Horton

Re: pgbench - allow to store select results into variables

Fabien COELHO <coelho@cri.ensmp.fr>

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From: Fabien COELHO <coelho@cri.ensmp.fr>
To: Pavel Stehule <pavel.stehule@gmail.com>
Cc: PostgreSQL Developers <pgsql-hackers@postgresql.org>
Date: 2016-07-09T09:19:15Z
Lists: pgsql-hackers 
Hello Pavel,

> Why you are introducing \into and not \gset like psql does?

Good question.

The \into syntax I implemented is more generic, you can send a bunch of 
queries together and extract the results, which makes sense from a client 
perspective where reducing latency is important:

    SELECT 1, 2 \; SELECT 3;
    \into one two three

However "gset" only works on the last SELECT and if all columns have a 
name. This feature probably makes sense interactively, but for a script it 
seems more useful to allow batch processing and collect results 
afterwards.

Also a more subjective argument: I do not like the gset automagic naming 
feature. I got more inspired by PL/pgSQL and ECPG which both have an 
"into" syntax with explicit variable names that let nothing to guessing. I 
like things to be simple and explicit, hence the proposed into.

-- 
Fabien.

Commits

  1. pgbench: Remove \cset

  2. pgbench: add \cset and \gset commands

  3. Adjust pgbench to allow non-ASCII characters in variable names.

  4. Refactor script execution state machine in pgbench.

  5. Allow empty queries in pgbench.