ProvSQL

The goal of the ProvSQL project is to add support for (m-)semiring provenance and uncertainty management to PostgreSQL databases, in the form of a PostgreSQL extension/module/plugin. It is work in progress at the moment.

Features

The ProvSQL system currently supports proper management of provenance attached to SQL queries, in the form of a provenance circuit, suitable both for regular Boolean provenance, arbitrary semiring provenance, with or without monus (m-semiring), in the free m-semiring, or specialized to any m-semiring of choice. It also supports where-provenance and probability computation from the provenance, through a variety of methods.

The following SQL queries are currently supported.

Regular SELECT-FROM-WHERE queries (aka conjunctive queries with multiset semantics)
JOIN queries (regular joins only; outer, semijoins, and antijoins are not currently supported)
SELECT queries with nested SELECT subqueries in the FROM clause
GROUP BY queries (without aggregation)
SELECT DISTINCT queries (i.e., set semantics)
UNION's or UNION ALL's of SELECT queries
EXCEPT of SELECT queries

Docker container

As an alternative to a ProvSQL installation (see below), you can try a demonstration version of ProvSQL (full-featured, except for circuit visualization) as a Docker container. To deploy it, once Docker CE is installed, simply run:

docker run inriavalda/provsqldemo

By following the instructions, you will be able to connect to the PostgreSQL server within the container using a PostgreSQL client, and to use a Web interface for simple visualization of where-provenance.

Prerequisites for installation

An install of PostgreSQL >= 9.5. The extension has currently been tested with versions from 9.5 to 11.1 (inclusive) of PostgreSQL, under Linux and Mac OS X (if the extension does not work on a specific version or operating system, a bug report is appreciated).
A compilation environment for PostgreSQL, including the make tool, a C compiler (both can be obtained on Debian-based Linux distributions from the virtual build-essential package), and the headers for your PostgreSQL version (as can be obtained for instance from the postgresql-server-dev-xx package on Debian-based systems, or from the postgresql package on the Homebrew package manager for Mac OS X).
Finally, the uuid-ossp extension for PostgreSQL (on Debian-based systems, it is found in the postgresql-contrib-9.x package for PostgreSQL version 9.x, and is installed automatically for PostgreSQL version >= 10; on Homebrew, in the ossp-uuid package).
Optionally, for probability computation through knowledge compilation, any or all of the following software:
- c2d, from http://reasoning.cs.ucla.edu/c2d/download.php
- d4, from http://www.cril.univ-artois.fr/KC/d4.html
- dsharp, from https://bitbucket.org/haz/dsharp
To be used, an executable with the name of this software must be available in the PATH of the PostgreSQL server user (e.g., in /usr/local/bin/).
Optionally, for circuit visualization, the following software:
- graphviz, for production of PDF circuits (dot executable)
- evince, for visualization of PDF files
Both can be obtained as packages in common Linux distributions.

Installation

Compile the code with make. If you have several installed versions of PostgreSQL, you can change the version the module is compiled against by changing the reference to pg_config in the Makefile.
Install it in the PostgreSQL extensions directory with make install (run as a user with rights to write to the PostgreSQL installation directories).
Add the line
```
shared_preload_libraries = 'provsql'
```
to the postgresql.conf configuration file (on Linux systems, it should be in /etc/postgresql/VERSION/main/postgresql.conf) and restart the PostgreSQL server (e.g., with service postgresql restart on systemd-based distributions). This is required because the extension includes hooks.

Testing your installation

You can test your installation by running make installcheck as a PostgreSQL administrator user. If you do not want to run this as the default administrator user, you can make yourself a PostgreSQL administrator with ALTER USER your_login WITH SUPERUSER. This assumes that your_login is a PostgreSQL user: on Debian-based Linux distributions, you can ensure this by running the command createuser your_login as the postgres user.

Note that the tests that depend on external software (c2d, d4, dsharp, dot) will fail if no executable of that name can be found.

For circuit visualization, the database server will attempt to launch evince on a local X window server (:0). You can authorize the display of such windows with xhost +.

Using ProvSQL

You can use ProvSQL in any PostgreSQL database by loading the provsql extension. See the file setup.sql for an example on how to do this.

You then need to add provenance to an existing table using the provsql.add_provenance(regclass) user-defined function. See add_provenance.sql for an example. The table will have an extra provsql column added. This column is handled in a special way and always represents, in query results, the provenance of each tuple as a UUID.

You can then use this provenance to run computation in various semirings. See security.sql and formula.sql for two examples.

See the other examples in test/sql for other use cases.

A demonstration of the ProvSQL system is available as a video, on https://youtu.be/iqzSNfGHbEE?vq=hd1080 The SQL commands used in this demonstration can be found in the doc/demo/ directory. An article describing this demonstration, presented at the VLDB 2018. conference, is available at http://pierre.senellart.com/publications/senellart2018provsql.pdf

Finally, a ProvSQL tutorial is provided, in the form of a crime mystery. It can be found in the doc/tutorial/ directory.

Uninstalling

You can uninstall ProvSQL by running make uninstall (run as a user with rights to write to the PostgreSQL installation directories), and by removing the reference to provsql in the postgresql.conf configuration file.

License

ProvSQL is provided as open-source software under the MIT License. See LICENSE.

Contact

https://github.com/PierreSenellart/provsql

Pierre Senellart pierre@senellart.com

Bug reports and feature requests are preferably sent through the Issues feature of GitHub.

graydon/provsql