Multiple changes.

- Complete first round of documentation.
  - Complete first round of tests and coverage.
  - Expand the thread benchmarker for testing metasync.
  - Add enumerators (each_key/each_value/each_pair) using cursors.
  - Remove keys() implementation in favor of using the emumerable.
  - Make deserialization more DRY.
  - Add an efficient length() method.
  - Add various Hash-alike methods.
  - General code cleanup for release.

FossilOrigin-Name: 0d2bd3995f203c9ac1734ac3da32dd2f09efda9a394e554e6006e44dd07a33b0

experiments/thread_usage.rb

@@ -7,10 +7,6 @@ require 'fileutils'
 
 include FileUtils
 
-
-db = MDBX::Database.open( 'tmpdb' )
-mtx = Mutex.new
-
 at_exit do
 	rm_r 'tmpdb'
 end
@@ -20,31 +16,17 @@ WRITES_PER   = 1000
 
 puts "#{THREAD_COUNT} simultaneous threads, #{WRITES_PER} writes each:"
 
-Benchmark.bm( 10 ) do |x|
-	x.report( " txn per write:" ) do
-		threads = []
-		THREAD_COUNT.times do |i|
-			threads << Thread.new do
-				mtx.synchronize do
-					WRITES_PER.times do
-						key = "%02d-%d" % [ i, rand(1000) ]
-						db[ key ] = rand(1000)
-					end
-				end
-			end
-		end
-		threads.map( &:join )
-	end
+def run_bench( db, msg )
+	mtx = Mutex.new
+	Benchmark.bm( 10 ) do |x|
+		puts msg
+		puts '-' * 60
 
-
-	# Long running transactions require a mutex across threads.
-	#
-	x.report( "txn per thread:" ) do
-		threads = []
-		THREAD_COUNT.times do |i|
-			threads << Thread.new do
-				mtx.synchronize do
-					db.transaction do
+		x.report( " txn per write:" ) do
+			threads = []
+			THREAD_COUNT.times do |i|
+				threads << Thread.new do
+					mtx.synchronize do
 						WRITES_PER.times do
 							key = "%02d-%d" % [ i, rand(1000) ]
 							db[ key ] = rand(1000)
@@ -52,18 +34,48 @@ Benchmark.bm( 10 ) do |x|
 					end
 				end
 			end
+			threads.map( &:join )
 		end
-		threads.map( &:join )
-	end
 
-	x.report( "    unthreaded:" ) do
-		db.transaction do
-			( THREAD_COUNT * WRITES_PER ).times do
-				key = "000-%d" % [ rand(1000) ]
-				db[ key ] = rand(1000)
+
+		# Long running transactions require a mutex across threads.
+		#
+		x.report( "txn per thread:" ) do
+			threads = []
+			THREAD_COUNT.times do |i|
+				threads << Thread.new do
+					mtx.synchronize do
+						db.transaction do
+							WRITES_PER.times do
+								key = "%02d-%d" % [ i, rand(1000) ]
+								db[ key ] = rand(1000)
+							end
+						end
+					end
+				end
+			end
+			threads.map( &:join )
+		end
+
+		x.report( "    unthreaded:" ) do
+			db.transaction do
+				( THREAD_COUNT * WRITES_PER ).times do
+					key = "000-%d" % [ rand(1000) ]
+					db[ key ] = rand(1000)
+				end
 			end
 		end
 	end
+
+	db.close
+	puts
 end
 
 
+db = MDBX::Database.open( 'tmpdb' )
+run_bench( db, "Default database flags:" )
+
+db = MDBX::Database.open( 'tmpdb', no_metasync: true )
+run_bench( db, "Disabled metasync:" )
+
+