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https://issues.apache.org/jira/browse/IGNITE-6195?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16623503#comment-16623503
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Nikolay Izhikov commented on IGNITE-6195:
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[~SGrimstad] Do we have a chance to resolve this ticket until the code freeze
of 2.7?
> SQL: Do not allow JOINs on caches with different affinity functions
> -------------------------------------------------------------------
>
> Key: IGNITE-6195
> URL: https://issues.apache.org/jira/browse/IGNITE-6195
> Project: Ignite
> Issue Type: Bug
> Components: sql
> Affects Versions: 2.1
> Reporter: Vladimir Ozerov
> Assignee: Sergey Grimstad
> Priority: Major
> Labels: sql-stability, usability
> Fix For: 2.7
>
> Attachments: patch6195.patch
>
>
> Currently it is possible to execute JOIN on non-colocated caches. No
> exceptions will appear, user just receive incorrect result. We need to detect
> such situations and throw errors instead.
> *Proposed solution*
> Correct SQL result is possible when either distributed joins are enabled, or
> data is co-located properly. Under *proper* co-location we mean:
> 1) Participating {{PARTITIONED}} caches use the same affinity function
> 2) This affinity function doesn't depend on it's own previous state, i.e. it
> doesn't rely on {{AffinityFunctionContext.previousAssignment}}. For instance,
> {{RendezvousAffinityFunction}} doesn't use, while {{FairAffinityFunction}}
> does.
> As such, the following procedure should be implemented in order to determine
> whether SQL can be executed:
> 1) If {{distributedJoins}} are enabled - return, SQL can be executed
> 2) Get the list of participating caches
> 3) Exclude {{REPLICATED}} caches from that list
> 4) If all remaining caches belong to the same cache group - return, SQL can
> be executed
> 5) Get affinity function of the first cache
> 6) Check if affinity function doesn't use
> {{AffinityFunctionContext.previousAssignment}}. This could be controlled
> either through annotation, or through new method on {{AffinityFunction}}
> interface, e.g. {{boolean isDependOnPreviousState}}. If {{false}} - throw an
> exception
> 7) Check if affinity functions of all caches are equal through standard
> {{equals()}} method. If {{false}} - throw an exception.
> 8) Otherwise - SQL can be executed safely.
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