[YSQL] Non-key columns in unique index affect constraint enforcement

[srhickma]

Summary: Adding INCLUDE (non-key) columns in a unique index affects the enforcement of uniqueness on the key columns. This should not be the case.

Reproduction Steps:

postgres=# CREATE TABLE tst (c1 int, c2 int);
CREATE TABLE
postgres=# INSERT INTO tst (c1, c2) VALUES
postgres-# (1, 1),
postgres-# (1, 2);
INSERT 0 2
postgres=# CREATE UNIQUE INDEX tst_uidx ON tst USING lsm (c1) INCLUDE (c2);
CREATE INDEX

Expected Results: It is expected that the CREATE INDEX statement will produce an error, since there are duplicate values in c1.

Note: If INCLUDE (c2) is removed, then the correct error is displayed:

postgres=# CREATE UNIQUE INDEX tst_uidx2 ON tst USING lsm (c1);
ERROR:  duplicate key value violates unique constraint "tst_uidx2"

[robertpang]

This issue is fixed in commit 3de20a3.