[jira] [Commented] (CALCITE-7742) Test framework has non-determinstic tests

["Mihai Budiu (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-7742?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18108626#comment-18108626 ] 

Mihai Budiu commented on CALCITE-7742:
--------------------------------------

According to one of these clever agents, the bug is in the fact that all type factories share a single cache for interning types: DATATYPE_CACHE. Type equality is decided according to digests, but different factories may generate the same digest for different types. Consider these two types:

 
||createSqlType, precision||Type system||Stored precision||{{getPrecision()}}||Digest||Unparses to||
|{{{}CHAR{}}}, unspecified|DEFAULT|-1|1|{{CHAR}}|{{CHAR(1)}}|
|{{{}CHAR{}}}, unspecified|MySQL|-1|-1|{{CHAR}}|{{CHAR}}|

The type stores the type system inside, and that's why getPrecision() returns different results for the two.

When you call unparse, whether you get CHAR or CHAR(1)  depends on which test managed to install first its type in the cache – the cache considers them equal, since they have the same digest.

The clever agent produced a fix for this bug, but I am not sure it's a principled one. What is a principled fix?

> Test framework has non-determinstic tests
> -----------------------------------------
>
>                 Key: CALCITE-7742
>                 URL: https://issues.apache.org/jira/browse/CALCITE-7742
>             Project: Calcite
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 1.42.0
>            Reporter: Mihai Budiu
>            Priority: Minor
>
> Some tests intermittently fail in CI, here's an example output:
> {code:java}
> FAILURE   0.1sec, org.apache.calcite.rel.rel2sql.RelToSqlConverterRoundTripTest > testCastToChar()
>     java.lang.AssertionError:
>     Expected: is "SELECT CAST(`product_id` AS CHAR)\nFROM `foodmart`.`product`"
>          but: was "SELECT CAST(`product_id` AS CHAR(1))\nFROM `foodmart`.`product`" {code}
> Seemingly this is because there is some shared state between concurrent tests, e.g., perhaps a custom type system installed?



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