Horton

Re: Rethinking plpgsql's assignment implementation

Pavel Stehule <pavel.stehule@gmail.com>

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From: Pavel Stehule <pavel.stehule@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Chapman Flack <chap@anastigmatix.net>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Dmitry Dolgov <9erthalion6@gmail.com>
Date: 2021-01-19T18:21:04Z
Lists: pgsql-hackers 
Hi

Now, I am testing subscribing on the jsonb feature, and I found one issue,
that is not supported by parser.

When the target is scalar, then all is ok. But we can have a plpgsql array
of jsonb values.

postgres=# do $$
declare j jsonb[];
begin
  j[1] = '{"b":"Ahoj"}';
  raise notice '%', j;
  raise notice '%', (j[1])['b'];
end
$$;
NOTICE:  {"{\"b\": \"Ahoj\"}"}
NOTICE:  "Ahoj"
DO

Parenthesis work well in expressions, but are not supported on the left
side of assignment.

postgres=# do $$
declare j jsonb[];
begin
  (j[1])['b'] = '"Ahoj"';
  raise notice '%', j;
  raise notice '%', j[1]['b'];
end
$$;
ERROR:  syntax error at or near "("
LINE 4:   (j[1])['b'] = '"Ahoj"';
          ^

Regards

Pavel

Commits

  1. Rethink the "read/write parameter" mechanism in pl/pgsql.

  2. Remove PLPGSQL_DTYPE_ARRAYELEM datum type within pl/pgsql.

  3. Re-implement pl/pgsql's expression and assignment parsing.

  4. Add the ability for the core grammar to have more than one parse target.

  5. Support subscripting of arbitrary types, not only arrays.

  6. Improve handling of array elements as getdiag_targets and cursor_variables.