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https://issues.apache.org/jira/browse/DRILL-5771?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16249355#comment-16249355
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ASF GitHub Bot commented on DRILL-5771:
---------------------------------------
Github user arina-ielchiieva commented on the issue:
https://github.com/apache/drill/pull/1014
@ilooner Paul has correctly described race condition issue. At planning
time when we have defined plugin configuration we want to make sure it would
stay the same during query execution. Relying on plugin configuration name is
unsafe since config under this particular name can change and it can be that
one fragment of the query is executed with one configuration and another with
different (typical race condition issue).
Regarding your last question, during physical plan creation I don't think
we deserialize DrillTable, we rather deserialize query fragments (it can be
seen from json profile). Also you can start looking, for example, from here:
https://github.com/apache/drill/blob/master/exec/java-exec/src/main/java/org/apache/drill/exec/work/QueryWorkUnit.java#L59
> Fix serDe errors for format plugins
> -----------------------------------
>
> Key: DRILL-5771
> URL: https://issues.apache.org/jira/browse/DRILL-5771
> Project: Apache Drill
> Issue Type: Bug
> Affects Versions: 1.11.0
> Reporter: Arina Ielchiieva
> Assignee: Arina Ielchiieva
> Priority: Minor
> Fix For: 1.12.0
>
>
> Create unit tests to check that all storage format plugins can be
> successfully serialized / deserialized.
> Usually this happens when query has several major fragments.
> One way to check serde is to generate physical plan (generated as json) and
> then submit it back to Drill.
> One example of found errors is described in the first comment. Another
> example is described in DRILL-5166.
> *Serde issues:*
> 1. Could not obtain format plugin during deserialization
> Format plugin is created based on format plugin configuration or its name.
> On Drill start up we load information about available plugins (its reloaded
> each time storage plugin is updated, can be done only by admin).
> When query is parsed, we try to get plugin from the available ones, it we can
> not find one we try to [create
> one|https://github.com/apache/drill/blob/3e8b01d5b0d3013e3811913f0fd6028b22c1ac3f/exec/java-exec/src/main/java/org/apache/drill/exec/store/dfs/FileSystemPlugin.java#L136-L144]
> but on other query execution stages we always assume that [plugin exists
> based on
> configuration|https://github.com/apache/drill/blob/3e8b01d5b0d3013e3811913f0fd6028b22c1ac3f/exec/java-exec/src/main/java/org/apache/drill/exec/store/dfs/FileSystemPlugin.java#L156-L162].
> For example, during query parsing we had to create format plugin on one node
> based on format configuration.
> Then we have sent major fragment to the different node where we used this
> format configuration we could not get format plugin based on it and
> deserialization has failed.
> To fix this problem we need to create format plugin during query
> deserialization if it's absent.
>
> 2. Absent hash code and equals.
> Format plugins are stored in hash map where key is format plugin config.
> Since some format plugin configs did not have overridden hash code and
> equals, we could not find format plugin based on its configuration.
> 3. Named format plugin usage
> Named format plugins configs allow to get format plugin by its name for
> configuration shared among all drillbits.
> They are used as alias for pre-configured format plugiins. User with admin
> priliges can modify them at runtime.
> Named format plugins configs are used instead of sending all non-default
> parameters of format plugin config, in this case only name is sent.
> Their usage in distributed system may cause raise conditions.
> For example,
> 1. Query is submitted.
> 2. Parquet format plugin is created with the following configuration
> (autoCorrectCorruptDates=>true).
> 3. Seralized named format plugin config with name as parquet.
> 4. Major fragment is sent to the different node.
> 5. Admin has changed parquet configuration for the alias 'parquet' on all
> nodes to autoCorrectCorruptDates=>false.
> 6. Named format is deserialized on the different node into parquet format
> plugin with configuration (autoCorrectCorruptDates=>false).
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