Parse sql variables

sqlparser/lib/src/ast/ast.dart

@@ -12,6 +12,7 @@ part 'expressions/expressions.dart';
 part 'expressions/literals.dart';
 part 'expressions/reference.dart';
 part 'expressions/simple.dart';
+part 'expressions/variables.dart';
 
 part 'statements/select.dart';
 
@@ -40,4 +41,7 @@ abstract class AstVisitor<T> {
   T visitIsExpression(IsExpression e);
   T visitLiteral(Literal e);
   T visitReference(Reference e);
+
+  T visitNumberedVariable(NumberedVariable e);
+  T visitNamedVariable(ColonNamedVariable e);
 }

sqlparser/lib/src/ast/expressions/variables.dart

@@ -0,0 +1,43 @@
+part of '../ast.dart';
+
+mixin Variable on Expression {}
+
+/// A "?" or "?123" variable placeholder
+class NumberedVariable extends Expression with Variable {
+  final Token questionMark;
+  final int explicitIndex;
+
+  NumberedVariable(this.questionMark, this.explicitIndex);
+
+  @override
+  T accept<T>(AstVisitor<T> visitor) {
+    return visitor.visitNumberedVariable(this);
+  }
+
+  @override
+  Iterable<AstNode> get childNodes => const [];
+
+  @override
+  bool contentEquals(NumberedVariable other) {
+    return other.explicitIndex == explicitIndex;
+  }
+}
+
+class ColonNamedVariable extends Expression with Variable {
+  final String name;
+
+  ColonNamedVariable(this.name);
+
+  @override
+  T accept<T>(AstVisitor<T> visitor) {
+    return visitor.visitNamedVariable(this);
+  }
+
+  @override
+  Iterable<AstNode> get childNodes => [];
+
+  @override
+  bool contentEquals(ColonNamedVariable other) {
+    return other.name == name;
+  }
+}

sqlparser/lib/src/ast/statements/select.dart

@@ -1,6 +1,7 @@
 part of '../ast.dart';
 
 class SelectStatement extends AstNode {
+  final bool distinct;
   final Expression where;
   final List<ResultColumn> columns;
   final List<Queryable> from;
@@ -8,7 +9,12 @@ class SelectStatement extends AstNode {
   final Limit limit;
 
   SelectStatement(
-      {this.where, this.columns, this.from, this.orderBy, this.limit});
+      {this.distinct,
+      this.where,
+      this.columns,
+      this.from,
+      this.orderBy,
+      this.limit});
 
   @override
   T accept<T>(AstVisitor<T> visitor) {

sqlparser/lib/src/reader/parser/parser.dart

@@ -100,6 +100,13 @@ class Parser {
   SelectStatement select() {
     if (!_match(const [TokenType.select])) return null;
 
+    var distinct = false;
+    if (_matchOne(TokenType.distinct)) {
+      distinct = true;
+    } else if (_matchOne(TokenType.all)) {
+      distinct = false;
+    }
+
     final resultColumns = <ResultColumn>[];
     do {
       resultColumns.add(_resultColumn());
@@ -112,6 +119,7 @@ class Parser {
     final limit = _limit();
 
     return SelectStatement(
+      distinct: distinct,
       columns: resultColumns,
       from: from,
       where: where,
@@ -446,6 +454,11 @@ class Parser {
       return UnaryExpression(operator, expression);
     }
 
+    return _postfix();
+  }
+
+  Expression _postfix() {
+    // todo parse ISNULL, NOTNULL, NOT NULL, etc.
     return _primary();
   }
 
@@ -481,6 +494,21 @@ class Parser {
           return Reference(columnName: first.identifier);
         }
         break;
+      case TokenType.questionMark:
+        final mark = _previous;
+
+        if (_matchOne(TokenType.numberLiteral)) {
+          return NumberedVariable(mark, _parseNumber(_previous.lexeme).toInt());
+        } else {
+          return NumberedVariable(mark, null);
+        }
+        break;
+      case TokenType.colon:
+        final identifier = _consume(TokenType.identifier,
+            'Expected an identifier for the named variable') as IdentifierToken;
+        final content = identifier.identifier;
+
+        return ColonNamedVariable(':$content');
       default:
         break;
     }

sqlparser/lib/src/reader/tokenizer/scanner.dart

@@ -106,6 +106,13 @@ class Scanner {
         _addToken(TokenType.tilde);
         break;
 
+      case '?':
+        _addToken(TokenType.questionMark);
+        break;
+      case ':':
+        _addToken(TokenType.colon);
+        break;
+
       case 'x':
         if (_match("'")) {
           _string(binary: false);

sqlparser/lib/src/reader/tokenizer/token.dart

@@ -34,6 +34,12 @@ enum TokenType {
   or,
   tilde,
 
+  questionMark,
+  colon,
+  // todo at and dollarSign are currently not used
+  at,
+  dollarSign,
+
   stringLiteral,
   numberLiteral,
   $true,
@@ -45,6 +51,8 @@ enum TokenType {
   identifier,
 
   select,
+  distinct,
+  all,
   from,
   as,
   where,
@@ -71,6 +79,8 @@ enum TokenType {
 
 const Map<String, TokenType> keywords = {
   'SELECT': TokenType.select,
+  'DISTINCT': TokenType.distinct,
+  'ALL': TokenType.all,
   'FROM': TokenType.from,
   'NATURAL': TokenType.natural,
   'LEFT': TokenType.leftParen,

sqlparser/test/parser/expression_test.dart

@@ -31,4 +31,29 @@ void main() {
       ),
     );
   });
+
+  test('variables', () {
+    final scanner = Scanner('? * ?3 + ?2 == :test');
+    final tokens = scanner.scanTokens();
+    final parser = Parser(tokens);
+
+    final expression = parser.expression();
+
+    enforceEqual(
+      expression,
+      BinaryExpression(
+        BinaryExpression(
+          BinaryExpression(
+            NumberedVariable(token(TokenType.questionMark), null),
+            token(TokenType.star),
+            NumberedVariable(token(TokenType.questionMark), 3),
+          ),
+          token(TokenType.plus),
+          NumberedVariable(token(TokenType.questionMark), 2),
+        ),
+        token(TokenType.doubleEqual),
+        ColonNamedVariable(':test'),
+      ),
+    );
+  });
 }