feat(perf): contacts query performance (#7175)

* feat: use more indexable where condition

* feat: add index concurrently

* chore: update schema

* refactor: update index name

app/models/contact.rb

@@ -19,6 +19,7 @@
 #  index_contacts_on_account_id                          (account_id)
 #  index_contacts_on_lower_email_account_id              (lower((email)::text), account_id)
 #  index_contacts_on_name_email_phone_number_identifier  (name,email,phone_number,identifier) USING gin
+#  index_contacts_on_identifiable_fields                 (account_id,email,phone_number,identifier) WHERE (((email)::text <> ''::text) OR ((phone_number)::text <> ''::text) OR ((identifier)::text <> ''::text)) # rubocop:disable Layout/LineLength
 #  index_contacts_on_phone_number_and_account_id         (phone_number,account_id)
 #  uniq_email_per_account_contact                        (email,account_id) UNIQUE
 #  uniq_identifier_per_account_contact                   (identifier,account_id) UNIQUE
@@ -136,7 +137,7 @@ class Contact < ApplicationRecord
   end
 
   def self.resolved_contacts
-    where("COALESCE(NULLIF(contacts.email,''),NULLIF(contacts.phone_number,''),NULLIF(contacts.identifier,'')) IS NOT NULL")
+    where("contacts.email <> '' OR contacts.phone_number <> '' OR contacts.identifier <> ''")
   end
 
   def discard_invalid_attrs

db/migrate/20230523104139_add_partial_index_for_resolved_contacts.rb

@@ -0,0 +1,8 @@
+class AddPartialIndexForResolvedContacts < ActiveRecord::Migration[7.0]
+  disable_ddl_transaction!
+
+  def change
+    add_index :contacts, [:account_id, :email, :phone_number, :identifier], where: "(email <> '' OR phone_number <> '' OR identifier <> '')",
+                                                                            name: 'index_contacts_on_nonempty_fields', algorithm: :concurrently
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.0].define(version: 2023_05_15_051424) do
+ActiveRecord::Schema[7.0].define(version: 2023_05_23_104139) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_stat_statements"
   enable_extension "pg_trgm"
@@ -405,6 +405,7 @@ ActiveRecord::Schema[7.0].define(version: 2023_05_15_051424) do
     t.jsonb "custom_attributes", default: {}
     t.datetime "last_activity_at", precision: nil
     t.index "lower((email)::text), account_id", name: "index_contacts_on_lower_email_account_id"
+    t.index ["account_id", "email", "phone_number", "identifier"], name: "index_contacts_on_nonempty_fields", where: "(((email)::text <> ''::text) OR ((phone_number)::text <> ''::text) OR ((identifier)::text <> ''::text))"
     t.index ["account_id"], name: "index_contacts_on_account_id"
     t.index ["email", "account_id"], name: "uniq_email_per_account_contact", unique: true
     t.index ["identifier", "account_id"], name: "uniq_identifier_per_account_contact", unique: true