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https://issues.apache.org/jira/browse/CASSANDRA-12102?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15364211#comment-15364211
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Alex Petrov commented on CASSANDRA-12102:
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> We actually do index decisions multiple times, on both coordinator (since we
> do have some validation that depends on the index) and replicas
I thought that after [CASSANDRA-10215], since index name is serialized as a
part of {{ReadCommand}}, it was already completely covered on the coordinator.
Might be that
[this|https://github.com/apache/cassandra/commit/e097efc5f6f76a0da8d15b307301dffff79e4a35#diff-861bc950c82973fb8f97f179e35be7f3R322]
condition is what you had in mind.
> we'd etablish some kind of "query plan" on the coordinator
That was exactly what [~blerer] said when we talked about: to introduce the
query planner.
In general, I agree on the fact it'd have to wait until the protocol version
bump and have an intersection with [CASSANDRA-10765].
> Refactor and simplify Filtering-related StatementRestriction part
> -----------------------------------------------------------------
>
> Key: CASSANDRA-12102
> URL: https://issues.apache.org/jira/browse/CASSANDRA-12102
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Alex Petrov
>
> {{RestrictionSet}} hierarchy was significantly improved by [CASSANDRA-11354],
> although filtering-related {{Restrictions}} are split with restrictions that
> would go through the 2i already in {{RowFilter}}.
> There's still a clear separation, although it's currently made in {{Index}}
> implementations and {{RowFilter}}, by removing things that were handled by
> {{Index}} for post-filtering like it's done
> [here|https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/db/ReadCommand.java#L374-L378].
>
> The primary concern is that we've seen several times that there are many
> corner-cases, so we may benefit from splitting columns that are handled by
> the index from ones that are handled by post-filtering early in code and
> possibly keeping them split for all parts of query.
> I suggest to split {{ClusteringColumnRestrictions#addRowFilterTo}} into two
> parts, {{addIndexRestrictions}} and {{addFilteringRestrictions}}. The change
> should be quite simple and make the code simpler to understand and extend the
> filtering / indexing rules.
> -One problem, as noted by [~blerer] is that index decision is made on
> replica, depending on cardinality, so splitting them too early might not
> work.- the decision is actually made on the coordinator after
> [CASSANDRA-10215], although that might involve a larger refactoring, although
> might still help to keep code related to indexing / filtering together.
> We can also validate that all restrictions have been respected (although we
> can do that now as well).
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