[YSQL] ON CONFLICT DO UPDATE with arrays on temp table

[jaki]

Jira Link: DB-1858
The non-temporary table examples below are taken from the Postgres regress test arrays.

create table arr_pk_tbl (pk int4 primary key, f1 int[]);
insert into arr_pk_tbl values (1, '{1,2,3}');
insert into arr_pk_tbl values (1, '{3,4,5}') on conflict (pk)
  do update set f1[1] = excluded.f1[1], f1[3] = excluded.f1[3]
  returning pk, f1;

outputs

 pk |   f1
----+---------
  1 | {3,2,5}
(1 row)

as expected. However, when changing it to a temporary table,

create temp table arr_pk_tbl (pk int4 primary key, f1 int[]);
insert into arr_pk_tbl values (1, '{1,2,3}');
insert into arr_pk_tbl values (1, '{3,4,5}') on conflict (pk)
  do update set f1[1] = excluded.f1[1], f1[3] = excluded.f1[3]
  returning pk, f1;

outputs

 pk |   f1
----+---------
  1 | {3,4,5}
(1 row)

which is incorrect.

Similarly, we have

insert into arr_pk_tbl(pk, f1[1:2]) values (1, '{6,7,8}') on conflict (pk)
  do update set f1[1] = excluded.f1[1],
    f1[2] = excluded.f1[2],
    f1[3] = excluded.f1[3]
  returning pk, f1;

outputting

 pk |     f1
----+------------
  1 | {6,7,NULL}
(1 row)

on non-temporary table but outputting

 pk |  f1
----+-------
  1 | {6,7}
(1 row)

on temporary table, again incorrect.