Partition the package_derivations_by_guix_revision_range table

And create a proper git_branches table in the process.

I'm hoping this will help with slow deletions from the
package_derivations_by_guix_revision_range table in the case where there are
lots of branches, since it'll separate the data for one branch from another.

These migrations will remove the existing data, so
rebuild-package-derivations-table will currently need manually running to
regenerate it.

sqitch/deploy/git_branch_id.sql

@@ -0,0 +1,32 @@
+-- Deploy guix-data-service:git_branch_id to pg
+
+BEGIN;
+
+ALTER TABLE git_branches RENAME TO git_branches_old;
+
+CREATE TABLE git_branches (
+    id integer PRIMARY KEY GENERATED ALWAYS AS IDENTITY,
+    name character varying NOT NULL,
+    git_repository_id integer NOT NULL REFERENCES git_repositories (id),
+    CONSTRAINT git_repository_id_name_unique UNIQUE (git_repository_id, name)
+);
+
+CREATE TABLE git_commits (
+    id integer PRIMARY KEY GENERATED ALWAYS AS IDENTITY,
+    commit character varying NOT NULL,
+    git_branch_id integer NOT NULL REFERENCES git_branches (id),
+    datetime timestamp without time zone NOT NULL
+);
+
+INSERT INTO git_branches (name, git_repository_id)
+  SELECT DISTINCT name, git_repository_id
+  FROM git_branches_old;
+
+INSERT INTO git_commits (commit, git_branch_id, datetime)
+  SELECT commit, git_branches.id, datetime
+  FROM git_branches_old
+  INNER JOIN git_branches
+    ON git_branches_old.name = git_branches.name
+   AND git_branches_old.git_repository_id = git_branches.git_repository_id;
+
+COMMIT;

sqitch/deploy/partition_package_derivations_by_guix_revision_range.sql

@@ -0,0 +1,18 @@
+-- Deploy guix-data-service:partition_package_derivations_by_guix_revision_range to pg
+
+BEGIN;
+
+DROP TABLE package_derivations_by_guix_revision_range;
+
+CREATE TABLE package_derivations_by_guix_revision_range (
+  git_branch_id integer NOT NULL REFERENCES git_branches (id),
+  package_name varchar NOT NULL,
+  package_version varchar NOT NULL,
+  derivation_id integer NOT NULL,
+  system varchar NOT NULL,
+  target varchar NOT NULL,
+  first_guix_revision_id integer NOT NULL REFERENCES guix_revisions (id),
+  last_guix_revision_id integer NOT NULL REFERENCES guix_revisions (id)
+) PARTITION BY LIST (git_branch_id);
+
+COMMIT;

sqitch/revert/git_branch_id.sql

@@ -0,0 +1,7 @@
+-- Revert guix-data-service:git_branch_id from pg
+
+BEGIN;
+
+-- XXX Add DDLs here.
+
+COMMIT;

sqitch/revert/partition_package_derivations_by_guix_revision_range.sql

@@ -0,0 +1,7 @@
+-- Revert guix-data-service:partition_package_derivations_by_guix_revision_range from pg
+
+BEGIN;
+
+-- XXX Add DDLs here.
+
+COMMIT;

sqitch/sqitch.plan

@@ -83,3 +83,5 @@ some_indexes 2021-05-17T17:36:38Z Christopher Baines <mail@cbaines.net> # Add so
 package_metadata_location_id_index 2021-05-27T19:51:13Z Canan Talayhan <canan.t.talayhan@gmail.com> # Add index for location id
 packages_replacement 2021-04-24T04:52:57Z Christopher Baines <mail@cbaines.net> # Add packages.replacement_package_id
 package_derivations_not_null_hash_index 2021-07-11T14:19:32Z Christopher Baines <mail@cbaines.net> # Add an index to package_derivations
+git_branch_id 2022-05-23T18:11:14Z Chris <chris@felis> # Add git_branch.id
+partition_package_derivations_by_guix_revision_range 2022-05-23T18:20:37Z Chris <chris@felis> # Partition package_derivations_by_guix_revision_range

sqitch/verify/git_branch_id.sql

@@ -0,0 +1,7 @@
+-- Verify guix-data-service:git_branch_id on pg
+
+BEGIN;
+
+-- XXX Add verifications here.
+
+ROLLBACK;

sqitch/verify/partition_package_derivations_by_guix_revision_range.sql

@@ -0,0 +1,7 @@
+-- Verify guix-data-service:partition_package_derivations_by_guix_revision_range on pg
+
+BEGIN;
+
+-- XXX Add verifications here.
+
+ROLLBACK;