Hello I worked on simple patch, that enable access from server side to client side data. It add two new hooks to libpq - one for returning of local context, second for setting of local context.
A motivation is integration of possibilities of psql console together
with stronger language - plpgsql. Second target is enabling
possibility to save a result of some server side process in psql. It
improve vars feature in psql.
pavel ~/src/postgresql/src $ cat test.sql
\echo value of external paremeter is :"myvar"
do $$
begin
-- we can take any session variable on client side
-- it is safe against to SQL injection
raise notice 'external parameter accessed from plpgsql is "%"',
hgetvar('myvar');
-- we can change this session variable and finish transaction
perform hsetvar('myvar', 'Hello, World');
end;
$$ language plpgsql;
\echo new value of session variable is :"myvar"
cat test.sql | psql postgres -v myvar=Hello
value of external paremeter is "Hello"
NOTICE: external parameter accessed from plpgsql is "Hello"
DO
new value of session variable is "Hello, World"
This is just proof concept - there should be better integration with
pl languages, using cache for read on server side, ...
Notices?
Regards
Pavel Stehule
client-session-vars.diff
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