Fix support for multiple array join statements

[hermanschaaf]

Though not explicitly documented, in practice, ClickHouse supports multiple consecutive ARRAY JOIN statements, such as:

SELECT
    v,
    j
FROM t1
    ARRAY JOIN JSONExtractArrayRaw(a) AS j
    ARRAY JOIN array(
    JSONExtractString(j, 'x'),
    JSONExtractString(j, 'y')
) AS v;

Before this change, such queries failed parsing, as there was an assumption of only a single ARRAY JOIN statement in the parser logic. This change adds a test for this case and modifies the code to allow multiple ARRAY JOIN statements.

Example

Here is a minimal reproduction that can be tested on a ClickHouse server vs the ClickHouse SQL Parser:

CREATE TABLE t1
(
    a String
)
ENGINE = Memory;

INSERT INTO t1 VALUES
('[{"x":"1","y":"2"}]');

SELECT
    v,
    j
FROM t1
ARRAY JOIN JSONExtractArrayRaw(a) AS j
ARRAY JOIN array(
    JSONExtractString(j, 'x'),
    JSONExtractString(j, 'y')
) AS v;

[coveralls]

Pull Request Test Coverage Report for Build 21181160987

Details

• 14 of 22 (63.64%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.006%) to 51.201%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
parser/parser_query.go	8	10	80.0%
parser/walk.go	2	4	50.0%
parser/ast.go	4	8	50.0%

Totals
Change from base Build 21066744130:	0.006%
Covered Lines:	8017
Relevant Lines:	15658

---

💛 - Coveralls

[git-hulk]

@hermanschaaf Thanks for your great fix.