prosody
affaf6d08d26
util/datamanager.lua

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Software / code / prosody

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util/datamanager.lua @ 13186:affaf6d08d26

util.datamanager: Pad list writes to avoid crossing block boundaries By padding items so that they do not cross block boundaries, it becomes eaiser to delete whole blocks with fallocate() without cutting items in half, improving efficiency of such operations. Since list stores are used for message archives, where the most common deletion operation would be of the oldest entires, at the top of the file. With this, all blocks that contain items to be removed could be deleted without needing to read, delete and write out the whole file.
author Kim Alvefur <zash@zash.se>
date Wed, 07 Jun 2023 00:39:30 +0200
parent 13185:b57f45165e1e
child 13231:6a11d92ae436
comparison
equal deleted inserted replaced
13185:b57f45165e1e 13186:affaf6d08d26
30 -- Extract directory separator from package.config (an undocumented string that comes with lua) 30 -- Extract directory separator from package.config (an undocumented string that comes with lua)
31 local path_separator = assert ( package.config:match ( "^([^\n]+)" ) , "package.config not in standard form" ) 31 local path_separator = assert ( package.config:match ( "^([^\n]+)" ) , "package.config not in standard form" )
32 32
33 local prosody = prosody; 33 local prosody = prosody;
34 34
35 local blocksize = 0x1000;
35 local raw_mkdir = lfs.mkdir; 36 local raw_mkdir = lfs.mkdir;
36 local atomic_append; 37 local atomic_append;
37 local remove_blocks; 38 local remove_blocks;
38 local ENOENT = 2; 39 local ENOENT = 2;
39 pcall(function() 40 pcall(function()
242 return atomic_store(filename, data); 243 return atomic_store(filename, data);
243 -- File did probably not exist, let's create it 244 -- File did probably not exist, let's create it
244 end 245 end
245 246
246 local pos = f:seek("end"); 247 local pos = f:seek("end");
248 if (blocksize-(pos%blocksize)) < (#data%blocksize) then
249 -- pad to blocksize with newlines so that the next item is both on a new
250 -- block and a new line
251 atomic_append(f, ("\n"):rep(blocksize-(pos%blocksize)));
252 pos = f:seek("end");
253 end
247 254
248 local ok, msg = atomic_append(f, data); 255 local ok, msg = atomic_append(f, data);
249 256
250 if not ok then 257 if not ok then
251 f:close(); 258 f:close();