Failed to parse 'CASE WHEN' condition expression without brackets

[chenyele]

I had the following SQL statment:

SELECT
    CASE
        WHEN "metrics_all"."METRIC_ID" IS NULL OR "metrics_all"."SUB_METRIC" IS NULL THEN NULL
        WHEN "metrics_all"."METRIC_ID" > "metrics_all"."SUB_METRIC" THEN "metrics_all"."METRIC_ID"
        ELSE "metrics_all"."SUB_METRIC"
    END AS "MET"
FROM
    "mrs"."metrics_all" AS "metrics_all"
GROUP BY
    CASE
        WHEN "metrics_all"."METRIC_ID" IS NULL
        OR "metrics_all"."SUB_METRIC" IS NULL THEN NULL
        WHEN "metrics_all"."METRIC_ID" > "metrics_all"."SUB_METRIC" THEN "metrics_all"."METRIC_ID"
        ELSE "metrics_all"."SUB_METRIC"
    END

This SQL statment could be excuted by Command-line Client and clickhouse-jdbc-0.2.4：

But could not be exceuted by clickhouse-jdbc-0.3.1,because the SQL parse is mandatory ,and got the following error:
2021-09-15 19:58:44,058 | WARN | main | Parse error at line 3, column 48. Encountered: OR. If you believe the SQL is valid, please feel free to open an issue on Github with this warning and the following SQL attached.
SELECT
CASE
WHEN "metrics_all"."METRIC_ID" IS NULL OR "metrics_all"."SUB_METRIC" IS NULL THEN NULL
WHEN "metrics_all"."METRIC_ID" > "metrics_all"."SUB_METRIC" THEN "metrics_all"."METRIC_ID"
ELSE "metrics_all"."SUB_METRIC"
END AS "TEMP(Test)(2280873464)(0)"
FROM
"mrs"."metrics_all" AS "metrics_all"
GROUP BY
CASE
WHEN "metrics_all"."METRIC_ID" IS NULL
OR "metrics_all"."SUB_METRIC" IS NULL THEN NULL
WHEN "metrics_all"."METRIC_ID" > "metrics_all"."SUB_METRIC" THEN "metrics_all"."METRIC_ID"
ELSE "metrics_all"."SUB_METRIC"
END | ru.yandex.clickhouse.jdbc.parser.ClickHouseSqlParser.parse(ClickHouseSqlParser.java:71)

It seemed that the parser can not resolve 'OR' between 'When' and 'Then', so I had to add brackets like this to make it work:

SELECT
    CASE
        WHEN ("metrics_all"."METRIC_ID" IS NULL OR "metrics_all"."SUB_METRIC") IS NULL THEN NULL
        WHEN "metrics_all"."METRIC_ID" > "metrics_all"."SUB_METRIC" THEN "metrics_all"."METRIC_ID"
        ELSE "metrics_all"."SUB_METRIC"
    END AS "MET"
FROM
    "mrs"."metrics_all" AS "metrics_all"
GROUP BY
    CASE
        WHEN "metrics_all"."METRIC_ID" IS NULL
        OR "metrics_all"."SUB_METRIC" IS NULL THEN NULL
        WHEN "metrics_all"."METRIC_ID" > "metrics_all"."SUB_METRIC" THEN "metrics_all"."METRIC_ID"
        ELSE "metrics_all"."SUB_METRIC"
    END

[zhicwu]

Thnaks for reporting the issue. Yes, brackets are the workaround. Will need to clean up the mess of dealing with nested expressions.

https://github.com/ClickHouse/clickhouse-jdbc/blob/5e6f74b89354e60af7d0c9437eef0520ee9ffda1/clickhouse-jdbc/src/main/javacc/ClickHouseSqlParser.jj#L612-L615

[github-actions]

This issue has been automatically marked as stale because it has not had activity in the last year. It will be closed in 30 days if no further activity occurs. Please feel free to leave a comment if you believe the issue is still relevant. Thank you for your contributions!

[chernser]

new jdbc-v2 has no parser and no such issue.
workaround exists.