Draft: Enable intarray extension and create new index for traversal_ids

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== 20210908093746 EnableIntArrayExtension: migrating ==========================
-- execute("CREATE EXTENSION IF NOT EXISTS intarray")
   -> 0.0161s
== 20210908093746 EnableIntArrayExtension: migrated (0.0162s) =================

== 20210908094535 AddNamespaceTraversalIdsIntArrayIndex: migrating ============
-- transaction_open?()
   -> 0.0000s
-- index_exists?(:namespaces, :traversal_ids, {:using=>:gin, :name=>"index_namespaces_on_traversal_ids_int_array", :opclass=>{:name=>:gin__int_ops}, :algorithm=>:concurrently})
   -> 0.0090s
-- execute("SET statement_timeout TO 0")
   -> 0.0006s
-- add_index(:namespaces, :traversal_ids, {:using=>:gin, :name=>"index_namespaces_on_traversal_ids_int_array", :opclass=>{:name=>:gin__int_ops}, :algorithm=>:concurrently})
   -> 0.0042s
-- execute("RESET statement_timeout")
   -> 0.0006s
== 20210908094535 AddNamespaceTraversalIdsIntArrayIndex: migrated (0.0162s) ===

== 20210908095019 RemoveNamespaceTraversalIdsIndex: migrating =================
-- transaction_open?()
   -> 0.0000s
-- indexes(:namespaces)
   -> 0.0065s
-- remove_index(:namespaces, {:algorithm=>:concurrently, :name=>"index_namespaces_on_traversal_ids"})
   -> 0.0035s
== 20210908095019 RemoveNamespaceTraversalIdsIndex: migrated (0.0112s) ========

In postgres.ai, the creation time of this index was 1.467 min.

This change can make requests that usually times out to perform with a great time. For example:

SELECT namespaces.*
FROM
  (SELECT DISTINCT on(namespaces.id) namespaces.*
   FROM namespaces,

     (SELECT namespaces.id
      FROM namespaces
      INNER JOIN members ON namespaces.id = members.source_id
      WHERE members.type = 'GroupMember'
        AND members.source_type = 'Namespace'
        AND namespaces.type = 'Group'
        AND members.user_id = 1614863
        AND members.requested_at IS NULL
        AND (access_level >= 10)
        AND members.access_level IN (40,
                                     50)) base
   WHERE (namespaces.traversal_ids @> ARRAY[base.id])) namespaces

This query went from timing out to 1ms (query plan)

How to set up and validate locally

The index and the extensions are visible in the file structure.sql.

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