PostgreSQL UNIQUE constraint error message On Appendix A: PostgreSQL error codes, it says:


  For some types of errors, the server reports the name of a database object (a table, table column, data type, or constraint) associated with the error; for example, the name of the unique constraint that caused a unique_violation error. Such names are supplied in separate fields of the error report message so that applications need not try to extract them from the possibly-localized human-readable text of the message.


Bold emphasis mine. I have the following table:

CREATE TABLE recipes (
    id SERIAL,
    title TEXT UNIQUE NOT NULL,
    description TEXT NOT NULL,
    instructions TEXT NOT NULL,
    image BYTEA,
    CONSTRAINT recipes_pk PRIMARY KEY(id),
    CONSTRAINT title_unique UNIQUE(title)
);


When I try to insert a new row with a duplicate title, I get the following error message in pgAdmin3:

ERROR:  duplicate key value violates unique constraint "title_unique"
DETAIL:  Key (title)=(mytitle) already exists.


Or, using PHP:

["errorInfo"]=&gt;
  array(3) {
    [0]=&gt;
    string(5) "23505"
    [1]=&gt;
    int(7)
    [2]=&gt;
    string(117) "ERROR:  duplicate key value violates unique constraint "title_unique"
                 DETAIL:  Key (title)=(mytitle) already exists."
  }


According to the paragraph from the PostgreSQL documentation, shouldn't the constraint name title_unique be found in a separate field of the error info?

I'm using PostgreSQL 9.4.5.
For instance, you can read these separate fields mentioned in your quote inside exception handlers in PL/pgSQL (as instructed in the manual, like @dezso commented):

DO
$$
DECLARE
   err_constraint text;

BEGIN
   INSERT INTO recipes (title) VALUES ('foo'), ('foo');  -- provoke unique violation

EXCEPTION
   WHEN SQLSTATE '23000' THEN  -- Class 23 — Integrity Constraint Violation
      GET STACKED DIAGNOSTICS err_constraint = CONSTRAINT_NAME;
      -- do something with it, for instance:
      RAISE NOTICE '%', err_constraint;
      RAISE;  -- raise original error

END;
$$


Result:

NOTICE:  title_unique

ERROR:  duplicate key value violates unique constraint "title_unique"
DETAIL:  Key (title)=(foo) already exists.
CONTEXT:  SQL statement "INSERT INTO recipes (title) VALUES ('foo')"
PL/pgSQL function inline_code_block line 5 at SQL statement

Aside: you declare the unique constraints twice in your DDL command. (To my surprise, this results in a single constraint in my test on pg 9.5). Either way, do it only once.

CREATE TABLE recipes (
    id SERIAL,
    title TEXT NOT NULL,  -- remove redundant clause
    description TEXT NOT NULL,
    instructions TEXT NOT NULL,
    image BYTEA,
    CONSTRAINT recipes_pk PRIMARY KEY(id),
    CONSTRAINT title_unique UNIQUE(title)
);