Fix multiple parser issues from TODO.md

ast/ast.go

@@ -201,7 +201,8 @@ func (s *SettingExpr) End() token.Position { return s.Position }
 type InsertQuery struct {
 	Position token.Position `json:"-"`
 	Database string         `json:"database,omitempty"`
-	Table    string         `json:"table"`
+	Table    string         `json:"table,omitempty"`
+	Function *FunctionCall  `json:"function,omitempty"` // For INSERT INTO FUNCTION syntax
 	Columns  []*Identifier  `json:"columns,omitempty"`
 	Select   Statement      `json:"select,omitempty"`
 	Format   *Identifier    `json:"format,omitempty"`

lexer/lexer.go

@@ -118,6 +118,10 @@ func (l *Lexer) NextToken() Item {
 		return Item{Token: token.PERCENT, Value: "%", Pos: pos}
 	case '=':
 		l.readChar()
+		if l.ch == '=' {
+			l.readChar()
+			return Item{Token: token.EQ, Value: "==", Pos: pos}
+		}
 		return Item{Token: token.EQ, Value: "=", Pos: pos}
 	case '!':
 		if l.peekChar() == '=' {
@@ -407,7 +411,7 @@ func isIdentStart(ch rune) bool {
 }
 
 func isIdentChar(ch rune) bool {
-	return ch == '_' || unicode.IsLetter(ch) || unicode.IsDigit(ch)
+	return ch == '_' || ch == '$' || unicode.IsLetter(ch) || unicode.IsDigit(ch)
 }
 
 // Tokenize returns all tokens from the reader.

parser/expression.go

@@ -44,7 +44,7 @@ func (p *Parser) precedence(tok token.Token) int {
 		return CONCAT_PREC
 	case token.PLUS, token.MINUS:
 		return ADD_PREC
-	case token.ASTERISK, token.SLASH, token.PERCENT:
+	case token.ASTERISK, token.SLASH, token.PERCENT, token.DIV, token.MOD:
 		return MUL_PREC
 	case token.LPAREN, token.LBRACKET:
 		return CALL
@@ -173,7 +173,7 @@ func (p *Parser) parseInfixExpression(left ast.Expression) ast.Expression {
 	switch p.current.Token {
 	case token.PLUS, token.MINUS, token.ASTERISK, token.SLASH, token.PERCENT,
 		token.EQ, token.NEQ, token.LT, token.GT, token.LTE, token.GTE,
-		token.AND, token.OR, token.CONCAT:
+		token.AND, token.OR, token.CONCAT, token.DIV, token.MOD:
 		return p.parseBinaryExpression(left)
 	case token.NULL_SAFE_EQ:
 		return p.parseBinaryExpression(left)
@@ -1104,8 +1104,9 @@ func (p *Parser) parseDotAccess(left ast.Expression) ast.Expression {
 func (p *Parser) parseAlias(left ast.Expression) ast.Expression {
 	p.nextToken() // skip AS
 
+	// Alias can be an identifier or a keyword (ClickHouse allows keywords as aliases)
 	alias := ""
-	if p.currentIs(token.IDENT) {
+	if p.currentIs(token.IDENT) || p.current.Token.IsKeyword() {
 		alias = p.current.Value
 		p.nextToken()
 	}