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From: Vladislav Shpilevoy via Tarantool-patches <tarantool-patches@dev.tarantool.org>
To: Mergen Imeev <imeevma@tarantool.org>
Cc: tarantool-patches@dev.tarantool.org
Subject: Re: [Tarantool-patches] [PATCH v4 11/16] sql: refactor COUNT() function
Date: Mon, 11 Oct 2021 23:51:07 +0200
Message-ID: <88406fd6-2fc7-f2b8-ddbd-9757cc20b384@tarantool.org> (raw)
In-Reply-To: <20211005095537.GF55311@tarantool.org>

Thanks for the fixes!

>>> diff --git a/src/box/sql/func.c b/src/box/sql/func.c
>>> index 94ec811ef..384c68be8 100644
>>> --- a/src/box/sql/func.c
>>> +++ b/src/box/sql/func.c
>>> @@ -154,6 +154,29 @@ fin_avg(struct sql_context *ctx)
>>>  		ctx->is_aborted = true;
>>>  }
>>>  
>>> +/** Implementation of the COUNT() function. */
>>> +static void
>>> +step_count(struct sql_context *ctx, int argc, struct Mem **argv)
>>> +{
>>> +	assert(argc == 0 || argc == 1);
>>> +	if (mem_is_null(ctx->pMem))
>>> +		mem_set_uint(ctx->pMem, 0);
>>
>> Would be nice to have a 'begin' step for the aggregation
>> functions. This would allow to eliminate these 'if is null'
>> ifs in some step functions in favor of having +1 virtual 'begin'
>> call in the beginning.
>>
>> Do you think it would simplify/speed up things? If you agree,
>> could you please create a ticket for that? As 'good first issue'
>> even.
>>
>> If don't agree, then ignore this comment.
> I think this is a good idea, but I don't see a suitable way to implement it. The
> problem is that in case we receive NULL as an argument, we will have NULL in
> pMem/pOut after the first step, and we still have to call begin() again or check
> with 'if'. And there is no way to determine how much NULLs will there be.

There are functions where it does not matter. For example,
TOTAL() never returns NULL. You could initialize its
accumulator with 0 from the beginning and drop

	mem_set_double(ctx->pMem, 0.0);

from step_total() and fin_total().

The same for COUNT() and mem_set_uint(ctx->pMem, 0). We have
more functions like these AFAIR.

  reply	other threads:[~2021-10-11 21:51 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-01 12:48 [Tarantool-patches] [PATCH v4 00/16] sql: refactor aggregate functions Mergen Imeev via Tarantool-patches
2021-10-01 12:48 ` [Tarantool-patches] [PATCH v4 01/16] sql: remove MEM_Zero flag from struct MEM Mergen Imeev via Tarantool-patches
2021-10-04 21:51   ` Vladislav Shpilevoy via Tarantool-patches
2021-10-05  8:46     ` Mergen Imeev via Tarantool-patches
2021-10-05  9:42       ` Mergen Imeev via Tarantool-patches
2021-10-05 12:28         ` Mergen Imeev via Tarantool-patches
2021-10-01 12:48 ` [Tarantool-patches] [PATCH v4 02/16] sql: fix possible undefined behavior during cast Mergen Imeev via Tarantool-patches
2021-10-04 21:52   ` Vladislav Shpilevoy via Tarantool-patches
2021-10-05  9:00     ` Mergen Imeev via Tarantool-patches
2021-10-01 12:48 ` [Tarantool-patches] [PATCH v4 03/16] sql: use register P1 for number of arguments Mergen Imeev via Tarantool-patches
2021-10-01 12:48 ` [Tarantool-patches] [PATCH v4 04/16] sql: remove AggStep0 and OP_BuiltinFunction0 Mergen Imeev via Tarantool-patches
2021-10-01 12:48 ` [Tarantool-patches] [PATCH v4 05/16] sql: move collation to struct sql_context Mergen Imeev via Tarantool-patches
2021-10-01 12:48 ` [Tarantool-patches] [PATCH v4 06/16] sql: introduce mem_append() Mergen Imeev via Tarantool-patches
2021-10-04 21:52   ` Vladislav Shpilevoy via Tarantool-patches
2021-10-05  9:32     ` Mergen Imeev via Tarantool-patches
2021-10-11 21:50       ` Vladislav Shpilevoy via Tarantool-patches
2021-10-19 10:49         ` Mergen Imeev via Tarantool-patches
2021-10-01 12:48 ` [Tarantool-patches] [PATCH v4 07/16] sql: remove sql_vdbemem_finalize() Mergen Imeev via Tarantool-patches
2021-10-01 12:48 ` [Tarantool-patches] [PATCH v4 08/16] sql: refactor SUM() function Mergen Imeev via Tarantool-patches
2021-10-01 12:48 ` [Tarantool-patches] [PATCH v4 09/16] sql: refactor TOTAL() function Mergen Imeev via Tarantool-patches
2021-10-01 12:48 ` [Tarantool-patches] [PATCH v4 10/16] sql: refactor AVG() function Mergen Imeev via Tarantool-patches
2021-10-04 21:53   ` Vladislav Shpilevoy via Tarantool-patches
2021-10-05  9:48     ` Mergen Imeev via Tarantool-patches
2021-10-11 21:50       ` Vladislav Shpilevoy via Tarantool-patches
2021-10-19 11:14         ` Mergen Imeev via Tarantool-patches
2021-10-01 12:48 ` [Tarantool-patches] [PATCH v4 11/16] sql: refactor COUNT() function Mergen Imeev via Tarantool-patches
2021-10-04 21:53   ` Vladislav Shpilevoy via Tarantool-patches
2021-10-05  9:55     ` Mergen Imeev via Tarantool-patches
2021-10-11 21:51       ` Vladislav Shpilevoy via Tarantool-patches [this message]
2021-10-19 11:17         ` Mergen Imeev via Tarantool-patches
2021-10-01 12:48 ` [Tarantool-patches] [PATCH v4 12/16] sql: refactor MIN() and MAX() functions Mergen Imeev via Tarantool-patches
2021-10-04 21:54   ` Vladislav Shpilevoy via Tarantool-patches
2021-10-05 10:07     ` Mergen Imeev via Tarantool-patches
2021-10-01 12:48 ` [Tarantool-patches] [PATCH v4 13/16] sql: refactor GROUP_CONCAT() function Mergen Imeev via Tarantool-patches
2021-10-01 12:48 ` [Tarantool-patches] [PATCH v4 14/16] sql: remove copying of result in finalizers Mergen Imeev via Tarantool-patches
2021-10-01 12:48 ` [Tarantool-patches] [PATCH v4 15/16] sql: remove MEM_TYPE_AGG Mergen Imeev via Tarantool-patches
2021-10-01 12:49 ` [Tarantool-patches] [PATCH v4 16/16] sql: remove field argv from struct sql_context Mergen Imeev via Tarantool-patches
2021-10-25 20:58 ` [Tarantool-patches] [PATCH v4 00/16] sql: refactor aggregate functions Vladislav Shpilevoy via Tarantool-patches
2021-10-26 10:34 Mergen Imeev via Tarantool-patches
2021-10-26 10:34 ` [Tarantool-patches] [PATCH v4 11/16] sql: refactor COUNT() function Mergen Imeev via Tarantool-patches

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