Allow clear with delete or truncate

Defaults to `truncate`, but can be set with the `clear_with` option.

If `Rails.test.env?` is true though it will default to `delete` as
truncation is not always transactional (e.g. in MySQL) so clearing the
cache would break transactional tests.

README.md

@@ -80,9 +80,10 @@ Solid cache supports these options in addition to the universal `ActiveSupport::
 - `trim_batch_size` - the batch size to use when deleting old records (default: `100`)
 - `max_age` - the maximum age of entries in the cache (default: `2.weeks.to_i`)
 - `max_entries` - the maximum number of entries allowed in the cache (default: `2.weeks.to_i`)
-- `cluster` - a Hash of options for the cache database cluster, e.g `{ shards: [:database1, :database2, :database3] }``
+- `cluster` - a Hash of options for the cache database cluster, e.g `{ shards: [:database1, :database2, :database3] }`
 - `clusters` - and Array of Hashes for multiple cache clusters (ignored if `:cluster` is set)
 - `active_record_instrumentation` - whether to instrument the cache's queries (default: `true`)
+- `clear_with` - clear the cache with `:truncate` or `:delete` (default `truncate`, except for when Rails.env.test? then `delete`)
 
 For more information on cache clusters see [Sharding the cache](#sharding-the-cache)
 ### Cache trimming

app/models/solid_cache/entry.rb

@@ -36,10 +36,14 @@ def delete_matched(matcher, batch_size:)
  end
  end
 
- def clear
+ def clear_truncate
  connection.truncate(table_name)
  end
 
+ def clear_delete
+ in_batches.delete_all
+ end
+
  def increment(key, amount)
  transaction do
  uncached do

lib/solid_cache/store/entries.rb

@@ -1,6 +1,19 @@
 module SolidCache
  class Store
  module Entries
+ attr_reader :clear_with
+
+ def initialize(options = {})
+ super(options)
+
+ # Truncating in test mode breaks transactional tests in MySQL (not in Postgres though)
+ @clear_with = options.fetch(:clear_with) { Rails.env.test? ? :delete : :truncate }&.to_sym
+
+ unless [:truncate, :delete].include?(clear_with)
+ raise ArgumentError, "`clear_with` must be either ``:truncate`` or ``:delete`"
+ end
+ end
+
  private
  def entry_delete_matched(matcher, batch_size)
  writing_all(failsafe: :delete_matched) do
@@ -10,7 +23,11 @@ def entry_delete_matched(matcher, batch_size)
 
  def entry_clear
  writing_all(failsafe: :clear) do
- Entry.clear
+ if clear_with == :truncate
+ Entry.clear_truncate
+ else
+ Entry.clear_delete
+ end
  end
  end
 

test/models/solid_cache/entry_test.rb

@@ -20,5 +20,24 @@ class EntryTest < ActiveSupport::TestCase
 
  assert_equal 2, Entry.uncached { Entry.id_range }
  end
+
+ test "clear with truncate" do
+ write_entries
+ assert_equal 20, uncached_entry_count
+ Entry.clear_truncate
+ assert_equal 0, uncached_entry_count
+ end
+
+ test "clear with delete" do
+ write_entries
+ assert_equal 20, uncached_entry_count
+ Entry.clear_delete
+ assert_equal 0, uncached_entry_count
+ end
+
+ private
+ def write_entries(count = 20)
+ Entry.write_multi(count.times.map { |i| { key: "key#{i}", value: "value#{i}" } })
+ end
  end
 end

test/test_helper.rb

@@ -40,3 +40,7 @@ def send_entries_back_in_time(distance)
  end
  end
 end
+
+def uncached_entry_count
+ SolidCache.each_shard.sum { SolidCache::Entry.uncached { SolidCache::Entry.count } }
+end

test/unit/clear_test.rb

@@ -0,0 +1,34 @@
+require "test_helper"
+
+class DeleteMatchedTest < ActiveSupport::TestCase
+ setup do
+ @namespace = "test-#{SecureRandom.hex}"
+
+ @delete_cache = lookup_store(expires_in: 60, clear_with: :delete)
+ end
+
+ test "clear by truncation" do
+ cache = lookup_store(expires_in: 60, clear_with: :truncate)
+ write_values(cache)
+
+ cache.clear
+
+ assert_equal cache.clear_with, :truncate
+ assert_equal 0, uncached_entry_count
+ end
+
+ test "clear by deletion" do
+ cache = lookup_store(expires_in: 60, clear_with: :delete)
+ write_values(cache)
+
+ cache.clear
+
+ assert_equal cache.clear_with, :delete
+ assert_equal 0, uncached_entry_count
+ end
+
+ private
+ def write_values(cache)
+ 20.times.map { |i| cache.write("key#{i}", "value#{i}") }
+ end
+end