Method parseSelectCommand

parser/parser.go:242–332

parseSelectCommand - Return ast.SelectCommand created from tokens and validate the syntax Example of input parsable to the ast.SelectCommand: SELECT col1, col2, col3 FROM tbl;

()

// Example of input parsable to the ast.SelectCommand:
// SELECT col1, col2, col3 FROM tbl;
func (parser *Parser) parseSelectCommand() (ast.Command, error) {
	// token.SELECT already at current position in parser
	selectCommand := &ast.SelectCommand{Token: parser.currentToken}

	// Ignore token.SELECT
	parser.nextToken()

	// optional DISTINCT
	if parser.currentToken.Type == token.DISTINCT {
		selectCommand.HasDistinct = true

		// Ignore token.DISTINCT
		parser.nextToken()
	}

	err := validateToken(parser.currentToken.Type, []token.Type{token.ASTERISK, token.IDENT, token.MAX, token.MIN, token.SUM, token.AVG, token.COUNT})
	if err != nil {
		return nil, err
	}

	if parser.currentToken.Type == token.ASTERISK {
		selectCommand.Space = append(selectCommand.Space, ast.Space{ColumnName: parser.currentToken})
		parser.nextToken()
	} else {
		for parser.currentToken.Type == token.IDENT || isAggregateFunction(parser.currentToken.Type) {
			if parser.currentToken.Type != token.IDENT {
				aggregateFunction := parser.currentToken
				parser.nextToken()
				err := validateTokenAndSkip(parser, []token.Type{token.LPAREN})
				if err != nil {
					return nil, err
				}
				if aggregateFunction.Type == token.COUNT {
					err = validateToken(parser.currentToken.Type, []token.Type{token.IDENT, token.ASTERISK})
				} else {
					err = validateToken(parser.currentToken.Type, []token.Type{token.IDENT})
				}
				if err != nil {
					return nil, err
				}
				selectCommand.Space = append(selectCommand.Space, ast.Space{ColumnName: parser.currentToken, AggregateFunc: &aggregateFunction})
				parser.nextToken()

				err = validateTokenAndSkip(parser, []token.Type{token.RPAREN})
				if err != nil {
					return nil, err
				}
			} else {
				// Get column name
				err = validateToken(parser.currentToken.Type, []token.Type{token.IDENT})
				if err != nil {
					return nil, err
				}
				selectCommand.Space = append(selectCommand.Space, ast.Space{ColumnName: parser.currentToken})
				parser.nextToken()
			}

			if parser.currentToken.Type != token.COMMA {