Explicitly state index name for create and remove

https://gitlab.com/gitlab-org/gitlab/-/issues/223041#note_381295112

db/post_migrate/20200608203426_set_proper_lock_version_indices.rb

@@ -12,9 +12,9 @@ def up
     remove_concurrent_index :merge_requests, :lock_version, where: "lock_version IS NULL"
     remove_concurrent_index :issues, :lock_version, where: "lock_version IS NULL"
 
-    add_concurrent_index :epics, :id, where: "lock_version IS NULL"
-    add_concurrent_index :merge_requests, :id, where: "lock_version IS NULL"
-    add_concurrent_index :issues, :id, where: "lock_version IS NULL"
+    add_concurrent_index :epics, :id, where: "lock_version IS NULL", name: 'index_epics_on_id'
+    add_concurrent_index :merge_requests, :id, where: "lock_version IS NULL", name: 'index_merge_requests_on_id'
+    add_concurrent_index :issues, :id, where: "lock_version IS NULL", name: 'index_issues_on_id'
   end
 
   def down
@@ -22,8 +22,8 @@ def down
     add_concurrent_index :merge_requests, :lock_version, where: "lock_version IS NULL"
     add_concurrent_index :issues, :lock_version, where: "lock_version IS NULL"
 
-    remove_concurrent_index :epics, :id, where: "lock_version IS NULL"
-    remove_concurrent_index :merge_requests, :id, where: "lock_version IS NULL"
-    remove_concurrent_index :issues, :id, where: "lock_version IS NULL"
+    remove_concurrent_index_by_name :epics, name: 'index_epics_on_id'
+    remove_concurrent_index_by_name :merge_requests, name: 'index_merge_requests_on_id'
+    remove_concurrent_index_by_name :issues, name: 'index_issues_on_id'
   end
 end

db/post_migrate/20200608212030_lock_version_cleanup_for_epics.rb

@@ -9,10 +9,10 @@ class LockVersionCleanupForEpics < ActiveRecord::Migration[6.0]
 
   def up
     validate_not_null_constraint :epics, :lock_version
-    remove_concurrent_index :epics, :id, where: "lock_version IS NULL"
+    remove_concurrent_index_by_name :epics, name: 'index_epics_on_id'
   end
 
   def down
-    add_concurrent_index :epics, :id, where: "lock_version IS NULL"
+    add_concurrent_index :epics, :id, where: "lock_version IS NULL", name: 'index_epics_on_id'
   end
 end

db/post_migrate/20200608212435_lock_version_cleanup_for_merge_requests.rb

@@ -9,10 +9,10 @@ class LockVersionCleanupForMergeRequests < ActiveRecord::Migration[6.0]
 
   def up
     validate_not_null_constraint :merge_requests, :lock_version
-    remove_concurrent_index :merge_requests, :id, where: "lock_version IS NULL"
+    remove_concurrent_index_by_name :merge_requests, name: 'index_merge_requests_on_id'
   end
 
   def down
-    add_concurrent_index :merge_requests, :id, where: "lock_version IS NULL"
+    add_concurrent_index :merge_requests, :id, where: "lock_version IS NULL", name: 'index_merge_requests_on_id'
   end
 end

db/post_migrate/20200608212549_lock_version_cleanup_for_issues.rb

@@ -9,10 +9,10 @@ class LockVersionCleanupForIssues < ActiveRecord::Migration[6.0]
 
   def up
     validate_not_null_constraint :issues, :lock_version
-    remove_concurrent_index :issues, :id, where: "lock_version IS NULL"
+    remove_concurrent_index_by_name :issues, name: 'index_issues_on_id'
   end
 
   def down
-    add_concurrent_index :issues, :id, where: "lock_version IS NULL"
+    add_concurrent_index :issues, :id, where: "lock_version IS NULL", name: 'index_issues_on_id'
   end
 end