Add a little script to show comme use of the databases.

spec/test-common.cr

@@ -120,4 +120,69 @@ describe "SPECDB::Common" do
 		index4_color.data.size.should eq 1 # trigger cache: 1, the color "red"
 		index4_color.data["red"].size.should eq 3 # 3 values in "red"
 	end
+
+	it "testing caches: add some values, clear cache, check the values" do
+		car0 = Car.new "Corvet-0", "red",    [] of String
+		car1 = Car.new "Corvet-1", "red",    [] of String
+		car2 = Car.new "Corvet-2", "blue",   [] of String
+		car3 = Car.new "Corvet-3", "violet", [] of String
+
+		db = SPECDB::Common(Car).new "reindex", 2
+		index_name  = db.new_index     "name",  &.name
+		index_color = db.new_partition "color", &.color
+
+		db << car0
+
+		# First entry, each cache should have one item.
+		index_name.data.size.should  eq 1
+		index_color.data.size.should eq 1
+
+		db << car1
+		db << car2
+		db << car3
+
+		# Storage cache should only have the maximum number of allowed entries (2).
+		db.data.keys.size.should eq 2
+
+		# Trigger caches don't have limits on the number of entries, therefore they should have:
+		# 4 entries for the name index (each entry = 1 car).
+		index_name.data.size.should  eq 4
+		# 3 entries for the color index (each entry = 1 color).
+		index_color.data.size.should eq 3
+
+		# All cached entries are dropped.
+		db.clear_cache!
+
+		# Caches should be empty.
+		db.data.keys.sort.should eq([] of Int32)
+		index_name.data.size.should  eq 0
+		index_color.data.size.should eq 0
+
+		# Get a car from stored data based on its name.
+		index_name.get?("Corvet-2").should eq car2
+		index_name.data.size.should  eq 1
+		# This doesn't fill up the cache in the color index.
+		index_color.data.size.should eq 0
+
+		# Get a car from stored data based on its color.
+		index_color.get?("violet").size.should eq 1
+
+		# The "Storage" database should have both found items in cache.
+		db.data.keys.sort.should eq([2, 3] of Int32)
+
+		# Trigger caches should have a single value given that we searched a single item through each one.
+		index_name.data.size.should  eq 1
+		index_color.data.size.should eq 1
+
+		# Loop over entries, filling up the cache for Storage.
+		total_values = 0
+		db.each_with_key do |v, k|
+			total_values += 1
+		end
+		total_values.should eq 4
+
+		# Caches should still have a single entry since we only searched through them only once.
+		index_name.data.size.should  eq 1
+		index_color.data.size.should eq 1
+	end
 end

