Remove duplicate index on cluster_agents

changelogs/unreleased/244484-remove-redundant-cluster-agents-index.yml

+---
+title: Remove duplicate index on cluster_agents
+merge_request: 42902
+author:
+type: other

db/migrate/20200921203231_remove_duplicate_cluster_agents_index.rb

+# frozen_string_literal: true
+
+class RemoveDuplicateClusterAgentsIndex < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  INDEX = 'index_cluster_agents_on_project_id'
+
+  disable_ddl_transaction!
+
+  def up
+    remove_concurrent_index_by_name :cluster_agents, INDEX
+  end
+
+  def down
+    add_concurrent_index :cluster_agents, :project_id, name: INDEX
+  end
+end

db/schema_migrations/20200921203231

+7f62ce5117a16213bad6537dfeae2af4016262c533f8fa6b7a19572077bcf8d7
\ No newline at end of file

db/structure.sql

@@ -19789,8 +19789,6 @@ CREATE INDEX index_cluster_agent_tokens_on_agent_id ON cluster_agent_tokens USIN
 
 CREATE UNIQUE INDEX index_cluster_agent_tokens_on_token_encrypted ON cluster_agent_tokens USING btree (token_encrypted);
 
-CREATE INDEX index_cluster_agents_on_project_id ON cluster_agents USING btree (project_id);
-
 CREATE UNIQUE INDEX index_cluster_agents_on_project_id_and_name ON cluster_agents USING btree (project_id, name);
 
 CREATE UNIQUE INDEX index_cluster_groups_on_cluster_id_and_group_id ON cluster_groups USING btree (cluster_id, group_id);