Method parseColumnCaseExpr

parser/parser_column.go:842–902

(pos Pos)

}

func (p *Parser) parseColumnCaseExpr(pos Pos) (*CaseExpr, error) {
	// CASE expr
	caseExpr := &CaseExpr{CasePos: pos}
	if err := p.expectKeyword(KeywordCase); err != nil {
		return nil, err
	}

	// case expr is optional
	if !p.matchKeyword(KeywordWhen) {
		expr, err := p.parseExpr(p.Pos())
		if err != nil {
			return nil, err
		}
		caseExpr.Expr = expr
	}

	// WHEN expr THEN expr
	whenClauses := make([]*WhenClause, 0)
	for p.matchKeyword(KeywordWhen) {
		whenPos := p.Pos()
		_ = p.lexer.consumeToken()
		whenCondition, err := p.parseExpr(p.Pos())
		if err != nil {
			return nil, err
		}

		thenPos := p.Pos()
		if err := p.expectKeyword(KeywordThen); err != nil {
			return nil, err
		}
		thenCondition, err := p.parseExpr(p.Pos())
		if err != nil {
			return nil, err
		}

		whenClauses = append(whenClauses, &WhenClause{
			WhenPos: whenPos,
			ThenPos: thenPos,
			When:    whenCondition,
			Then:    thenCondition,
		})
	}
	caseExpr.Whens = whenClauses

	// ELSE expr
	elsePos := p.Pos()
	if p.tryConsumeKeywords(KeywordElse) {
		elseExpr, err := p.parseExpr(p.Pos())
		if err != nil {
			return nil, err
		}
		caseExpr.ElsePos = elsePos
		caseExpr.Else = elseExpr
	}

	if err := p.expectKeyword(KeywordEnd); err != nil {
		return nil, err
	}