Index-based NDN Repository

Junxiao Shi, 2014-06-17

Overall Structure

• Storage: read-write storage for id=>Data packet• Index: sorted associative container for Name=>entry• Query algorithm

Storage API

• typedef <implementation-defined> Id;• Id put(const Data& data);• Data get(Id id);• forward iterator for (Id, Data) – minimal

orforward iterator for (Id, fullName, KeyLocatorHash) – preferred• fullName: full Name including implicit digest• KeyLocatorHash: SHA256 hash of KeyLocator

Storage in SQL Database: Table Structurecolumn type descriptionid INT

AUTO_INCREMENT

name VARBINARY full Name including implicit digest

keylocatorhash BINARY(32) SHA256 hash of KeyLocatordata BLOB the Data packet

• Indexes• PRIMARY KEY id

Index API

• sorted container• entry type: (Id, fullName, KeyLocatorHash)• order by fullName

• bidirectional iterator• lower_bound algorithm

Query Algorithm – Helper Routines

• Query type• interest• KeyLocatorHash: SHA256 hash of PublisherPublicKeyLocator selector, or null• minComponents• maxComponents

• bool matchesSimpleSelectors(Query, Index::iterator)• determines whether the Data described by the index entry can satisfy

MinSuffixComponent, MaxSuffixComponent, PublisherPublicKeyLocator, Exclude

Query Algorithm – leftmost

for (it = index.lower_bound(interest.getName()); it != index.end(); ++it) { if (!interest.getName().isPrefixOf(it->fullName)) return index.end(); if (matchesSimpleSelector(interest, it)) return it;}

Query Algorithm – rightmostboundary = index.lower_bound(interest.getName());if (boundary == index.end() || !interest.getName().isPrefixOf(boundary->fullName)) return index.end();last = index.lower_bound(interest.getName().succ());while (true) { prev = last; --prev; if (prev == boundary) return matchesSimpleSelectors(interest, prev) ? prev : index.end(); first = index.lower_bound(prev->fullName.getPrefix(interest.getName().size() + 1); match = std::find_if(first, last, matchesSimpleSelectors); if (match != last) return match; last = first;}

Query Example – rightmost, non-exact• Dataset: /A/B/d001, /A/C/D/E/d002, /A/C/F/d003, /A/C/G/d004,

/A/C/H/I/d005• Interest /A rightmost MaxSuffixComponents=31. boundary=/A/B/d001, last=end (one past last entry)2. iteration 1: first=/A/C/H/I/d005, last=end, no match3. iteration 2: first=/A/C/D/E/d002, last=/A/C/H/I/d005,

match=/A/C/F/d003

Query Example – rightmost, exact

• Dataset: /A/d000, /A/d000/d001, /A/d002• Interest /A/d000 rightmost MaxSuffixComponents=01. boundary=/A/d000, last=/A/d0022. iteration 1: first=/A/d000/d001, last=/A/d002, no match3. iteration 2: prev=/A/d000, equals boundary,

matchesSimpleSelectors is true, returns /A/d000

Query Algorithm – rightmost, alternate1. start with index.lower_bound(interest.getName().succ())2. iterate to the left, until a match is found3. continue to the left, until fullName.at(interest.getName().size())

changes; return the last match• This algorithm is less efficient when• The dataset is a versioned file, where each version has many segments• The Interest wants to fetch the first segment of the last version• This algorithm must iterate over every segment of the last version

• This algorithm is more efficient for finding the last segment in a sequence, because it calls index.lower_bound() only once