Method parseUnpivotClause

pkg/sql/parser/pivot.go:193–266

parseUnpivotClause parses UNPIVOT (value_col FOR name_col IN (columns)). The current token must be the UNPIVOT keyword.

()

// parseUnpivotClause parses UNPIVOT (value_col FOR name_col IN (columns)).
// The current token must be the UNPIVOT keyword.
func (p *Parser) parseUnpivotClause() (*ast.UnpivotClause, error) {
	pos := p.currentLocation()
	p.advance() // consume UNPIVOT

	if !p.isType(models.TokenTypeLParen) {
		return nil, p.expectedError("( after UNPIVOT")
	}
	p.advance() // consume (

	// Parse value column name
	if !p.isIdentifier() {
		return nil, p.expectedError("value column name in UNPIVOT")
	}
	valueCol := p.currentToken.Token.Value
	p.advance()

	// Expect FOR keyword
	if !p.isType(models.TokenTypeFor) {
		return nil, p.expectedError("FOR in UNPIVOT clause")
	}
	p.advance() // consume FOR

	// Parse name column
	if !p.isIdentifier() {
		return nil, p.expectedError("name column after FOR in UNPIVOT")
	}
	nameCol := p.currentToken.Token.Value
	p.advance()

	// Expect IN keyword
	if !p.isType(models.TokenTypeIn) {
		return nil, p.expectedError("IN in UNPIVOT clause")
	}
	p.advance() // consume IN

	// Expect opening parenthesis for column list
	if !p.isType(models.TokenTypeLParen) {
		return nil, p.expectedError("( after IN in UNPIVOT")
	}
	p.advance() // consume (

	// Parse IN columns
	var cols []string
	for !p.isType(models.TokenTypeRParen) && !p.isType(models.TokenTypeEOF) {
		if !p.isIdentifier() {
			return nil, p.expectedError("column name in UNPIVOT IN list")
		}
		cols = append(cols, renderQuotedIdent(p.currentToken.Token))
		p.advance()
		if p.isType(models.TokenTypeComma) {
			p.advance()
		}
	}

	if len(cols) == 0 {
		return nil, p.expectedError("at least one column in UNPIVOT IN list")
	}
	if !p.isType(models.TokenTypeRParen) {