Question

Is there some way to do a INSERT INTO t1 SELECT * FROM... such that it fails if the column names do not coincide?

I’m using Postgresql 9.x The columns names are not known in advance.

Motivation: I’m doing a periodic refresh of materialized views by the (quite standard) PL/pgSQL procedure:

CREATE OR REPLACE FUNCTION matview_refresh(name) RETURNS void AS 
$BODY$
DECLARE 
    matview ALIAS FOR $1;
    entry matviews%ROWTYPE;
BEGIN
    SELECT * INTO entry FROM matviews WHERE mv_name = matview;
    IF NOT FOUND THEN
        RAISE EXCEPTION 'Materialized view % does not exist.', matview;
    END IF;

    EXECUTE 'TRUNCATE TABLE ' || matview;
    EXECUTE 'INSERT INTO ' || matview  || ' SELECT * FROM ' || entry.v_name;

    UPDATE matviews SET last_refresh=CURRENT_TIMESTAMP WHERE mv_name=matview;
    RETURN;
END

I preferred a TRUNCATE followed by a SELECT * INTO instead of a DROP/CREATE because it seemed more light and concurrent-friendly. It would fail if someone adds/remove columns from the view (then I would do the DROP/CREATE) but, it doesn’t matter, in that case the refresh would not complete and we would catch the problem soon. What does matter is what happened today: someone changed the order of two columns of the view (of the same type), and the refresh inserted bogus data.

Answer 1

Build this into your plpgsql function to verify that view and table share the same column names in the same sequence exactly:

IF EXISTS (
    SELECT 1
    FROM (
       SELECT *
       FROM   pg_attribute
       WHERE  attrelid = matview::regclass
       AND    attisdropped = FALSE
       AND    attnum > 0
       ) t
    FULL OUTER JOIN (
       SELECT *
       FROM   pg_attribute
       WHERE  attrelid = entry.v_name::regclass
       AND    attisdropped = FALSE
       AND    attnum > 0
       ) v USING (attnum, attname) -- atttypid to check for type, too
    WHERE t.attname IS NULL
    OR    v.attname IS NULL
   ) THEN 
   RAISE EXCEPTION 'Mismatch between table and view!';
END IF;

The FULL OUTER JOIN adds a row with NULL values for any mismatch between the list of column names. So, if EXISTS finds a row, something is off.

And the cast to ::regclass would raise an exception right away if either table or view do not exist (or is out of scope – not in the search_path and not schema-qualified).

If you also want to check data types of the columns, just add atttypid to the USING clause.

As an aside: Querying pg_catalog tables is regularly faster by an order of magnitude than querying the bloated views int information_schema – information_schema is only good for SQL standard compliance and portability of code. Since you are writing 100 % Postgres-specific code, neither is relevant here.