Support ON CONFLICT DO NOTHING

Currently, we already Support on conflict do nothing like postgres_fdw. I would like to contribute them into repository and community. If you have interest? I will create pull request for share this feature.

Summary modification:

Only DO_NOTHING is supported without an inference specification. update mysql_deparse_insert() for DO_NOTHING case

Reference testcase of postgres_fdw.sql in postgres_fdw:

-- On MySQL server
mysql -h $MYSQL_HOST -u $MYSQL_USER_NAME -D $MYSQL_PORT -D mysql_fdw_post -e "CREATE TABLE t1_constraint (c1 int primary key, c2 int NOT NULL check (c2 >= 0), c3 text, c4 timestamp, c5 timestamp, c6 varchar(10), c7 char(10), c8 text check (c8 IN ('foo','bar', 'buz')));"

'-- On PostgreSQL server
CREATE FOREIGN TABLE ft1_constraint (
    c1 int OPTIONS (key 'true'),
    c2 int NOT NULL,
    c3 text,
    c4 timestamp,
    c5 timestamp,
    c6 varchar(10),
    c7 char(10) default 'ft1',
    c8 text
) SERVER mysql_svr OPTIONS (dbname 'mysql_fdw_post', table_name 't1_constraint');

INSERT INTO ft1_constraint SELECT * FROM ft1 ON CONFLICT DO NOTHING; -- c2 must be greater than or equal to 0, so this case is ignored.

INSERT INTO ft1_constraint(c1, c2) VALUES (2222, -2) ON CONFLICT DO NOTHING; -- ignore, do nothing

SELECT c1, c2 FROM ft1_constraint WHERE c1 = 2222 or c2 = -2; -- empty result
 c1 | c2 
----+----
(0 rows)

EnterpriseDB / mysql_fdw

Support ON CONFLICT DO NOTHING #246