Implement search with PostgreSQL trigrams

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

Rename function to reflect that we only get one result

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

Add loggers and make Ecto call parallels during search

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

Implement trigrams for events & replace pg similarity operator % with <%

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

Fix tests

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

priv/repo/migrations/20180109150000_prerequites.exs

@@ -2,6 +2,15 @@ defmodule Mobilizon.Repo.Migrations.Prerequites do
   use Ecto.Migration
 
   def up do
+    IO.puts("\n
+    #########################################################
+    # If the CREATE EXTENSION or DROP EXTENSION calls fail, #
+    # please manually execute them with an authorized       #
+    # PostgreSQL user with SUPER USER role.                 #
+    #########################################################
+    \n
+    ")
+
     execute("""
     CREATE TYPE datetimetz AS (
         dt timestamptz,
@@ -10,10 +19,23 @@ defmodule Mobilizon.Repo.Migrations.Prerequites do
     """)
 
     execute("CREATE EXTENSION IF NOT EXISTS postgis")
+    execute("CREATE EXTENSION IF NOT EXISTS pg_trgm")
+    execute("CREATE EXTENSION IF NOT EXISTS unaccent")
   end
 
   def down do
+    IO.puts("\n
+    #########################################################
+    # If the CREATE EXTENSION or DROP EXTENSION calls fail, #
+    # please manually execute them with an authorized       #
+    # PostgreSQL user with SUPER USER role.                 #
+    #########################################################
+    \n
+    ")
+
     execute("DROP TYPE IF EXISTS datetimetz;")
     execute("DROP EXTENSION IF EXISTS postgis")
+    execute("DROP EXTENSION IF EXISTS pg_trgm")
+    execute("DROP EXTENSION IF EXISTS unaccent")
   end
 end