vim: refactor database handling

To minimize memory usage we need to destroy the queries and the
databases, so we should keep track of them.

Each buffer gets a database connection that is destroyed when the buffer
is destroyed, and all the queries along with it.

Ideally notmuch should destroy the queries when the database is
destroyed, but it's not doing that at the moment.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>

vim/notmuch.vim

@@ -80,6 +80,7 @@ function! s:new_file_buffer(type, fname)
 	exec printf('edit %s', a:fname)
 	execute printf('set filetype=notmuch-%s', a:type)
 	execute printf('set syntax=notmuch-%s', a:type)
+	ruby $curbuf.init(VIM::evaluate('a:type'))
 	ruby $buf_queue.push($curbuf.number)
 endfunction
 
@@ -195,6 +196,7 @@ function! s:search_search_prompt()
 	setlocal modifiable
 ruby << EOF
 	$cur_search = VIM::evaluate('text')
+	$curbuf.reopen
 	search_render($cur_search)
 EOF
 	setlocal nomodifiable
@@ -206,6 +208,7 @@ endfunction
 
 function! s:search_refresh()
 	setlocal modifiable
+	ruby $curbuf.reopen
 	ruby search_render($cur_search)
 	setlocal nomodifiable
 endfunction
@@ -227,6 +230,7 @@ endfunction
 
 function! s:folders_refresh()
 	setlocal modifiable
+	ruby $curbuf.reopen
 	ruby folders_render()
 	setlocal nomodifiable
 endfunction
@@ -254,6 +258,7 @@ function! s:show_next_thread()
 endfunction
 
 function! s:kill_this_buffer()
+	ruby $curbuf.close
 	bdelete!
 ruby << EOF
 	$buf_queue.pop
@@ -276,6 +281,7 @@ function! s:new_buffer(type)
 	keepjumps 0d
 	execute printf('set filetype=notmuch-%s', a:type)
 	execute printf('set syntax=notmuch-%s', a:type)
+	ruby $curbuf.init(VIM::evaluate('a:type'))
 	ruby $buf_queue.push($curbuf.number)
 endfunction
 
@@ -295,8 +301,7 @@ ruby << EOF
 	$cur_thread = thread_id
 	$messages.clear
 	$curbuf.render do |b|
-		do_read do |db|
-			q = db.query(get_cur_view)
+		q = $curbuf.query(get_cur_view)
 		q.sort = 0
 		msgs = q.search_messages
 		msgs.each do |msg|
@@ -322,7 +327,6 @@ ruby << EOF
 		end
 		b.delete(b.count)
 	end
-	end
 	$messages.each_with_index do |msg, i|
 		VIM::command("syntax region nmShowMsg#{i}Desc start='\\%%%il' end='\\%%%il' contains=@nmShowMsgDesc" % [msg.start, msg.start + 1])
 		VIM::command("syntax region nmShowMsg#{i}Head start='\\%%%il' end='\\%%%il' contains=@nmShowMsgHead" % [msg.start + 1, msg.body_start])
@@ -469,24 +473,6 @@ ruby << EOF
 		end
 	end
 
-	def do_write
-		db = Notmuch::Database.new($db_name, :mode => Notmuch::MODE_READ_WRITE)
-		begin
-			yield db
-		ensure
-			db.close
-		end
-	end
-
-	def do_read
-		db = Notmuch::Database.new($db_name)
-		begin
-			yield db
-		ensure
-			db.close
-		end
-	end
-
 	def open_reply(orig)
 		help_lines = [
 			'Notmuch-Help: Type in your message here; to help you use these bindings:',
@@ -559,21 +545,18 @@ ruby << EOF
 			folders = VIM::evaluate('g:notmuch_rb_folders')
 			count_threads = VIM::evaluate('g:notmuch_rb_folders_count_threads')
 			$searches.clear
-			do_read do |db|
 			folders.each do |name, search|
-					q = db.query(search)
+				q = $curbuf.query(search)
 				$searches << search
 				count = count_threads ? q.search_threads.count : q.search_messages.count
 				b << "%9d %-20s (%s)" % [count, name, search]
 			end
 		end
 	end
-	end
 
 	def search_render(search)
 		date_fmt = VIM::evaluate('g:notmuch_rb_date_format')
-		db = Notmuch::Database.new($db_name)
-		q = db.query(search)
+		q = $curbuf.query(search)
 		$threads.clear
 		t = q.search_threads
 
@@ -593,7 +576,7 @@ ruby << EOF
 	end
 
 	def do_tag(filter, tags)
-		do_write do |db|
+		$curbuf.do_write do |db|
 			q = db.query(filter)
 			q.search_messages.each do |e|
 				e.freeze
@@ -610,6 +593,40 @@ ruby << EOF
 				e.thaw
 				e.tags_to_maildir_flags
 			end
+			q.destroy!
+		end
+	end
+
+	module DbHelper
+		def init(name)
+			@name = name
+			@db = Notmuch::Database.new($db_name)
+			@queries = []
+		end
+
+		def query(*args)
+			q = @db.query(*args)
+			@queries << q
+			q
+		end
+
+		def close
+			@queries.delete_if { |q| ! q.destroy! }
+			@db.close
+		end
+
+		def reopen
+			close if @db
+			@db = Notmuch::Database.new($db_name)
+		end
+
+		def do_write
+			db = Notmuch::Database.new($db_name, :mode => Notmuch::MODE_READ_WRITE)
+			begin
+				yield db
+			ensure
+				db.close
+			end
 		end
 	end
 
@@ -658,6 +675,8 @@ ruby << EOF
 	end
 
 	class VIM::Buffer
+		include DbHelper
+
 		def <<(a)
 			append(count(), a)
 		end