Attempt to suppress fork warnings form SQlite3

see: sparklemotion/sqlite3-ruby#558

lib/bob_ross/cache.rb

@@ -23,21 +23,26 @@ def initialize(path, cachefile, size: nil)
         size = (dev_size * (size.to_i / 100.0)).round
       end
       @max_size = size || 1_073_741_824
+    end
+
+    def db
+      return @db if instance_variable_defined?(:@db)
 
       @db = SQLite3::Database.new(cachefile)
       @db.busy_timeout = 300
       migrate
+      @db
     end
 
     def migrate
-      tables = @db.execute(<<-SQL).flatten
+      tables = db.execute(<<-SQL).flatten
         SELECT name FROM sqlite_master
         WHERE type='table'
         ORDER BY name;
       SQL
 
       if !tables.include?('transformations')
-        @db.execute <<-SQL
+        db.execute <<-SQL
           CREATE TABLE transformations (
             hash VARCHAR,
             transparent BOOLEAN,
@@ -50,33 +55,33 @@ def migrate
           );
         SQL
 
-        @db.execute <<-SQL
+        db.execute <<-SQL
           CREATE UNIQUE INDEX thttm ON transformations (hash, transform, transformed_mime);
         SQL
 
-        @db.execute <<-SQL
+        db.execute <<-SQL
           CREATE INDEX tta ON transformations (transformed_at);
         SQL
 
-        @db.execute <<-SQL
+        db.execute <<-SQL
           CREATE TABLE stats (
             key VARCHAR,
             value INTEGER
           );
         SQL
 
-        @db.execute <<-SQL
+        db.execute <<-SQL
           INSERT INTO stats (key, value) VALUES ('size', 0);
         SQL
 
-        @db.execute <<-SQL
+        db.execute <<-SQL
           CREATE TRIGGER stats_trigger_a AFTER INSERT ON transformations
           FOR EACH ROW BEGIN
             UPDATE stats SET value = (value + new.size) WHERE stats.key = 'size';
           END
         SQL
 
-        @db.execute <<-SQL
+        db.execute <<-SQL
           CREATE TRIGGER stats_trigger_b AFTER DELETE ON transformations
           FOR EACH ROW BEGIN
             UPDATE stats SET value = (value - old.size) WHERE stats.key = 'size';
@@ -86,7 +91,7 @@ def migrate
     end
 
     def get(hash, transform)
-      @db.execute(<<-SQL, [hash, transform]).to_a
+      db.execute(<<-SQL, [hash, transform]).to_a
         SELECT hash, transparent, transform, size, transformed_mime, transformed_at FROM transformations
         WHERE hash = ? AND transform = ?
       SQL
@@ -95,7 +100,7 @@ def get(hash, transform)
 
     def use(hash, transform, mime)
       file = File.open(destination(hash, transform, mime))
-      @db.execute(<<-SQL, [Time.now.to_i, hash, transform, mime])
+      db.execute(<<-SQL, [Time.now.to_i, hash, transform, mime])
         UPDATE transformations
         SET last_used_at = ?
         WHERE hash = ? AND transform = ? AND transformed_mime = ?;
@@ -117,7 +122,7 @@ def set(hash, transparent, transform, mime, path)
 
       FileUtils.mkdir_p(File.dirname(dest))
       FileUtils.cp(path, dest)
-      @db.execute(<<-SQL, [hash, transparent ? 1 : 0, transform, stat.size, mime, Time.now.to_i, Time.now.to_i])
+      db.execute(<<-SQL, [hash, transparent ? 1 : 0, transform, stat.size, mime, Time.now.to_i, Time.now.to_i])
         INSERT INTO transformations (hash, transparent, transform, size, transformed_mime, transformed_at, last_used_at)
         VALUES (?, ?, ?, ?, ?, ?, ?)
       SQL
@@ -134,13 +139,13 @@ def set(hash, transparent, transform, mime, path)
     end
 
     def del(hash)
-      entries = @db.execute(<<-SQL, [hash]).to_a
+      entries = db.execute(<<-SQL, [hash]).to_a
         SELECT hash, transform, transformed_mime FROM transformations
         WHERE hash = ?
       SQL
 
       entries.each do |entry|
-        @db.execute(<<-SQL, [entry[0], entry[1], entry[2]])
+        db.execute(<<-SQL, [entry[0], entry[1], entry[2]])
           DELETE FROM transformations
           WHERE hash = ? AND transform = ? AND transformed_mime = ?
         SQL
@@ -149,7 +154,7 @@ def del(hash)
     end
 
     def size
-      @db.execute("SELECT value FROM stats WHERE stats.key = 'size'").first&.first || 0
+      db.execute("SELECT value FROM stats WHERE stats.key = 'size'").first&.first || 0
     end
 
     def purge!(buffer = 0)
@@ -161,11 +166,11 @@ def purge!(buffer = 0)
         purged = 0
         need_to_purge = new_size - @max_size
         while purged < need_to_purge
-          r = @db.execute("SELECT hash, transform, transformed_mime, size FROM transformations ORDER BY last_used_at ASC LIMIT 1").first
+          r = db.execute("SELECT hash, transform, transformed_mime, size FROM transformations ORDER BY last_used_at ASC LIMIT 1").first
           if r.nil?
             return
           else
-            @db.execute(<<-SQL, [r[0], r[1], r[2]])
+            db.execute(<<-SQL, [r[0], r[1], r[2]])
               DELETE FROM transformations
               WHERE hash = ? AND transform = ? AND transformed_mime = ?
             SQL