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e6ca7ca14d
Since IMPALA-6314 on runtime scalar subqueries we set LIMIT 2
in StmtRewriter.mergeExpr(). We do that because later we add a
CardinalityCheckNode on top of such subqueries and with
LIMIT 2 we can still check if they return more than one row.
In the constructor of CardinalityCheckNode there is a
precondition that checks if the child node has LIMIT 2 to
be certain that we've set the limit for all the necessary
cases.
However, some subqueries will get a LIMIT 1 later breaking the
precondition in CardinalityCheckNode. An example to these
subqueries is a select stmt that selects from an inline view
that returns a single row:
select * from functional.alltypes
where int_col = (select f.id from (
select * from functional.alltypes limit 1) f);
Note that we shouldn't add a CardinalityCheckNode to the plan
of this query in the first place. To generate a proper plan I
updated SelectStmt.returnsSingleRow() because this method didn't
handle this case well.
I also changed
the precondition from
Preconditions.checkState(child.getLimit() == 2);
to
Preconditions.checkState(child.getLimit() <= 2);
in order to be more permissive.
I added tests for the aforementioned query.
Change-Id: I82a7a3fe26db3e12131c030c4ad055a9c4955407
Reviewed-on: http://gerrit.cloudera.org:8080/10605
Reviewed-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>