Enforcing constraints "two tables away"

I ran into some trouble modeling an electrical schematic in SQL.The structure I'd like to capture is

  part ←────────── pin↑↑part_inst ←───── pin_inst

where "inst" is short for "instance".

For example, I might have as a part an LM358 op-amp with pins1OUT, 1IN-, 1IN+, GND, 2IN+, 2IN-, 2OUT, and V_CC. I mightthen place this part on a schematic, creating a part_inst and 8pin_insts.

Ignoring data fields, my initial attempt at a schema was

create table parts (    part_id bigserial primary key);create table pins (    pin_id bigserial primary key,    part_id bigint not null references parts);create table part_insts (    part_inst_id bigserial primary key,    part_id bigint not null references parts);create table pin_insts (    pin_inst_id bigserial primary key,    part_inst_id bigint not null references part_insts,    pin_id bigint not null references pins);

The main problem with this schema is that a pin_inst might be tiedto a part_inst with part_id=1 but its pin has part_id=2.

I'd like to avoid this problem on the database level rather than theapplication level. So, I modified my primary keys to enforce that.I marked the changed lines with --.

create table parts (    part_id bigserial primary key);create table pins (    pin_id bigserial,                                          --    part_id bigint not null references parts,    primary key (pin_id, part_id)                              --);create table part_insts (    part_inst_id bigserial,                                    --    part_id bigint not null references parts,    primary key (part_inst_id, part_id)                        --);create table pin_insts (    pin_inst_id bigserial primary key,    part_inst_id bigint not null,                              --    pin_id bigint not null,                                    --    part_id bigint not null references parts,                  --    foreign key (part_inst_id, part_id) references part_insts, --    foreign key (pin_id, part_id) references pins              --);

My gripe with this method is that it pollutes the primary keys:Everywhere I refer to a part_inst, I need to keep track of both thepart_inst_id and the part_id. Is there another way I can go about enforcing the constraintpin_inst.part_inst.part_id = pin_inst.pin.part_id without being overly verbose?