On May 10, 2016, at 6:14 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Given that you're coercing both one input value and the result to text,
> I don't understand why you don't just compare the text representations.
Because sometimes the text is not equal when the casted text is. Consider
'foo'::citext = 'FOO':citext
> I'm also not very clear on what you mean by "comparing column defaults".
> A column default is an expression (in the general case anyway), not just
> a value of the type.
Yeah, the pgTAP column_default_is() function takes a string representation of an expression.
> Maybe if you'd shown us the is() function, as well as a typical usage
> of _def_is(), this would be less opaque.
Here’s is():
CREATE OR REPLACE FUNCTION is (anyelement, anyelement, text) RETURNS TEXT AS $$ DECLARE result BOOLEAN;
output TEXT; BEGIN -- Would prefer $1 IS NOT DISTINCT FROM, but that's not supported by 8.1. result :=
NOT$1 IS DISTINCT FROM $2; output := ok( result, $3 ); RETURN output || CASE result WHEN TRUE THEN '' ELSE
E'\n'|| diag( ' have: ' || CASE WHEN $1 IS NULL THEN 'NULL' ELSE $1::text END || E'\n
want: ' || CASE WHEN $2 IS NULL THEN 'NULL' ELSE $2::text END ) END; END; $$ LANGUAGE plpgsql;
_def_is() is called by another function, which effectively is:
CREATE OR REPLACE FUNCTION _cdi ( NAME, NAME, NAME, anyelement, TEXT )
RETURNS TEXT AS $$
BEGIN
RETURN _def_is( pg_catalog.pg_get_expr(d.adbin, d.adrelid), pg_catalog.format_type(a.atttypid,
a.atttypmod), $4, $5 ) FROM pg_catalog.pg_namespace n, pg_catalog.pg_class c, pg_catalog.pg_attribute a,
pg_catalog.pg_attrdef d WHERE n.oid = c.relnamespace AND c.oid = a.attrelid AND a.atthasdef AND
a.attrelid= d.adrelid AND a.attnum = d.adnum AND n.nspname = $1 AND c.relname = $2 AND a.attnum > 0
AND NOT a.attisdropped AND a.attname = $3;
END;
$$ LANGUAGE plpgsql;
That function si called like this:
_cdi( :schema, :table, :column, :default, :description );
Best,
David