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https://issues.apache.org/jira/browse/CALCITE-4079?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17151432#comment-17151432
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Julian Hyde commented on CALCITE-4079:
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bq. In general using a subclass during the initialization of the superclass is
a bad idea. I think we should prohibit this pattern.
Certainly discourage the practice. IntelliJ warns about it.
[~zabetak] and [~winipanda], In CALCITE-3923, I plan to move many rule
instances into 'holder' classes such as EnumerableRules and BindableRules. Note
that these holder classes are not super-classes of the rules, in fact do not
extend or inherit anything besides Object. Do you think that this pattern is
likely to increase class-loading problems?
We would remove a few of the old instance variables (usually called INSTANCE
and belonging to a rule class) in 1.24, but most would still exist, deprecated,
until 2.0. If people are getting deadlocks when using these instances then they
should stop.
> Dialect constants in SqlDialect can cause class initialization deadlock
> -----------------------------------------------------------------------
>
> Key: CALCITE-4079
> URL: https://issues.apache.org/jira/browse/CALCITE-4079
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.23.0
> Reporter: TANG Wen-hui
> Priority: Major
> Attachments: CALCITE-4079.01.patch,
> image-2020-07-01-19-27-25-354.png, image-2020-07-01-19-51-32-397.png
>
> Time Spent: 20m
> Remaining Estimate: 0h
>
> {code:java}
> /** @deprecated Use {@link AnsiSqlDialect#DEFAULT} instead. */
> @Deprecated // to be removed before 2.0
> public static final SqlDialect DUMMY =
> AnsiSqlDialect.DEFAULT;
> /** @deprecated Use {@link CalciteSqlDialect#DEFAULT} instead. */
> @Deprecated // to be removed before 2.0
> public static final SqlDialect CALCITE =
> CalciteSqlDialect.DEFAULT;{code}
> SqlDialect#DUMMY and SqlDialect#CALCITE are marked deprecated and have not be
> used in any places.
> It would be better to remove them to avoid class initialization deadlock.
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