Syntax error while parsing ALTER TABLE with multiple commands

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Describe what's wrong

Parser throw syntax error while parsing ALTER TABLE query with MODIFY TTL and other commands.

Does it reproduce on recent release?

Yes, almost all releases have this problem.

How to reproduce

When we type such a sql, it causes syntax error.

> ALTER TABLE t MODIFY TTL d + toIntervalDay(1), ADD COLUMN c Date

Syntax error: failed at position 50 ('column'):

alter table t modify ttl d + interval 1 day, add column c Date;

Expected one of: token, Comma, Arrow, Dot, UUID, DoubleColon, MOD, DIV, NOT, BETWEEN, LIKE, ILIKE, NOT LIKE, NOT ILIKE, IN, NOT IN, GLOBAL IN, GLOBAL NOT IN, IS, AND, OR, QuestionMark, INTO OUTFILE, FORMAT, SETTINGS, end of query

But, if we put the MOFITY TTL element to the last, everything is ok.

> ALTER TABLE t ADD COLUMN c Date, MODIFY TTL d + toIntervalDay(1)

ALTER TABLE t
    ADD COLUMN `c` Date,
    MODIFY TTL d + toIntervalDay(1)

Query id: 7124ca11-3e98-4324-b3e7-399cc99ee010


0 rows in set. Elapsed: 0.004 sec.

Both AlterCommandList and TTLExpressionList are separate by COMMA , which may cause ambiguous behavior.

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Related code:

ClickHouse/src/Parsers/ParserAlterQuery.cpp

Lines 822 to 841 in b4f5d9c

	bool ParserAlterCommandList::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
	{
	auto command_list = std::make_shared<ASTExpressionList>();
	node = command_list;
	ParserToken s_comma(TokenType::Comma);
	ParserAlterCommand p_command(alter_object);
	do
	{
	ASTPtr command;
	if (!p_command.parse(pos, command, expected))
	return false;
	command_list->children.push_back(command);
	}
	while (s_comma.ignore(pos, expected));
	return true;
	}

ClickHouse/src/Parsers/ExpressionListParsers.cpp

Lines 830 to 834 in b4f5d9c

	bool ParserTTLExpressionList::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
	{
	return ParserList(std::make_unique<ParserTTLElement>(), std::make_unique<ParserToken>(TokenType::Comma), false)
	.parse(pos, node, expected);
	}