search: add way to search array attributes by regex.

Add a `where_any_in_array_matches_regex` method and expose it to the API:

 * https://danbooru.donmai.us/artists?search[any_other_name_matches_regex]=^blah
 * https://danbooru.donmai.us/wiki_pages?search[any_other_name_matches_regex]=^blah
 * https://danbooru.donmai.us/saved_searches?search[any_label_matches_regex]=^blah

In SQL, this does `WHERE '^blah' ~<< ANY(other_names)`, where `~<<` is a
custom operator based on the `~` regex match operator, but with the
arguments reversed. This allows it to be used with the ANY(array) operator.

See also:

* https://stackoverflow.com/a/22101172
* https://www.postgresql.org/docs/current/sql-createfunction.html
* https://www.postgresql.org/docs/current/sql-createoperator.html
* https://www.postgresql.org/docs/current/functions-comparisons.html

app/logical/concerns/searchable.rb

@@ -92,6 +92,11 @@ module Searchable
     where("lower(#{qualified_column_for(attr)}::text)::text[] @> ARRAY[?]", values.map(&:downcase))
   end
 
+  # `~<<` is a custom Postgres operator. It's the `~` regex operator with reversed arguments.
+  def where_any_in_array_matches_regex(attr, regex, flags: "e")
+    where("? ~<< ANY(#{qualified_column_for(attr)})", "(?#{flags})#{regex}")
+  end
+
   def where_text_includes_lower(attr, values)
     where("lower(#{qualified_column_for(attr)}) IN (?)", values.map(&:downcase))
   end
@@ -340,6 +345,7 @@ module Searchable
 
   def search_array_attribute(name, type, params)
     relation = all
+    singular_name = name.to_s.singularize
 
     if params[:"#{name}_include_any"]
       items = params[:"#{name}_include_any"].to_s.scan(/[^[:space:]]+/)
@@ -369,10 +375,12 @@ module Searchable
       relation = relation.where_array_includes_any_lower(name, params[:"#{name}_include_any_lower_array"])
     elsif params[:"#{name}_include_all_lower_array"]
       relation = relation.where_array_includes_all_lower(name, params[:"#{name}_include_all_lower_array"])
+    elsif params[:"any_#{singular_name}_matches_regex"]
+      relation = relation.where_any_in_array_matches_regex(name, params[:"any_#{singular_name}_matches_regex"])
     end
 
-    if params[:"#{name.to_s.singularize}_count"]
-      relation = relation.where_array_count(name, params[:"#{name.to_s.singularize}_count"])
+    if params[:"#{singular_name}_count"]
+      relation = relation.where_array_count(name, params[:"#{singular_name}_count"])
     end
 
     relation

db/migrate/20210110015410_add_reverse_regex_operator.rb

@@ -0,0 +1,11 @@
+class AddReverseRegexOperator < ActiveRecord::Migration[6.1]
+  def up
+    execute "CREATE FUNCTION reverse_textregexeq (text, text) RETURNS boolean LANGUAGE sql IMMUTABLE PARALLEL SAFE AS $$ SELECT textregexeq($2, $1); $$"
+    execute "CREATE OPERATOR ~<< (FUNCTION = reverse_textregexeq, leftarg = text, rightarg = text)"
+  end
+
+  def down
+    execute "DROP OPERATOR ~<< (text, text)"
+    execute "DROP FUNCTION reverse_textregexeq (text, text)"
+  end
+end

db/structure.sql

@@ -352,6 +352,15 @@ CREATE FUNCTION public.favorites_insert_trigger() RETURNS trigger
       $$;
 
 
+--
+-- Name: reverse_textregexeq(text, text); Type: FUNCTION; Schema: public; Owner: -
+--
+
+CREATE FUNCTION public.reverse_textregexeq(text, text) RETURNS boolean
+    LANGUAGE sql IMMUTABLE PARALLEL SAFE
+    AS $_$ SELECT textregexeq($2, $1); $_$;
+
+
 --
 -- Name: testprs_end(internal); Type: FUNCTION; Schema: public; Owner: -
 --
@@ -388,6 +397,17 @@ CREATE FUNCTION public.testprs_start(internal, integer) RETURNS internal
     AS '$libdir/test_parser', 'testprs_start';
 
 
+--
+-- Name: ~<<; Type: OPERATOR; Schema: public; Owner: -
+--
+
+CREATE OPERATOR public.~<< (
+    FUNCTION = public.reverse_textregexeq,
+    LEFTARG = text,
+    RIGHTARG = text
+);
+
+
 --
 -- Name: testparser; Type: TEXT SEARCH PARSER; Schema: public; Owner: -
 --
@@ -7849,6 +7869,7 @@ INSERT INTO "schema_migrations" (version) VALUES
 ('20210106212805'),
 ('20210108030722'),
 ('20210108030723'),
-('20210108030724');
+('20210108030724'),
+('20210110015410');
 
 

test/unit/concerns/searchable.rb

@@ -127,6 +127,9 @@ class SearchableTest < ActiveSupport::TestCase
         assert_search_equals(@wp, other_names_include_any_lower_array: ["A1", "BLAH"])
         assert_search_equals(@wp, other_names_include_all_lower_array: ["A1", "B2"])
 
+        assert_search_equals(@wp, any_other_name_matches_regex: "^a")
+        assert_search_equals(@wp, any_other_name_matches_regex: "[a-z][0-9]")
+
         assert_search_equals(@wp, other_name_count: 2)
       end
     end