': lookup('users', 'username', 'john_doe'),
      'category': lookup('categories', 'slug', 'technology'),
    }
  }
}

Advanced Query Patterns

Search Functionality

class SearchQueries {
  static Map<String, dynamic> searchPosts(String searchTerm) {
    return {
      'posts': {
        'where': {
          '\$or': [
            {'title': {'\$ilike': '%$searchTerm%'}},
            {'content': {'\$ilike': '%$searchTerm%'}},
            {'tags': {'\$contains': searchTerm.toLowerCase()}},
          ]
        },
        'orderBy': {'relevanceScore': 'desc'},
        'limit': 20,
      }
    };
  }


  static Map<String, dynamic> searchUsers(String query) {
    return {
      'users': {
        'where': {
          '\$or': [
            {'name': {'\$ilike': '%$query%'}},
            {'username': {'\$ilike': '%$query%'}},
            {'email': {'\$like': '%$query%'}},
          ],
          'active': true, // Only active users
        },
        'orderBy': [
          {'verified': 'desc'},  // Verified users first
          {'name': 'asc'},       // Then by name
        ],
        'limit': 10,
      }
    };
  }
}

Aggregation Queries

// Get user statistics
{
  'users': {
    'where': {'active': true},
    'include': {
      'posts': {
        'where': {'published': true},
        // Count will be included in results
      },
      'comments': {
        'where': {'approved': true},
      },
    }
  }
}


// Posts with comment counts
{
  'posts': {
    'where': {'published': true},
    'include': {
      'comments': {
        'where': {'approved': true},
      },
      'likes': {},  // Will include like count
    },
    'orderBy': {'commentCount': 'desc'},
  }
}

Time-Based Queries

class TimeQueries {
  static Map<String, dynamic> getRecentPosts(Duration duration) {
    final since = DateTime.now().subtract(duration).millisecondsSinceEpoch;


    return {
      'posts': {
        'where': {
          'createdAt': {'\$gte': since},
          'published': true,
        },
        'orderBy': {'createdAt': 'desc'},
      }
    };
  }


  static Map<String, dynamic> getPostsInRange(DateTime start, DateTime end) {
    return {
      'posts': {
        'where': {
          'createdAt': {
            '\$gte': start.millisecondsSinceEpoch,
            '\$lt': end.millisecondsSinceEpoch,
          }
        },
        'orderBy': {'createdAt': 'asc'},
      }
    };
  }


  static Map<String, dynamic> getTrendingPosts() {
    final lastWeek = DateTime.now().subtract(Duration(days: 7)).millisecondsSinceEpoch;


    return {
      'posts': {
        'where': {
          'createdAt': {'\$gte': lastWeek},
          'viewCount': {'\$gt': 100},
        },
        'orderBy': [
          {'viewCount': 'desc'},
          {'likeCount': 'desc'},
          {'commentCount': 'desc'},
        ],
        'limit': 20,
      }
    };
  }
}

Conditional Queries

class ConditionalQueries {
  static Map<String, dynamic> buildUserQuery({
    String? role,
    bool? active,
    DateTime? createdAfter,
    List<String>? excludeIds,
  }) {
    final where = <String, dynamic>{};


    if (role != null) {
      where['role'] = role;
    }


    if (active != null) {
      where['active'] = active;
    }


    if (createdAfter != null) {
      where['createdAt'] = {'\$gte': createdAfter.millisecondsSinceEpoch};
    }


    if (excludeIds != null && excludeIds.isNotEmpty) {
      where['id'] = {'\$nin': excludeIds};
    }


    return {
      'users': {
        if (where.isNotEmpty) 'where': where,
        'orderBy': {'createdAt': 'desc'},
      }
    };
  }
}


// Usage
final query = ConditionalQueries.buildUserQuery(
  role: 'user',
  active: true,
  createdAfter: DateTime.now().subtract(Duration(days: 30)),
  excludeIds: ['blocked-user-1', 'blocked-user-2'],
);

Query Optimization

Efficient Filtering

// ✅ Good: Filter at database level
{
  'posts': {
    'where': {
      'published': true,
      'authorId': currentUserId,
    },
    'limit': 10,
  }
}


// ❌ Avoid: Filter in application
{
  'posts': {} // Gets all posts, then filter in Dart code
}

Index-Friendly Queries

// ✅ Good: Use indexed fields for where conditions
{
  'posts': {
    'where': {
      'createdAt': {'\$gte': timestamp},  // Usually indexed
      'published': true,                  // Simple equality
    }
  }
}


// ❌ Less efficient: Complex string operations
{
  'posts': {
    'where': {
      'content': {'\$regex': 'complex.*pattern'},  // Expensive
    }
  }
}

Limit Result Sets

// Always use appropriate limits
{
  'posts': {
    'where': {'published': true},
    'limit': 20,  // Prevent loading too much data
    'orderBy': {'createdAt': 'desc'},
  }
}

Error Handling

Handle query errors appropriately:

Future<List<Map<String, dynamic>>> safeQuery(Map<String, dynamic> query) async {
  try {
    final result = await db.queryOnce(query);


    if (result.error != null) {
      print('Query error: ${result.error}');
      return [];
    }


    // Extract first entity type from results
    final entityType = query.keys.first;
    return (result.data?[entityType] as List? ?? [])
        .cast<Map<String, dynamic>>();


  } on InstantException catch (e) {
    print('InstantDB error: ${e.message}');
    return [];
  } catch (e) {
    print('Unexpected error: $e');
    return [];
  }
}

Query Builder Helper

Create a query builder for complex queries:

class QueryBuilder {
  final Map<String, dynamic> _query = {};


  QueryBuilder entity(String entityType) {
    _query[entityType] = <String, dynamic>{};
    return this;
  }


  QueryBuilder where(Map<String, dynamic> conditions) {
    final entityType = _query.keys.last;
    _query[entityType]['where'] = conditions;
    return this;
  }


  QueryBuilder orderBy(Map<String, String> ordering) {
    final entityType = _query.keys.last;
    _query[entityType]['orderBy'] = ordering;
    return this;
  }


  QueryBuilder limit(int count) {
    final entityType = _query.keys.last;
    _query[entityType]['limit'] = count;
    return this;
  }


  QueryBuilder offset(int count) {
    final entityType = _query.keys.last;
    _query[entityType]['offset'] = count;
    return this;
  }


  QueryBuilder include(Map<String, dynamic> includes) {
    final entityType = _query.keys.last;
    _query[entityType]['include'] = includes;
    return this;
  }


  Map<String, dynamic> build() => Map<String, dynamic>.from(_query);
}


// Usage
final query = QueryBuilder()
    .entity('posts')
    .where({
      'published': true,
      'createdAt': {'\$gte': DateTime.now().subtract(Duration(days: 7)).millisecondsSinceEpoch},
    })
    .orderBy({'createdAt': 'desc'})
    .limit(10)
    .include({
      'author': {},
      'comments': {'limit': 5},
    })
    .build();


final result = await db.queryOnce(query);

Next Steps

Explore related APIs: