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help / color / mirror / Atom feedFrom: Pavel Stehule <pavel.stehule@gmail.com>
To: Pavel Luzanov <p.luzanov@postgrespro.ru>
Cc: David G. Johnston <david.g.johnston@gmail.com>
Cc: Pavel Golub <pavel@gf.microolap.com>
Cc: PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] proposal: schema variables
Date: Mon, 12 Mar 2018 07:54:26 +0100
Message-ID: <CAFj8pRDLBtPM9PAVx-VFtLyZJktKL5R4hX4V4O4KvcyjbOPRbw@mail.gmail.com> (raw)
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<dde8f23f-a15f-e88b-482e-5c26cce14cca@postgrespro.ru>
2018-03-12 7:49 GMT+01:00 Pavel Luzanov <p.luzanov@postgrespro.ru>:
> Hi,
>
> I plan to make usability and feature test review in several days.
>
> Is there any chances that it will work on replicas?
> Such possibility is very helpful in generating reports.
> Now, LET command produces an error:
>
> ERROR: cannot execute LET in a read-only transaction
>
>
> But if we say that variables are non-transactional ?
>
sure, it should to work. Now, I am try to solve a issues on concept level -
the LET code is based on DML code base, so probably there is check for rw
transactions. But it is useless for LET command.
Regards
Pavel
>
> -----
> Pavel Luzanov
> Postgres Professional: http://www.postgrespro.com
> The Russian Postgres Company
>
> On 08.03.2018 21:00, Pavel Stehule wrote:
>
> Hi
>
> 2018-02-07 7:34 GMT+01:00 Pavel Stehule <pavel.stehule@gmail.com>:
>
>> Hi
>>
>> updated patch with your changes in documentation and pg_dump (initial)
>> support
>>
>> Main issue of this patch is storage. We can reuse local buffers used for
>> temp tables. But it does allocation by 8KB and it creates temp files for
>> every object. That is too big overhead. Storing just in session memory is
>> too simple - then there should be lot of new code used, when variable will
>> be dropped.
>>
>> I have ideas how to allow work with mix of scalar and composite types -
>> so it will be next step of this prototype.
>>
>> Regards
>>
>> Pavel
>>
>
> new update - rebased, + some initial support for composite values on right
> side and custom types, arrays are supported too.
>
> omega=# CREATE VARIABLE xx AS (a int, b numeric);
> CREATE VARIABLE
> omega=# LET xx = (10, 20)::xx;
> LET
> omega=# SELECT xx;
> +---------+
> | xx |
> +---------+
> | (10,20) |
> +---------+
> (1 row)
>
> omega=# SELECT xx.a + xx.b;
> +----------+
> | ?column? |
> +----------+
> | 30 |
> +----------+
> (1 row)
>
> omega=# \d xx
> schema variable "public.xx"
> +--------+---------+
> | Column | Type |
> +--------+---------+
> | a | integer |
> | b | numeric |
> +--------+---------+
>
>
> Regards
>
> Pavel
>
>
>
>
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Subject: Re: [HACKERS] proposal: schema variables
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