drift/sqlparser

sqlparser

An sql parser and static analyzer, written in pure Dart. At the moment, this library only targets the sqlite dialect and some advanced features aren't supported yet.

Features

This library can parse most statements and perform type analysis for parameters and returned columns. It supports joins, group by, nested sql statements, updates and deletes, and more.

Just parsing

You can parse the abstract syntax tree of sqlite statements with SqlEngine.parse.

import 'package:sqlparser/sqlparser.dart';

final engine = SqlEngine();
final result = engine.parse('''
SELECT f.* FROM frameworks f
  INNER JOIN uses_language ul ON ul.framework = f.id
  INNER JOIN languages l ON l.id = ul.language
WHERE l.name = 'Dart'
ORDER BY f.name ASC, f.popularity DESC
LIMIT 5 OFFSET 5 * 3
  ''');
// result.rootNode contains the select statement in tree form

Analysis

Given information about all tables and a sql statement, this library can:

1. Determine which result columns a query is going to have, including types and nullability
2. Make an educated guess about what type the variables in the query should have (it's not really possible to be 100% accurate about this because sqlite is very flexible at types, but this library gets it mostly right)
3. Issue basic warnings about queries that are syntactically valid but won't run (references unknown tables / columns, uses undefined functions, etc.)

To use the analyzer, first register all known tables via SqlEngine.registerTable. Then, SqlEngine.analyze(sql) gives you an AnalysisContext which contains an annotated ast and information about errors. The type of result columns and expressions can be inferred by using AnalysisContext.typeOf(). Here's an example:

final id = TableColumn('id', const ResolvedType(type: BasicType.int));
final content = TableColumn('content', const ResolvedType(type: BasicType.text));
final demoTable = Table(
  name: 'demo',
  resolvedColumns: [id, content],
);
final engine = SqlEngine()..registerTable(demoTable);

final context =
    engine.analyze('SELECT id, d.content, *, 3 + 4 FROM demo AS d');

final select = context.root as SelectStatement;
final resolvedColumns = select.resolvedColumns;

resolvedColumns.map((c) => c.name)); // id, content, id, content, 3 + 4
resolvedColumns.map((c) => context.typeOf(c).type.type) // int, text, int, text, int, int

But why?

Moor, a persistence library for Dart apps, uses this package to generate type-safe methods from sql.

Limitations

Most on this list is just not supported yet because I didn't found a use case for them yet. If you need them, just leave an issue and I'll try to implement them soon.

• For now, INSERT statements are not supported, but they will be soon.
• Windowing is not supported yet
• Compound select statements (UNION / INTERSECT) are not supported yet
• Common table expressions are not supported
• Some advanced expressions, like CASTs aren't supported yet.

If you run into parsing errors with what you think is valid sql, please create an issue.

Thanks

• To Bob Nystrom for his amazing "Crafting Interpreters" book, which was incredibly helpful when writing the parser.
• To the authors of SQLDelight. This library uses their algorithm for type inference.