psql SQL Interpolation in a code block - postgresql

Question

In some of my scripts I use SQL Interpolation feature of psql utility:
basic.sql:
update :schema.mytable set ok = true;
> psql -h 10.0.0.1 -U postgres -f basic.sql -v schema=myschema
Now I need bit more complicated scenario. I need to specify schema name (and desirebly some other things) inside PL/pgSQL code block:
pg.sql
do
$$
begin
update :schema.mytable set ok = true;
end;
$$
But unfortunately this does not work, since psql does not replace :variables inside $$.
Is there a way to workaround it in general? Or more specifically, how to substitute schema names into pgSQL code block or function definition?

Answer 1

in your referenced docs:
Variable interpolation will not be performed within quoted SQL
literals and identifiers. Therefore, a construction such as ':foo'
doesn't work to produce a quoted literal from a variable's value (and
it would be unsafe if it did work, since it wouldn't correctly handle
quotes embedded in the value).
it does not matter if quotes are double dollar sign or single quote - it wont work, eg:
do
'
begin
update :schema.mytable set ok = true;
end;
'
ERROR: syntax error at or near ":"
to pass variable into quoted statement other way you can try using shell variables, eg:
MacBook-Air:~ vao$ cat do.sh; export schema_name='smth' && bash do.sh
psql -X so <<EOF
\dn+
do
\$\$
begin
execute format ('create schema %I','$schema_name');
end;
\$\$
;
\dn+
EOF
List of schemas
Name | Owner | Access privileges | Description
----------+----------+-------------------+------------------------
public | vao | vao=UC/vao +| standard public schema
| | =UC/vao |
schema_a | user_old | |
(2 rows)
DO
List of schemas
Name | Owner | Access privileges | Description
----------+----------+-------------------+------------------------
public | vao | vao=UC/vao +| standard public schema
| | =UC/vao |
schema_a | user_old | |
smth | vao | |
(3 rows)