From: | Miroslav Šimulčík <simulcik(dot)miro(at)gmail(dot)com> |
---|---|
To: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
Cc: | Misa Simic <misa(dot)simic(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: function for setting/getting same timestamp during whole transaction |
Date: | 2013-02-06 12:06:18 |
Message-ID: | CAHRNM69nMnxxyoQ6C99hh6vJuepAtqXwARomN=nVb6Pmvdyc=g@mail.gmail.com |
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Lists: | pgsql-general pgsql-hackers |
>
> probably you can use a little bit cheaper session variables
>
I rejected session variables, because they don't get cleared at the end of
transaction if somebody set value on session level. So I can't decide if
new transaction started.
this is good (variable is cleared at the end of transaction):
begin;
set local test.value to 123;
show test.value;
test.value
------------
123
commit;
show test.value; --cleared => transaction ended
test.haha
-----------
but this is bad:
begin;
set local test.value to 123;
show test.value;
test.value
------------
123
set test.value to 456;
commit;
show test.value; --not cleared
test.haha
-----------
456
> test to system tables is slower then trapping error - just try to read
> from tmp and when a read fails, then create table
>
Ok I will try reading from temp table directly with error trapping and
compare times.
> probably C trigger can be very effective, possible to use this
> technique - http://postgres.cz/wiki/Funkce_rownum%28%29 (sorry, it is
> in Czech language)
>
I'm from Slovakia so I don't have problem with czech language, but I'm not
sure how to do it in C function without using temp table, because I need to
clear variable at the end/start of transaction. Any hints?
Miro
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