spec/various-common-usages.cr

@@ -0,0 +1,79 @@
+require "./db-cars.cr"
+
+rootdb = "/tmp/test-db"
+
+db = DODB::Storage::Cached(Car).new rootdb
+#db = DODB::Storage::Common(Car).new rootdb, 2
+index_name     = db.new_index     "name",     &.name
+index_color    = db.new_partition "color",    &.color
+index_keywords = db.new_tags      "keywords", &.keywords
+
+car0 = Car.new "Corvet-0", "red",    ["shiny"]
+car1 = Car.new "Corvet-1", "red",    ["slow", "expensive"]
+car2 = Car.new "Corvet-2", "blue",   ["fast", "elegant"]
+car3 = Car.new "Corvet-3", "violet", ["expensive"]
+
+db << car0
+db << car1
+db << car2
+db << car3
+
+# Get a car from stored data based on its name.
+if (c = index_name.get?("Corvet-2")) == car2
+	puts "We found the Corvet-2: #{c}"
+else
+	puts "We didn't find the Corvet-2!!!"
+end
+
+# Get a car from stored data based on a keyword.
+if c = index_keywords.get?("elegant")
+	puts "We found the elegant car: #{c}"
+else
+	puts "We didn't find the elegant car!!!"
+end
+
+# All cached entries are dropped.
+# WARNING: the Storage::Cached database don't read anything on the filesystem and relies entirely
+#          on cached values. Therefore, clearing the caches means the database won't answer any request
+#          with the proper values. The content has to be read again through a reindex_everything! for example.
+#db.clear_cache!
+
+db = DODB::Storage::Cached(Car).new rootdb
+index_name     = db.new_index     "name",     &.name
+index_color    = db.new_partition "color",    &.color
+index_keywords = db.new_tags      "keywords", &.keywords
+db.reindex_everything!
+
+# Get a car from stored data based on its color.
+if index_color.get?("violet").size == 1
+	puts "We found the violet car"
+else
+	puts "We didn't find the violet car!!!"
+end
+
+# Get a car from stored data based on a keyword.
+list_of_cars = index_keywords.get?("expensive")
+if ! list_of_cars.nil? && list_of_cars.size > 0
+	puts "We found the expensive cars:"
+	list_of_cars.each { |car| puts "- #{car}" }
+else
+	puts "We didn't find the expensive car!!!"
+end
+
+# Loop over entries, filling up the cache for Storage.
+total_values = 0
+	db.each_with_key do |v, k|
+	total_values += 1
+end
+
+if total_values == 4
+	puts "We found all the values"
+else
+	puts "We didn't find all the values!!!"
+end
+
+FileUtils.rm_r rootdb
+
+# Caches should still have a single entry since we only searched through them only once.
+#index_name.data.size.should  eq 1
+#index_color.data.size.should eq 1

src/dodb/storage.cr

@@ -350,9 +350,23 @@ abstract class DODB::Storage(V)
 		end
 	end
 
+	def clear_storage_cache!
+		# There's no cache by default.
+		# This function has to be changed in storage implementations.
+	end
+
+	# NOTE: clears all caches (`storage` and `triggers`).
+	def clear_cache!
+		clear_storage_cache!
+		@triggers.each do |trigger|
+			trigger.clear_cache!
+		end
+	end
+
 	# Removes all indices and then rewrites them all.
 	#
 	# WARNING: slow operation.
+	# NOTE: clears all caches (`storage` and `triggers`).
 	def reindex_everything!
 		nuke_triggers!
 

src/dodb/storage/cached.cr

@@ -45,13 +45,33 @@ class DODB::Storage::Cached(V) < DODB::Storage(V)
 
 		@cached_last_key = init_last_key
 
+		# Load the database (to fill up the cache) at start-up.
+		load_db!
+	end
+
+	# `Storage::Cached` doesn't perform look-ups from the filesystem by itself upon requests,
+	# the entire database has to be initialized by reading the entire on-disk data in order to
+	# fill up the cache.
+	#
+	# This function is called once at start-up and should be used whenever the entire cache
+	# is cleaned up for whatever reason, otherwise the database will be seen as empty.
+	#
+	# WARNING: beware of triggers.
+	# NOTE: this function has no use in `Storage::Common` because the database entries are read from the disk
+	#	when the value isn't in cache.
+	#       This function doesn't exist in `Storage::Uncached` since there is no cache.
+	def load_db!
 		# Load the database in RAM at start-up.
 		DODB::Storage::Uncached(V).new(@directory_name).each_with_key do |v, key|
-			puts "\rloading data from #{@directory_name} at key #{key}"
+			# puts "\rloading data from #{@directory_name} at key #{key}"
 			self[key] = v
 		end
 	end
 
+	def clear_storage_cache!
+		data.clear
+	end
+
 	# Gets the data with the *key*.
 	# In case the data is missing, returns an exception `DODB::MissingEntry`.
 	#

src/dodb/storage/common.cr

@@ -46,6 +46,17 @@ class DODB::Storage::Common(V) < DODB::Storage::Cached(V)
 		@cached_last_key = init_last_key
 	end
 
