Support self-join and simultaneous updates of tables

[yugo-n]

This fix allows:

• self-join views
• simultaneous updates of more than one tables
• multiple updates of the same table

This is implemented by:

• collecting transition table tuplestores in AFTER trigger
• prolonging life span of these tuplestores in trigger.c
• using BEFORE trigger and global information to handle multiple AFTER trigger invokes all at once.
• calculating pre-state of tables by using xmin, cmin and transition tables
• rewriting view definition query, calculating view deltas, and applying these to the view, for each table updates

I will write more detailed commit log message later.

Issue #5

[yugo-n]

There are no regression test yet, so I also will write this. I confirmed that all existing regression test passed.

Here re results of simple tests I performed for this patch:

CREATE TABLE r (i int, v int);
CREATE TABLE
CREATE TABLE s (i int, v int);
CREATE TABLE
CREATE TABLE t (i int, v int);
CREATE TABLE
INSERT INTO r VALUES (1, 10), (2, 20), (3, 30);
INSERT 0 3
INSERT INTO s VALUES (1, 100), (2, 200), (3, 300);
INSERT 0 3
INSERT INTO t VALUES (1, 10), (2, 20), (3, 30);
INSERT 0 3
CREATE INCREMENTAL MATERIALIZED VIEW mv_self(v1, v2) AS
 SELECT t1.v, t2.v FROM t t1 JOIN t t2 ON t1.i = t2.i;
SELECT 3
CREATE VIEW v_self(v1, v2) AS
 SELECT t1.v, t2.v FROM t t1 JOIN t t2 ON t1.i = t2.i;
CREATE VIEW
CREATE INCREMENTAL MATERIALIZED VIEW mv(v1, v2) AS
 SELECT r.v, s.v FROM r JOIN s USING(i);
SELECT 3
CREATE VIEW v(v1, v2) AS
 SELECT r.v, s.v FROM r JOIN s USING(i);
CREATE VIEW
SELECT * FROM mv_self ORDER BY v1;
 v1 | v2 
----+----
 10 | 10
 20 | 20
 30 | 30
(3 rows)

SELECT * FROM mv ORDER BY v1;
 v1 | v2  
----+-----
 10 | 100
 20 | 200
 30 | 300
(3 rows)

INSERT INTO t VALUES (4,40);
INSERT 0 1
DELETE FROM t WHERE i = 1;
DELETE 1
UPDATE t SET v = v*10 WHERE i=2;
UPDATE 1
SELECT * FROM mv_self ORDER BY v1;
 v1  | v2  
-----+-----
  30 |  30
  40 |  40
 200 | 200
(3 rows)

SELECT * FROM v_self ORDER BY v1;
 v1  | v2  
-----+-----
  30 |  30
  40 |  40
 200 | 200
(3 rows)

WITH
 ins_r AS (INSERT INTO r VALUES (1,11) RETURNING 1),
 ins_r2 AS (INSERT INTO r VALUES (3,33) RETURNING 1),
 ins_s AS (INSERT INTO s VALUES (2,222) RETURNING 1),
 upd_r AS (UPDATE r SET v = v + 1000 WHERE i = 2 RETURNING 1),
 dlt_s AS (DELETE FROM s WHERE i = 3 RETURNING 1)
SELECT NULL;
 ?column? 
----------

(1 row)

SELECT * FROM mv ORDER BY v1;
  v1  | v2  
------+-----
   10 | 100
   11 | 100
 1020 | 200
 1020 | 222
(4 rows)

SELECT * FROM v ORDER BY v1;
  v1  | v2  
------+-----
   10 | 100
   11 | 100
 1020 | 200
 1020 | 222
(4 rows)

[yugo-n]

I will write more detailed commit log message later.

So, please do not merge this PR yet. I made this PR for the just purpose of sharing current status.

[yugo-n]

I fixed some bugs and add regression tests. I also confirmed all existing regression tests passed.