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https://issues.apache.org/jira/browse/CALCITE-7123?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18030152#comment-18030152
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Priyanka commented on CALCITE-7123:
-----------------------------------
Yeah, that's what didn't make sense to me either. But on investigating further,
I found this:
[Druid’s STRING null/empty
handling|https://imply.io/blog/numeric-column-null-checks-apache-druid/]
{noformat}
Traditionally, Druid considered the empty string, '', and null values as
equivalent for string columns.{noformat}
{noformat}
In newer versions, druid.generic.useDefaultValueForNull=false makes NULL
preserved properly.{noformat}
This could be the reason.
> Query doesn't work as expected when using COALESCE or CASE in the group by
> query
> --------------------------------------------------------------------------------
>
> Key: CALCITE-7123
> URL: https://issues.apache.org/jira/browse/CALCITE-7123
> Project: Calcite
> Issue Type: Bug
> Components: avatica
> Affects Versions: 1.39.0
> Reporter: Priyanka
> Priority: Major
> Attachments: image-2025-08-03-21-12-40-517.png,
> image-2025-08-03-21-13-52-179.png, image-2025-08-03-21-18-10-506.png,
> image-2025-08-14-11-56-16-650.png, image-2025-10-15-10-09-28-638.png,
> image-2025-10-15-10-09-55-877.png, image-2025-10-15-10-11-07-510.png,
> image-2025-10-15-10-11-22-457.png
>
>
> Running the following query directly on the Druid UI returns the expected
> results:
> {code:java}
> SELECT
> FLOOR("__time" TO DAY) AS "createtime.day",
> COALESCE("parentName", "stockName") AS "unitName",
> COUNT(*) AS "count"
> FROM
> "druid"."events"
> WHERE "customerName" = 'x' AND "__time" >=
> TIMESTAMP '2025-05-31 22:00:00.000' AND "__time" <= TIMESTAMP '2025-06-12
> 21:59:59.000'
> AND (FALSE = true OR "fleetName" IN ('y'))
> AND (FALSE = false OR "eventTemplateName" IN
> (null))
> AND (FALSE = false OR "consistNumber" IN (null))
> AND (FALSE = false OR ("parentName" IS NOT NULL
> AND "stockName" IN (null)))
> AND (FALSE = false OR (COALESCE("parentName",
> "stockName") IN (null)))
> AND (FALSE = false OR "locationName" IN (null))
> AND (FALSE = false OR "eventCategory" IN (null))
> AND (FALSE = false OR "eventPriorityName" IN
> (null))
> AND (FALSE = false OR null)
> AND (FALSE = false OR "active" = null)
> GROUP BY FLOOR("__time" TO DAY) ,
> COALESCE("parentName", "stockName") {code}
> But when it goes through Calcite, it returns the stockName always as the
> unitName, even if the parentName is available.
> Testing with CASE instead of COALESCE or using a CAST for the type also
> didn't have any effect with Calcite.
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