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https://issues.apache.org/jira/browse/CASSANDRA-18782?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Andres de la Peña updated CASSANDRA-18782:
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Fix Version/s: 5.0
5.1
(was: 5.x)
(was: 5.0.x)
Since Version: 5.0-alpha1
Source Control Link:
https://github.com/apache/cassandra/commit/b265b4658e007b6943d543a11c609b7ba5fd979f
Resolution: Fixed
Status: Resolved (was: Ready to Commit)
> Forbid analyzed SAI indexes on primary key columns
> --------------------------------------------------
>
> Key: CASSANDRA-18782
> URL: https://issues.apache.org/jira/browse/CASSANDRA-18782
> Project: Cassandra
> Issue Type: Bug
> Components: Feature/SAI
> Reporter: Andres de la Peña
> Assignee: Andres de la Peña
> Priority: Normal
> Fix For: 5.0, 5.1
>
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> Queries using SAI indexes don't find any results when the index is on a
> primary key column, the indexing uses analysis, and the queried value is
> different to the exact value of the column. For example:
> {code:java}
> CREATE TABLE t(k int, c text, PRIMARY KEY (k, c));
> CREATE INDEX ON t(c) USING 'sai' WITH OPTIONS = { 'case_sensitive' : false };
> INSERT INTO t(k, c) VALUES (1, 'A');
> SELECT * FROM t WHERE c = 'a'; -- no results found!!!
> {code}
> This happens because the {{ClusteringIndexFilter}} for the query doesn't take
> analysis into account. Thus, when that filter is applied by
> [{{QueryController#doesNotSelect(PrimaryKey)}}|https://github.com/apache/cassandra/blob/655a2455ac29395b0a303e6ad7fc4d458b18932d/src/java/org/apache/cassandra/index/sai/plan/QueryController.java#L194-L210]
> it rejects the results that have been correctly found by the index.
> An initial approach to solve this problem could be making
> {{ClusteringIndexFilter}} aware of the index analysis options. However, this
> would be problematic for paging. The first page of the query contains a
> restriction in the clustering that requires analysis. But subsequent queries
> will contain the last seen clustering, and we don’t want analysis in that
> case.
> Another approach would be not adding a {{ClusteringIndexFilter}} to the query
> restrictions when it contains this type of restriction on columns. However,
> this approach would create a weird situation where adding an index might make
> {{ALLOW FILTERING}} necessary in queries that wouldn’t need it without the
> index. This is the opposite of the natural way of things, where more indexes
> mean less AF needed. For example:
> {code:java}
> CREATE TABLE t(k int, c1 text, c2 int, PRIMARY KEY (k, c1, c2));
> CREATE INDEX idx ON t(c1) USING 'sai' WITH OPTIONS = { 'case_sensitive' :
> false };
> SELECT * FROM t WHERE k = 0 AND c1 = 'a' AND c2 = 0 ALLOW FILTERING;
> {code}
> The query would need AF because it has been translated into an index query
> without a clustering filter, and {{c2}} is not indexed.
> I think there is an ambiguity in the query, and it's not clear if it should
> use the secondary index filter and use analysis, or it should be a primary
> index query and not use analysis. Although we can default to one or another
> interpretation, both can serve different use cases. We will probably need
> some new CQL syntax to allow users to specify whether they want to use the
> secondary index or not.
> We can work on those CQL improvements during the second phase of SAI. In the
> meantime, I think we should simply forbid the creation of analyzed indexes on
> primary key columns.
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