Method parseOrderByClause

pkg/sql/parser/select_clauses.go:526–583

parseOrderByClause parses "ORDER BY [ASC|DESC] [NULLS FIRST|LAST] [, ...]". Returns nil slice (no error) when ORDER BY is absent.

()

// parseOrderByClause parses "ORDER BY <expr> [ASC|DESC] [NULLS FIRST|LAST] [, ...]".
// Returns nil slice (no error) when ORDER BY is absent.
func (p *Parser) parseOrderByClause() ([]ast.OrderByExpression, error) {
	if !p.isType(models.TokenTypeOrder) {
		return nil, nil
	}
	p.advance() // Consume ORDER

	if !p.isType(models.TokenTypeBy) {
		return nil, p.expectedError("BY")
	}
	p.advance() // Consume BY

	var orderByExprs []ast.OrderByExpression
	for {
		expr, err := p.parseExpression()
		if err != nil {
			return nil, err
		}

		entry := ast.OrderByExpression{
			Expression: expr,
			Ascending:  true,
			NullsFirst: nil,
		}

		if p.isType(models.TokenTypeAsc) {
			entry.Ascending = true
			p.advance()
		} else if p.isType(models.TokenTypeDesc) {
			entry.Ascending = false
			p.advance()
		}

		nullsFirst, err := p.parseNullsClause()
		if err != nil {
			return nil, err
		}
		entry.NullsFirst = nullsFirst

		// ClickHouse WITH FILL per-entry tail:
		//   ORDER BY expr [ASC|DESC] WITH FILL [FROM x] [TO y] [STEP z]
		// Consume permissively; the clause is not modeled on the AST yet.
		if p.dialect == string(keywords.DialectClickHouse) &&
			p.isType(models.TokenTypeWith) &&
			strings.EqualFold(p.peekToken().Token.Value, "FILL") {
			p.advance() // WITH
			p.advance() // FILL
			p.skipClickHouseWithFillTail()
		}

		orderByExprs = append(orderByExprs, entry)

		if !p.isType(models.TokenTypeComma) {
			break
		}
		p.advance()
	}
	return orderByExprs, nil
}