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https://issues.apache.org/jira/browse/IMPALA-5098?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17156814#comment-17156814
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ASF subversion and git services commented on IMPALA-5098:
---------------------------------------------------------
Commit fea5dffec5bcaba5eb0be4a6aad29c03a86c2da3 in impala's branch
refs/heads/master from Tim Armstrong
[ https://gitbox.apache.org/repos/asf?p=impala.git;h=fea5dff ]
IMPALA-9924: handle single subquery in or predicate
This patch supports a subset of cases of subqueries
inside OR inside WHERE and HAVING clauses.
The approach used is to rewrite the subquery into
a many-to-one LEFT OUTER JOIN with the subquery and
then replace the subquery in the expression with a
reference to the single select list expressions of
the subquery. This works because:
* A many-to-one LEFT OUTER JOIN returns one output row
for each left input row, meaning that for every row
in the original query before the rewrite, we get
the same row plus a single matched row from the subquery
* Expressions can be rewritten to refer to a slotref from
the right side of the LEFT OUTER JOIN without affecting
semantics. E.g. an IN subquery becomes <slot> IS NOT NULL
or <operator> (<subquery>) becomes <operator> <slot>.
This does not affect SELECT list subqueries, which are
rewritten using a different mechanism that can already
support some subqueries in disjuncts.
Correlated and uncorrelated subqueries are both supported, but
various limitations are present.
Limitations:
* Only one subquery per predicate is supported. The rewriting approach
should generalize to multiple subqueries but other code needs
refactoring to handle this case.
* EXISTS and NOT EXISTS subqueries are not supported. The rewriting
approach can generalise to that, but we need to add or pick a
select list item from the subquery to check for NULL/IS NOT NULL
and a little more work is required to do that correctly.
* NOT IN is not supported because of the special NULL semantics.
* Subqueries with aggregates + grouping by are not supported because
we rely on adding distinct to select list and we don't
support distinct + aggregations because of IMPALA-5098.
Tests:
* Positive analysis tests for IN and binary predicate operators.
* Negative analysis tests for unsupported subquery operators.
* Negative analysis tests for multiple subqueries.
* Negative analysis tests for runtime scalar subqueries.
* Positive and negative analysis tests for aggregations in subquery.
* TPC-DS Query 45 planner and query tests
* Targeted planner tests for various supported queries.
* Targeted functional tests to confirm plans are executable and
return correct result. These exercise a mix of the supported
features - correlated/correlated, aggregate functions,
EXISTS/comparator, etc.
* Tests for BETWEEN predicate, which is supported as a side-effect
of being rewritten during analysis.
Change-Id: I64588992901afd7cd885419a0b7f949b0b174976
Reviewed-on: http://gerrit.cloudera.org:8080/16152
Tested-by: Impala Public Jenkins <[email protected]>
Reviewed-by: Zoltan Borok-Nagy <[email protected]>
> Correct handling of DISTINCT in the select list
> -----------------------------------------------
>
> Key: IMPALA-5098
> URL: https://issues.apache.org/jira/browse/IMPALA-5098
> Project: IMPALA
> Issue Type: Bug
> Components: Frontend
> Affects Versions: Impala 2.6.0
> Reporter: N Campbell
> Assignee: Kurt Deschler
> Priority: Critical
> Labels: ansi-sql, sql-language
>
> DB2, ORACLE and various other systems will support the following statement
> but Impala will not
> {noformat}
> [Simba][ImpalaJDBCDriver](500051) ERROR processing query/statement. Error
> Code: 0,
> SQL state: TStatus(statusCode:ERROR_STATUS, sqlState:HY000,
> errorMessage:AnalysisException: cannot combine SELECT DISTINCT with analytic
> functions
> ), Query: SELECT DISTINCT
> `sno` AS `c1`,
> `pno` AS `c2`,
> SUM(`qty`)
> OVER(
> ) AS `c3`
> FROM
> `cert`.`tsupply`
> ORDER BY
> `sno` ASC NULLS LAST,
> `pno` ASC NULLS LAST.
> {noformat}
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