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https://issues.apache.org/jira/browse/CASSANDRA-18796?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17759082#comment-17759082
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Brandon Williams commented on CASSANDRA-18796:
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bq.  issue a WARN if the number of sstables searched is over some threshold

Seems like we could have a warn and fail guardrail based on the number of 
sstables searched and both could have reasonable defaults to prevent the 
'untuned LCS' case from happening.

> Optionally fail when a non-partition-restricted query is issued against a 
> storage-attached index with a backing table using LCS
> -------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-18796
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-18796
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Feature/2i Index, Feature/SAI, Local/Compaction/LCS
>            Reporter: Caleb Rackliffe
>            Assignee: Caleb Rackliffe
>            Priority: Normal
>             Fix For: 5.0.x, 5.x
>
>
> With LCS, we will have potentially thousands of SSTables for a given user 
> table. Storage-attached also means SSTable-attached, and searching thousands 
> of attached indexes is not going to scale well at all locally, due to the 
> sheer number of searches and amount of postings list merging involved. We 
> should have a guardrail to prohibit this by default.
> Partition-restricted queries, the use-case SAI is broadly designed for, 
> should be very efficient.



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