+	def clear_storage_cache!
+		data.clear
+		@lru = EfficientLRU(Int32).new lru.max_entries
+	end
+
+	# :nodoc:
+	# There is no need for this function in `Storage::Common`,
+	# therefore it is put in private and removed from the documentation.
+	private def load_db!
+	end
+
 	# Verifies that the value is in cache, or read it on disk.
 	# Pushes the key in the lru.
 	def [](key : Int32) : V

src/dodb/trigger.cr

@@ -29,9 +29,15 @@ abstract class DODB::Trigger(V)
 	# NOTE: used for internal operations.
 	abstract def trigger_directory : String
 
+	# Removes all cached values.
+	def clear_cache!
+		# By default, there is no cache.
+	end
+
 	# Removes all the index entries, removes the `#trigger_directory` by default.
 	#
 	# NOTE: used for internal operations.
+	# NOTE: automatically clears cache (for triggers that do have a cache).
 	def nuke_trigger
 		FileUtils.rm_rf trigger_directory
 	end

src/dodb/trigger/index.cr

@@ -344,10 +344,14 @@ class DODB::Trigger::IndexCached(V) < DODB::Trigger::Index(V)
 		end
 	end
 
+	def clear_cache!
+		data.clear
+	end
+
 	# Clears the cache and removes the `#trigger_directory`.
 	def nuke_trigger
 		super
-		data.clear
+		clear_cache!
 	end
 
 	# Indexes the value on the file-system as `DODB::Trigger::Index#index` but also puts the index in a cache.
@@ -436,6 +440,6 @@ class DODB::Trigger::IndexRAMOnly(V) < DODB::Trigger::IndexCached(V)
 
 	# Clears the index.
 	def nuke_trigger
-		data.clear
+		clear_cache!
 	end
 end

src/dodb/trigger/partition.cr

@@ -260,6 +260,10 @@ class DODB::Trigger::PartitionCached(V) < DODB::Trigger::Partition(V)
 		@data[partition] = array
 	end
 
+	def clear_cache!
+		data.clear
+	end
+
 	# Removes the index of a value on the file-system as `DODB::Trigger::Partition#deindex` but also from
 	# the cache, used for **internal operations**.
 	#
@@ -309,7 +313,7 @@ class DODB::Trigger::PartitionCached(V) < DODB::Trigger::Partition(V)
 	# Clears the cache and removes the `#trigger_directory`.
 	def nuke_trigger
 		super
-		data.clear
+		clear_cache!
 	end
 end
 
@@ -379,6 +383,6 @@ class DODB::Trigger::PartitionRAMOnly(V) < DODB::Trigger::PartitionCached(V)
 
 	# Clears the cache.
 	def nuke_trigger
-		data.clear
+		clear_cache!
 	end
 end

src/dodb/trigger/tags.cr

@@ -300,6 +300,10 @@ class DODB::Trigger::TagsCached(V) < DODB::Trigger::Tags(V)
 		end
 	end
 
+	def clear_cache!
+		data.clear
+	end
+
 	# :inherit:
 	# TODO: in case the tag is left empty, should it be removed from the cache?
 	def deindex(key : String, value : V)
@@ -347,7 +351,7 @@ class DODB::Trigger::TagsCached(V) < DODB::Trigger::Tags(V)
 	# Clears the cache and removes the `#trigger_directory`.
 	def nuke_trigger
 		super
-		data.clear
+		clear_cache!
 	end
 end
 
@@ -421,6 +425,6 @@ class DODB::Trigger::TagsRAMOnly(V) < DODB::Trigger::TagsCached(V)
 
 	# Clears the cache.
 	def nuke_trigger
-		data.clear
+		clear_cache!
 	end
 end

src/lru.cr

@@ -88,6 +88,9 @@ class EfficientLRU(V)
 	property list : DoubleLinkedList(V)
 	property hash : Hash(V, DoubleLinkedList::Node(V))
 
+	# Maximum allowed entries in the structure.
+	property max_entries : UInt32
+
 	def initialize(@max_entries : UInt32)
 		@list = DoubleLinkedList(V).new
 		@hash = Hash(V, DoubleLinkedList::Node(V)).new