Re: SQL:2011 application time

one more minor issue related to error reporting.
I've only applied v28, 0001 to 0005.

-- (parent_id, valid_at) REFERENCES [implicit]
-- FOREIGN KEY part should specify PERIOD
CREATE TABLE temporal_fk_rng2rng (
id int4range,
valid_at daterange,
parent_id int4range,
CONSTRAINT temporal_fk_rng2rng_pk PRIMARY KEY (id, valid_at WITHOUT OVERLAPS),
CONSTRAINT temporal_fk_rng2rng_fk FOREIGN KEY (parent_id, valid_at)
REFERENCES temporal_rng
);
ERROR: number of referencing and referenced columns for foreign key disagree

-- (parent_id, PERIOD valid_at) REFERENCES (id)
CREATE TABLE temporal_fk_rng2rng (
id int4range,
valid_at daterange,
parent_id int4range,
CONSTRAINT temporal_fk_rng2rng_pk PRIMARY KEY (id, valid_at WITHOUT OVERLAPS),
CONSTRAINT temporal_fk_rng2rng_fk FOREIGN KEY (parent_id, PERIOD valid_at)
REFERENCES temporal_rng (id)
);
ERROR: foreign key uses PERIOD on the referencing table but not the
referenced table

these error messages seem somehow inconsistent with the comments above?

+ else
+ {
+ /*
+ * Check it's a btree; currently this can never fail since no other
+ * index AMs support unique indexes. If we ever did have other types
+ * of unique indexes, we'd need a way to determine which operator
+ * strategy number is equality. (Is it reasonable to insist that
+ * every such index AM use btree's number for equality?)
+ */
+ if (amid != BTREE_AM_OID)
+ elog(ERROR, "only b-tree indexes are supported for foreign keys");
+ eqstrategy = BTEqualStrategyNumber;
+ }

the comments say never fail.
but it actually failed. see:

+-- (parent_id) REFERENCES [implicit]
+-- This finds the PK (omitting the WITHOUT OVERLAPS element),
+-- but it's not a b-tree index, so it fails anyway.
+-- Anyway it must fail because the two sides have a different
definition of "unique".
+CREATE TABLE temporal_fk_rng2rng (
+ id int4range,
+ valid_at daterange,
+ parent_id int4range,
+ CONSTRAINT temporal_fk_rng2rng_pk PRIMARY KEY (id, valid_at WITHOUT OVERLAPS),
+ CONSTRAINT temporal_fk_rng2rng_fk FOREIGN KEY (parent_id)
+ REFERENCES temporal_rng
+);
+ERROR: only b-tree indexes are supported for foreign keys

because in transformFkeyGetPrimaryKey.
we have `if (indexStruct->indisexclusion && i == indexStruct->indnatts - 1)`
we have pk_with_period, fk_with_period in Constraint struct.

maybe we can add a bool argument to transformFkeyGetPrimaryKey
indicate, this primary key is a conperiod constraint.
then we can check condition: the primary key is a conperiod constraint
and fk_with_period or is pk_with_period is false

I've made a patch to make these error reporting more accurate.
you can further refine it.