malformed array literal - PostgreSQL

Question

I want to copy an array from jsonb field to a PostgreSQL array column:

CREATE TABLE survey_results (
    id integer NOT NULL,
    areas text[],  
    raw jsonb DEFAULT '{}'::jsonb
);

INSERT INTO survey_results (id, raw)
    VALUES (1, '{"areas": ["test", "test2"]}');

UPDATE survey_results SET areas = CAST(raw#>>'{areas}' AS text[]);

This returns me?

ERROR: malformed array literal: "["test", "test2"]" Detail: "[" must introduce explicitly-specified array dimensions.

How can I fix that?

http://sqlfiddle.com/#!17/d8122/2

Answer 1

http://sqlfiddle.com/#!17/d8122/33

json array is not self castable to postgres array. You need to either properly parse and cast it (json_array_elements, unnest, array_agg), or use some monkey hack, like:

UPDATE survey_results 
SET areas = concat('{',translate(raw#>>'{areas}','"',$$'$$),'}')::text[];

above I "prepare" json array, by changing quotes, so they would be literal, not identifier ones and prepare it to postgres array text representation '{}'

as alternative smth like:

with a as (
  select jsonb_array_elements_text(raw#>'{areas}') e from survey_results 
)
, b as (
select array_agg(e) ag from a
)
UPDATE survey_results 
SET areas = ag::text[]
FROM b;
select * from survey_results
  ;

can be used - for safer "casting"