[GitHub] [couchdb] noahshaw11 commented on a change in pull request #3766: Add smoosh queue persistence

[GitBox <gi...@apache.org>]

noahshaw11 commented on a change in pull request #3766:
URL: https://github.com/apache/couchdb/pull/3766#discussion_r733182102



##########
File path: src/smoosh/src/smoosh_priority_queue.erl
##########
@@ -12,32 +12,70 @@
 
 -module(smoosh_priority_queue).
 
--export([new/0, last_updated/2, is_key/2, in/4, in/5, out/1, size/1, info/1]).
+-export([new/1]).
+
+-export([open/1, last_updated/2, is_key/2, in/4, in/5, out/1, size/1, info/1]).
+
+-export([flush/1]).
+
+-export([from_list/2, to_list/1]).
+
+-export([file_name/1, write_to_file/1]).
+
+-define(VSN, 1).
 
 -record(priority_queue, {
-    dict=dict:new(),
-    tree=gb_trees:empty()
+    name,
+    map,
+    tree
 }).
 
-new() ->
-    #priority_queue{}.
+new(Name) ->
+    #priority_queue{name=Name, map=maps:new(), tree=gb_trees:empty()}.
+
+open(#priority_queue{name=Name} = Q) ->
+    case do_open(file_name(Q)) of
+        {ok, Terms} ->
+            Tree = maps:fold(fun(Key, {TreeKey, Value}, TreeAcc) ->
+                gb_trees:enter(TreeKey, {Key, Value}, TreeAcc)
+            end, gb_trees:empty(), Terms),
+            Q1 = #priority_queue{name=Name, map=Terms, tree=Tree},
+            write_to_file(Q1),

Review comment:
       This is something I would like to discuss. The issue I am thinking about is the bloat of `.queue` files on the file system. [Here](https://github.com/apache/couchdb/pull/3766/files/3aa3b7f743ba8cbf460d431e6f2cfa8a0963b9ed#diff-e1a750216ea14302008b3dfa1bbdec43a968fcb06939d6b91b1404fd37273091R146) I am deleting the file even on successful reads. I could leave the file on a successful read, but if an error is found and returned from `do_open/1` then I would only `write_to_file/1` then. What do you think?




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