Repository for the source code of the engine presented in the paper The Ring: Worst-case Optimal Joins in Graph Databases using (Almost) No Extra Space

Note: A more recent version is available at this repository. The details of that version are explained in New Compressed Indices for Multijoins on Graph Databases.

To run our code, we have to install an extended version of the library SDSL. Go to this repository and follow the instructions.

After the extended version of SDSL is installed, we have to clone this repository and follow these steps:

1. Create our build folder and compile the code:

mkdir build
cd build
cmake ..
make

Check that there is no errors.

2. Download the version of Wikidata that you want to use:

• Wikidata Filtered (about 80M triples).
• Wikidata (about 1000M triples).

Now put the .dat file inside a folder.

3. Building the index. After compiling the code we should have an executable called build-index in build. Now run:

./build-index <absolute-path-to-the-.dat-file> <type-ring>

<type-ring> can take two values: ring or c-ring. Both are implementations of our ring index but using plain and compressed bitvectors, respectively. This will generate the index in the folder where the .dat file is located. The index is suffixed with .ring or .c-ring according to the second argument.

4. Querying the index. In build folder, you should find another executable file called query-index. To solve the queries you should run:

./query-index <absoulute-path-to-the-index-file> <absolute-path-to-the-query-file>

Note that the second argument is the path to a file that contains all the queries. The queries of our benchmark are in Queries:

• The file Queries-wikidata-benchmark.txt can be run with wikidata-filtered-enumerated.dat.
• The file Queries-bgps-limit1000.txt contains the queries of wikidata-enumerated.dat.

After running that command, you should see the number of the query, the number of results, and the elapsed time of each one of the queries with the following format:

<query number>;<number of results>;<elapsed time>

At the moment, we can find the rest of the complementary material at this webpage. Note that we will find instructions to run the code there, and although the instructions are different from the ones in this repository, they should work too.