Re: [HACKERS] proposal: session server side variables
От | Fabien COELHO |
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Тема | Re: [HACKERS] proposal: session server side variables |
Дата | |
Msg-id | alpine.DEB.2.20.1701011005490.15074@lancre обсуждение исходный текст |
Ответ на | Re: [HACKERS] proposal: session server side variables (Pavel Stehule <pavel.stehule@gmail.com>) |
Ответы |
Re: [HACKERS] proposal: session server side variables
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Список | pgsql-hackers |
Hello Pavel, and Happy new year! >> (1) Having some kind of variable, especially in interactive mode, allows to >>>> manipulate previous results and reuse them later, without having to >>>> resort to repeated sub-queries or to retype non trivial values. >>>> >>>> Client side psql :-variables are untyped and unescaped, thus not very >>>> convenient for this purpose. >>> >>> You can currently (ab)use user defined GUCs for this. >> >> How? It seems that I have missed the syntax to assign the result of a >> query to a user-defined guc, and to reuse it simply in a query. > postgres=# select set_config('myvar.text', (select > current_timestamp::text), false); Thanks for the pointer! The documentation is rather scarse... They are indeed session or transaction-alive. They seem to be user-private, which is good. However they are text only, casts are needed in practice as shown by your example, and I find the syntax quite unfriendly for interactive use. I'm not sure about performance. I have added a subsection about them in the wiki. -- Fabien.
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