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| -rw-r--r-- | src/dtree.erl | 22 |
1 files changed, 15 insertions, 7 deletions
diff --git a/src/dtree.erl b/src/dtree.erl index f5c260ef..265bb340 100644 --- a/src/dtree.erl +++ b/src/dtree.erl @@ -14,13 +14,21 @@ %% Copyright (c) 2007-2012 VMware, Inc. All rights reserved. %% -%% A dual-index tree. Entries have a primary key and a set of -%% secondary keys. Most operations require the supply of just the -%% secondary key. Entries exists while they have a non-empty secondar -%% key set. The 'take' operations return the entries that got removed, -%% i.e. that had no remaining secondary keys. take/3 expects entries -%% to exist with the supplied primary keys and secondary key. take/2 -%% can cope with the supplied secondary key having no entries. +%% A dual-index tree. +%% +%% Conceptually, what we want is a map that has two distinct sets of +%% keys (referred to here as primary and secondary, although that +%% shouldn't imply a hierarchy) pointing to one set of +%% values. However, in practice what we'll always want to do is insert +%% a value that's pointed at by (one primary, many secondaries) and +%% remove values that are pointed at by (one secondary, many +%% primaries) or (one secondary, all primaries). Thus the API. +%% +%% Entries exists while they have a non-empty secondary key set. The +%% 'take' operations return the entries that got removed, i.e. that +%% had no remaining secondary keys. take/3 expects entries to exist +%% with the supplied primary keys and secondary key. take/2 can cope +%% with the supplied secondary key having no entries. -module(dtree). |