Method parseGroupByClause

pkg/sql/parser/select_clauses.go:451–512

parseGroupByClause parses "GROUP BY [, ...]" including ROLLUP, CUBE, GROUPING SETS, and MySQL's trailing WITH ROLLUP / WITH CUBE syntax. Returns nil slice (no error) when GROUP BY is absent.

()

// GROUPING SETS, and MySQL's trailing WITH ROLLUP / WITH CUBE syntax.
// Returns nil slice (no error) when GROUP BY is absent.
func (p *Parser) parseGroupByClause() ([]ast.Expression, error) {
	if !p.isType(models.TokenTypeGroup) {
		return nil, nil
	}
	p.advance() // Consume GROUP

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

	groupByExprs := make([]ast.Expression, 0, 4)
	for {
		var (
			expr ast.Expression
			err  error
		)

		switch {
		case p.isType(models.TokenTypeRollup):
			expr, err = p.parseRollup()
		case p.isType(models.TokenTypeCube):
			expr, err = p.parseCube()
		case p.currentToken.Token.Value == "GROUPING SETS" ||
			(p.isType(models.TokenTypeGrouping) && strings.EqualFold(p.peekToken().Token.Value, "SETS")):
			expr, err = p.parseGroupingSets()
		default:
			expr, err = p.parseExpression()
		}

		if err != nil {
			return nil, err
		}
		groupByExprs = append(groupByExprs, expr)

		if !p.isType(models.TokenTypeComma) {
			break
		}
		p.advance()
	}

	// MySQL / ClickHouse: GROUP BY col1 WITH ROLLUP / WITH CUBE / WITH TOTALS
	if p.isType(models.TokenTypeWith) {
		switch strings.ToUpper(p.peekToken().Token.Value) {
		case "ROLLUP":
			p.advance() // Consume WITH
			p.advance() // Consume ROLLUP
			groupByExprs = []ast.Expression{&ast.RollupExpression{Expressions: groupByExprs}}
		case "CUBE":
			p.advance() // Consume WITH
			p.advance() // Consume CUBE
			groupByExprs = []ast.Expression{&ast.CubeExpression{Expressions: groupByExprs}}
		case "TOTALS":
			// ClickHouse WITH TOTALS: adds a summary row with aggregate totals.
			// Consumed but not modeled on the AST (follow-up).
			p.advance() // Consume WITH
			p.advance() // Consume TOTALS
		}