Adding a key to an empty hstore column

Question

According to the postgres documentation, you add a key to an hstore column as follows:

UPDATE tab SET h = h || (\'c\' => \'3\');

But it seem

Answer 1

To avoid this you need to ensure the hstore is created as empty and not null. You can add an empty hstore to an existing table:

ALTER TABLE htest ADD h HSTORE NOT NULL DEFAULT '';

Or you can alter your existing hstore to empty:

ALTER TABLE htest ALTER COLUMN h SET NOT NULL;
ALTER TABLE htest ALTER COLUMN h SET DEFAULT '';

Please note that exiting values cannot be null when you set the column to 'NOT NULL'.