Remove duplicates from the guix_revisions table

sqitch/deploy/remove_guix_revision_duplicates.sql

@@ -0,0 +1,37 @@
+-- Deploy guix-data-service:remove_guix_revision_duplicates to pg
+
+BEGIN;
+
+WITH data AS (
+  SELECT unnest(old_ids) AS old, id FROM (
+    SELECT MIN(id) AS id, ARRAY_AGG(id) AS old_ids
+    FROM guix_revisions
+    GROUP BY commit, git_repository_id
+    HAVING COUNT(id) > 1
+  ) AS d2
+)
+DELETE FROM guix_revision_package_derivations
+WHERE revision_id IN (SELECT old FROM data WHERE old != id);
+
+WITH data AS (
+  SELECT unnest(old_ids) AS old, id FROM (
+    SELECT MIN(id) AS id, ARRAY_AGG(id) AS old_ids
+    FROM guix_revisions
+    GROUP BY commit, git_repository_id
+    HAVING COUNT(id) > 1
+  ) AS d2
+)
+UPDATE package_versions_by_guix_revision_range
+SET first_guix_revision_id = data.id
+FROM data
+WHERE first_guix_revision_id = data.old;
+
+DELETE FROM guix_revisions AS g WHERE id NOT IN (
+  SELECT MIN(id)
+  FROM guix_revisions
+  GROUP BY (commit, git_repository_id)
+);
+
+CREATE UNIQUE INDEX ON guix_revisions (commit, git_repository_id);
+
+COMMIT;