[tarantool-patches] Re: [PATCH 2/2] sql: fix code generation for aggregate in HAVING clause

[Vladislav Shpilevoy <v.shpilevoy@tarantool.org>]

Thanks for the patch! See 3 comments below.

On 21/02/2019 21:01, Nikita Pettik wrote:
> When we allowed using HAVING clause without GROUP BY (b40f2443a), one
> possible combination was forgotten to be tested:
> 
> SELECT 1 FROM te40 HAVING SUM(s1) < 0;
> 
> In other words, resulting set contains no aggregates, but HAVING does
> contain.

1. We have these tests: select5-9.10, select5-9.11, select5-9.12. They all
have no aggregates in the result set, but have in HAVING. So that was not
a problem. Problem was that we forgot to test a false condition.

> In this case no byte-code related to aggregate execution is
> emitted at all. Hence, query above equals to simple SELECT 1;
> Unfortunately, result of such query is the same when condition under
> HAVING clause is satisfied.

2. Did you mean **not** satisfied?

> To fix this behaviour, it is enough to
> indicate to byte-code generator that we should analyze aggregates not
> only in ORDER BY clauses, but also in HAVING clause.
> 
> Closes #3932
> Follow-up #2364
> ---
>   src/box/sql/resolve.c         | 10 +++++++---
>   test/sql-tap/select5.test.lua | 25 ++++++++++++++++++++++++-
>   2 files changed, 31 insertions(+), 4 deletions(-)
> 
> diff --git a/src/box/sql/resolve.c b/src/box/sql/resolve.c
> index bc208cc9d..e9a1b09f7 100644
> --- a/src/box/sql/resolve.c
> +++ b/src/box/sql/resolve.c
> @@ -1290,12 +1290,16 @@ resolveSelectStep(Walker * pWalker, Select * p)
>   				return WRC_Abort;
>   		}
>   
> -		/* If there are no aggregate functions in the result-set, and no GROUP BY
> -		 * expression, do not allow aggregates in any of the other expressions.
> +		/*
> +		 * If there are no aggregate functions in the
> +		 * result-set, and no GROUP BY or HAVING
> +		 * expression, do not allow aggregates in any
> +		 * of the other expressions.
>   		 */
>   		assert((p->selFlags & SF_Aggregate) == 0);
>   		pGroupBy = p->pGroupBy;
> -		if (pGroupBy || (sNC.ncFlags & NC_HasAgg) != 0) {
> +		if ((pGroupBy != NULL || p->pHaving != NULL) ||

3. Why do you need the braces around
"pGroupBy != NULL || p->pHaving != NULL" ?

> +		    (sNC.ncFlags & NC_HasAgg) != 0) {
>   			assert(NC_MinMaxAgg == SF_MinMaxAgg);
>   			p->selFlags |=
>   			    SF_Aggregate | (sNC.ncFlags & NC_MinMaxAgg);