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https://issues.apache.org/jira/browse/IGNITE-13021?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Yury Gerzhedovich reassigned IGNITE-13021:
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Assignee: Andrey Mashenkov
> Calcite integration. Avoid full scans for disjunctive queries.
> --------------------------------------------------------------
>
> Key: IGNITE-13021
> URL: https://issues.apache.org/jira/browse/IGNITE-13021
> Project: Ignite
> Issue Type: Improvement
> Components: sql
> Reporter: Roman Kondakov
> Assignee: Andrey Mashenkov
> Priority: Major
> Time Spent: 20m
> Remaining Estimate: 0h
>
> Currently a full table scan will be executed in the case of disjunctive
> predicate even if predicate fields are indexed. For example:
> {code:java}
> SELECT * FROM emps WHERE name='A' OR surname='B'
> {code}
> This is caused by the nature of indexes: they can return cursor bounded by
> lower and upper bounds. We can cope with it by implementing a logical rule
> for rewriting {{OR}} query to a {{UNION ALL}} query:
> {code:java}
> SELECT * FROM emps WHERE name='A'
> UNION ALL
> SELECT * FROM emps WHERE surname='B' AND LNNVL(name='A')
> {code}
> where {{LNNVL()}} function has semantics
> {code:java}
> LNNVL(name='A') == name!='A' OR name=NULL.
> {code}
> It is used to avoid expensive deduplication. This name is taken from Oracle,
> we can think of more meaningful name, or find the analog in Calcite or H2.
> See, for example, this blog post:
> [https://blogs.oracle.com/optimizer/optimizer-transformations:-or-expansion]
> for details.
> Also it is needed to check this works for {{IN}} clause with small number of
> literals (AFAIK Calcite converts large {{IN}} clauses to a join with
> {{Values}} table where N > 20).
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