-- PostgreSQL 10.1
CREATE TABLE test_bytea(test_bytea_id serial PRIMARY KEY, some_blob bytea NOT NULL);
INSERT INTO test_bytea(some_blob)
SELECT CAST(repeat('012345678901', 50000000) AS bytea);

> pg_dump -t test_bytea -f test_bytea.dump
pg_dump: Dumping the contents of table "test_bytea" failed: PQgetResult() failed.
pg_dump: Error message from server: ERROR:  invalid memory alloc request size 1200000003
pg_dump: The command was: COPY public.test_bytea (test_bytea_id, some_blob) TO stdout;