Liquibase: Implement fix for handling primary keys with DESC columns

[rafiss]

See the Slack thread for more info: https://cockroachlabs.slack.com/archives/CUG42HAN9/p1590500097054500

Dataical has added a cockroachdb-support branch that has a CockroachDatabase class.

When using Liquibase to make a table definition like this in CockroachDB, it errors out.

CREATE TABLE "order" (
  o_id INT8 NOT NULL,
  o_d_id INT8 NOT NULL,
  o_w_id INT8 NOT NULL,
  o_c_id INT8 NULL,
  o_entry_d TIMESTAMP NULL,
  o_carrier_id INT8 NULL,
  o_ol_cnt INT8 NULL,
  o_all_local INT8 NULL,
  CONSTRAINT "primary" PRIMARY KEY (o_w_id ASC, o_d_id ASC, o_id DESC),
  UNIQUE INDEX order_idx (o_w_id ASC, o_d_id ASC, o_c_id ASC, o_id DESC) STORING (o_entry_d, o_carrier_id),
  FAMILY "primary" (o_id, o_d_id, o_w_id, o_c_id, o_entry_d, o_carrier_id, o_ol_cnt, o_all_local)
)

You see how it is creating a PK with o_id DESC. This is cockroach-specific syntax not available in regular postgresql. In postgresql, you can only create primary keys with asc columns. Our generic postgresql support doesn’t have support for WITH INDEX primary keys like we do for other databases, I’m not sure if that is a good fit for this fix or not, though.

[rafiss]

will be fixed by liquibase/liquibase#1319