From 7320b346815b354fc3f84611995163de463ed1d0 Mon Sep 17 00:00:00 2001 From: martinsumner Date: Wed, 25 Jan 2017 12:38:33 +0000 Subject: [PATCH] Comment update --- src/leveled_sst.erl | 20 ++++++++------------ 1 file changed, 8 insertions(+), 12 deletions(-) diff --git a/src/leveled_sst.erl b/src/leveled_sst.erl index 7978c63..c8600bb 100644 --- a/src/leveled_sst.erl +++ b/src/leveled_sst.erl @@ -8,7 +8,7 @@ %% -------- Slots --------- %% %% The view is built from sublists referred to as slot. Each slot is up to 128 -%% keys and values in size. Three strategis have been benchmarked for the +%% keys and values in size. Three strategies have been benchmarked for the %% slot: a skiplist, a gb-tree, four blocks of flat lists with an index. %% %% Skiplist: @@ -23,7 +23,7 @@ %% %% Indexed Blocks: %% build and serialise slot 342 microseconds -%% de-deriaise and check * 128 - 6746 microseconds +%% de-deserialise and check * 128 - 6746 microseconds %% flatten back to list - 187 microseconds %% %% The negative side of using Indexed Blocks is the storage of the index. In @@ -34,23 +34,19 @@ %% %% -------- Blooms --------- %% -%% There is a summary bloom for the table. the summary bloom is split by the -%% first byte of the hash, and consists of two hashes (derived from the -%% remainder of the hash). This is the top bloom, and the size varies by -%% level. -%% Level 0 has 8 bits per key - 0.05 fpr -%% Level 1 has 6 bits per key - 0.08 fpr -%% Other Levels have 4 bits per key - 0.15 fpr +%% There is a bloom for each slot - based on two hashes and 8 bits per key. %% -%% With the indexed block implementation of the slot a second slot-level bloom -%% is unnecessary (as the index itself yields a 0.003 % fpr). +%% Hashing for blooms is a challenge, as the slot is a slice of an ordered +%% list of keys with a fixed format. It is likely that the keys may vary by +%% only one or two ascii characters, and there is a desire to avoid the +%% overhead of cryptographic hash functions that may be able to handle this. %% %% -------- Summary --------- %% %% Each file has a summary - which is the 128 keys at the top of each slot in %% a skiplist, with some basic metadata about the slot stored as the value. %% -%% The summary is stored seperately to the slots (wihtin the same file). +%% The summary is stored seperately to the slots (within the same file). %% %% -------- CRC Checks --------- %%