Fix incorrect caching of case-insensitivity

`false` values would not cache with `||=`, and `begin` would run each time.

Author: pirj

activerecord/CHANGELOG.md

@@ -1,3 +1,10 @@
+*   Fix redundant updates to the column insensitivity cache
+
+    Fixed redundant queries checking column capability for insensitive
+    comparison.
+
+    *Phil Pirozhkov*
+
 *   Allow disabling methods generated by `ActiveRecord.enum`.
 
     *Alfred Dominic*

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -1032,22 +1032,24 @@ def build_statement_pool
 
         def can_perform_case_insensitive_comparison_for?(column)
           @case_insensitive_cache ||= {}
-          @case_insensitive_cache[column.sql_type] ||= begin
-            sql = <<~SQL
-              SELECT exists(
-                SELECT * FROM pg_proc
-                WHERE proname = 'lower'
-                  AND proargtypes = ARRAY[#{quote column.sql_type}::regtype]::oidvector
-              ) OR exists(
-                SELECT * FROM pg_proc
-                INNER JOIN pg_cast
-                  ON ARRAY[casttarget]::oidvector = proargtypes
-                WHERE proname = 'lower'
-                  AND castsource = #{quote column.sql_type}::regtype
-              )
-            SQL
-            execute_and_clear(sql, "SCHEMA", [], allow_retry: true, uses_transaction: false) do |result|
-              result.getvalue(0, 0)
+          @case_insensitive_cache.fetch(column.sql_type) do
+            @case_insensitive_cache[column.sql_type] = begin
+              sql = <<~SQL
+                SELECT exists(
+                  SELECT * FROM pg_proc
+                  WHERE proname = 'lower'
+                    AND proargtypes = ARRAY[#{quote column.sql_type}::regtype]::oidvector
+                ) OR exists(
+                  SELECT * FROM pg_proc
+                  INNER JOIN pg_cast
+                    ON ARRAY[casttarget]::oidvector = proargtypes
+                  WHERE proname = 'lower'
+                    AND castsource = #{quote column.sql_type}::regtype
+                )
+              SQL
+              execute_and_clear(sql, "SCHEMA", [], allow_retry: true, uses_transaction: false) do |result|
+                result.getvalue(0, 0)
+              end
             end
           end
         end

activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb

@@ -455,6 +455,21 @@ def test_unparsed_defaults_are_at_least_set_when_saving
         end
       end
 
+      def test_only_check_for_insensitive_comparison_capability_once
+        with_example_table "id SERIAL PRIMARY KEY, number INTEGER" do
+          number_klass = Class.new(ActiveRecord::Base) do
+            self.table_name = "ex"
+          end
+          attribute = number_klass.arel_table[:number]
+          assert_queries :any, ignore_none: true do
+            @connection.case_insensitive_comparison(attribute, "foo")
+          end
+          assert_no_queries do
+            @connection.case_insensitive_comparison(attribute, "foo")
+          end
+        end
+      end
+
       private
         def with_example_table(definition = "id serial primary key, number integer, data character varying(255)", &block)
           super(@connection, "ex", definition, &block)