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util.datamanager: Add way to efficiently remove first items in a list

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Copying data without parsing it should be more performant than parsing
it serializing back.
This commit is contained in:
Kim Alvefur 2023-07-12 11:42:41 +02:00
parent deecaafbfb
commit 50ae2083ca
1 changed files with 92 additions and 0 deletions
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92
util/datamanager.lua
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@ -506,6 +506,97 @@ local function list_open(username, host, datastore)
return setmetatable({ file = file; index = index }, indexed_list_mt);
end
local function shift_index(index_filename, index, trim_to, offset)
local index_scratch = index_filename .. "~";
local new_index, err = io_open(index_scratch, "w");
if not new_index then
os_remove(index_filename);
return "deleted", err;
end
local ok, err = new_index:write(index_magic);
if not ok then
new_index:close();
os_remove(index_filename);
os_remove(index_scratch);
return "deleted", err;
end
if not index.file or not index.file:seek("set", index_item_size * trim_to) then
new_index:close();
os_remove(index_filename);
os_remove(index_scratch);
return "deleted";
else
local pack, unpack = string.pack, string.unpack;
for item in index.file:lines(index_item_size) do
local ok, err = new_index:write(pack(index_fmt, unpack(index_fmt, item) - offset));
if not ok then
os_remove(index_filename);
os_remove(index_scratch);
return "deleted", err;
end
end
local ok, err = new_index:close();
if not ok then
os_remove(index_filename);
os_remove(index_scratch);
return "deleted", err;
end
return os_rename(index_scratch, index_filename);
end
end
local function list_shift(username, host, datastore, trim_to)
if trim_to == 1 then
return true
end
if type(trim_to) ~= "number" or trim_to < 1 then
return nil, "invalid-argument";
end
local list_filename = getpath(username, host, datastore, "list");
local index_filename = getpath(username, host, datastore, "lidx");
local index, err = get_list_index(username, host, datastore);
if not index then
return nil, err;
end
local new_first = index[trim_to];
if not new_first then
os_remove(index_filename);
return os_remove(list_filename);
end
local offset = new_first.start;
if offset == 0 then
return true;
end
local r, err = io_open(list_filename, "r");
if not r then
return nil, err;
end
local w, err = io_open(list_filename .. "~", "w");
if not w then
return nil, err;
end
r:seek("set", offset);
for block in r:lines(0x1000) do
local ok, err = w:write(block);
if not ok then
return nil, err;
end
end
r:close();
local ok, err = w:close();
if not ok then
return nil, err;
end
shift_index(index_filename, index, trim_to, offset)
return os_rename(list_filename .. "~", list_filename);
end
local type_map = {
keyval = "dat";
list = "list";
@ -609,4 +700,5 @@ return {
build_list_index = build_list_index;
list_open = list_open;
list_shift = list_shift;
};