Getting a violates foreign key constraint from PostgreSQL in a AFTER INSERT OR UPDATE trigger - postgresql

Question

I have two tables, documents and events. When a document is inserted or updated I would like to update the events table.
-- Create the document store table
CREATE TABLE documents (
id TEXT PRIMARY KEY,
parent TEXT REFERENCES documents,
data JSONB,
created TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT now(),
updated TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT now()
);
-- Create the normalized event table
CREATE TABLE events (
document TEXT REFERENCES documents,
type TEXT NOT NULL,
eventDate date NOT NULL,
title TEXT,
subtitle TEXT,
description TEXT,
PRIMARY KEY(document, type, eventDate)
);
I have a helper function and trigger:
-- Keep the update documentDB column valid
CREATE OR REPLACE FUNCTION update_modified_column()
RETURNS TRIGGER AS $$
BEGIN
NEW.updated = now();
RETURN NEW;
END;
$$ language 'plpgsql';
CREATE TRIGGER trigger_patents_updated BEFORE UPDATE ON documents
FOR EACH ROW EXECUTE PROCEDURE update_modified_column();
-- Put a document
CREATE OR REPLACE FUNCTION PutDocument(in_data JSON)
RETURNS TEXT AS $$
DECLARE
r_id TEXT;
BEGIN
INSERT INTO documents (id, parent, data) VALUES (in_data::JSONB->>'id',
in_data::JSONB->>'parent', in_data::JSONB)
ON CONFLICT (id) DO UPDATE SET data=in_data::JSONB RETURNING id
INTO r_id;
RETURN r_id;
END;
$$ language 'plpgsql';
Then I have the trigger that should update the events table
-- Create birthday events
CREATE OR REPLACE FUNCTION document_to_event_birthday()
RETURNS TRIGGER AS $$
BEGIN
INSERT INTO events (document, type, eventDate, title, subtitle, description)
VALUES(NEW.data->'id', 'BIRTH', to_date(NEW.data->'birth'->>'date', 'YYYY-MM-DD'), 'title', 'subtitle', 'description')
ON CONFLICT ON CONSTRAINT events_pkey DO NOTHING;
RETURN NEW;
END;
$$ LANGUAGE plpgsql;
CREATE TRIGGER document_to_event_birthday
AFTER INSERT OR UPDATE ON documents
FOR EACH ROW EXECUTE PROCEDURE document_to_event_birthday();
When I try to insert a document it errors in the document_to_event_birthday function.
PutDocument('{"id": "ham", "test": "value", "birth": { "date": "2011-06-02" }}');
Gives me
ERROR: insert or update on table "events" violates foreign key constraint "events_document_fkey"
DETAIL: Key (document)=("ham") is not present in table "documents".
CONTEXT: SQL statement "INSERT INTO events (document, type, eventDate, title, subtitle, description)
VALUES(NEW.data->'id', 'BIRTH', to_date(NEW.data->'birth'->>'date', 'YYYY-MM-DD'), 'title', 'subtitle', 'description')
ON CONFLICT ON CONSTRAINT events_pkey DO NOTHING"
PL/pgSQL function document_to_event_birthday() line 3 at SQL statement
SQL statement "INSERT INTO documents (id, parent, data) VALUES (in_data::JSONB->>'id',
in_data::JSONB->>'parent', in_data::JSONB)
ON CONFLICT (id) DO UPDATE SET data=in_data::JSONB RETURNING id"
PL/pgSQL function putdocument(json) line 5 at SQL statement
If I look at the tables after the error, they are both empty. So my trigger is not happening after the insert/update on the document table.
How do I go about fixing this?

Answer 1

You made a typo in the function document_to_event_birthday(): In
INSERT INTO events (document, ...)
VALUES (NEW.data->'id', ...)
you should have used
NEW.data->>'id'
The way the function is coded now, the function tries to insert a jsonb value, which implicitly gets converted to text. But then the value is "ham" rather than ham with additional double quotes, which violates the foreign key constraint.