Re: Implementing Incremental View Maintenance

As I understand it, the current patch performs immediate IVM using AFTER
STATEMENT trigger transition tables.

However, multiple tables can be modified *before* AFTER STATEMENT triggers
are fired.

CREATE TABLE example1 (a int);
CREATE TABLE example2 (a int);

CREATE INCREMENTAL MATERIALIZED VIEW mv AS
SELECT example1.a, example2.a
FROM example1 JOIN example2 ON a;

WITH
insert1 AS (INSERT INTO example1 VALUES (1)),
insert2 AS (INSERT INTO example2 VALUES (1))
SELECT NULL;

Changes to example1 are visible in an AFTER STATEMENT trigger on example2,
and vice versa. Would this not result in the (1, 1) tuple being
"double-counted"?

IVM needs to either:

(1) Evaluate deltas "serially' (e.g. EACH ROW triggers)

(2) Have simultaneous access to multiple deltas:
delta_mv = example1 x delta_example2 + example2 x delta_example1 -
delta_example1 x delta_example2

This latter method is the "logged" approach that has been discussed for
deferred evaluation.

tl;dr It seems that AFTER STATEMENT triggers required a deferred-like
implementation anyway.