ср, 18 июл. 2018 г. в 15:34, Nikita Tatunov <hollow653@xxxxxxxxx>:
Hello, Alexander! Please consider changes to the patch:I tried to test that problem on this sqlite3 version with -DSQLITE_DEBUG
вт, 17 июл. 2018 г. в 16:59, Alexander Turenko <
alexander.turenko@xxxxxxxxxxxxx>:
Hi Nikita!Fixed:
Please, consider comments below.
WBR, Alexander Turenko.
On Mon, Jul 02, 2018 at 03:11:40PM +0300, N.Tatunov wrote:
To optimize the select-subquery tarantool uses
subquery flattening function which is only used
with respect to some restrictions. One of them
was implemented improperly.
Be certain: 'some restriction' and just 'improperly' are not good
problem descriptions.
I would use wording like the following.
When a subquery is a compound select the subquery flattening
optimization verify whether the ORDER BY clause presents, but only for
the last subquery component. The commit fixes that to verify all
subquery components.
In case of ORDER BY in non-last component of a compound select the
error should be raised. Accepting of such subqueries for the
flattening optimization prevents the error to be raised afterwards.
Instead it stuck into assertion violation inside flattenSubquery (see
the issue).
To optimize the select-subquery tarantool uses
subquery flattening optimization which is only used
with respect to some restrictions. When any of
subselects but the last one has an ORDER BY
clause we should raise an error. So subquery
components containing it are not accepted
to be optimized.
Checking part was only checking if the last
subselect contains the clause which led to an
assertion fail. With the patch applied
flattening is not used in case any of
subselects has an ORDER BY.
I checked sqlite3 check-in 8000d230 (it is immediate predecessor of
c9104b59 where the flattening optimization seems to be changed, but
tarantool didn't updated with that check-in). It has the assert, but has
no a change like yours, and correctly shows the following error:
Error: ORDER BY clause should come after UNION ALL not before
Why it is so?
+test:do_catchsql_test(
+ "subquery-9.3",
+ [[
+ SELECT * FROM (SELECT * FROM table1 ORDER BY 1 UNION All
+ SELECT * FROM table1 UNION All
+ SELECT * FROM table1);
All -> ALL
Also fixed.
