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https://issues.apache.org/jira/browse/IGNITE-10897?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16757312#comment-16757312
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Pavel Kuznetsov commented on IGNITE-10897:
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Discussed with [~vozerov].
If we got blocked select, first drop table will block till that select ends.
Unfortunately, first drop query mutates data structures before it acquires the
table lock, so second drop table would say, there is no such table.
Naive fix is to acquire lock earlier, but it doesn't solve the problem in all
cases. We could have some nodes that doesn't executing freezed select and some
nodes - does. So on the "freezed" nodes all drop table operations would be
blocked on the lock, the other nodes would execute drop.
Vladimir suggested fix concept: we need multi-phase mechanism for selects and
drops similar to PME.
1) Notify nodes that particular table should become disabled for all subsequent
selects
2) Wait for all running selects are done. This is selects that had been running
before we sent drop table.
3) Actually remove the tables.
> Blocked drop table operations cause strange issues
> --------------------------------------------------
>
> Key: IGNITE-10897
> URL: https://issues.apache.org/jira/browse/IGNITE-10897
> Project: Ignite
> Issue Type: Bug
> Components: sql
> Affects Versions: 2.6, 2.7
> Reporter: JiajunYang
> Assignee: Pavel Kuznetsov
> Priority: Major
>
> Reproduce steps to get a blocked drop table operation:
> 1.Create a table and put some data to a node with persistence enabled.
> 2.Do a select query targeting on the table which runs long time.
> 3.Drop the table before the select query end.
> Then u will see drop table operation blocks until the select query end.
> A strange issue cause by blocked drop table operations:
> 1.Do another drop table operation when there is a blocked drop table
> operation.This operation will also block.
> 2.Try to recreate the table with same name.Then you can see "table
> already exists" exception.
> 3.Try to drop the table again,then you can see
> "Table doesn't exist" exception.
>
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