DB matching installation

You can use the VLMAtch function to perform descriptors matching using PostgreSQL database.

To enable matching in db, one needs to:

#) Compile a library with a VLMatch function using appropriate database development libraries. The library is compiled according to the current database version.

1. Import the library in the running database and check it availability.

#) Enable USE_DB_MATCH_FUNCTION parameter in the service settings (/var/lib/luna/current/luna-events/luna_events/config/config.py).

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Instruction for PostgreSQL database

You can find all the required files for the VLMatch user-defined extension (UDx) compilation in the following directory:

/var/lib/luna/current/luna-events/base_scripts/database_matching/postgres

The following instruction describes installation for PostgreSQL 12.

For VLMatch UDx function compilation one needs to:

1. Make sure, that PostgreSQL of the required version is installed and launched.

Install the required PostgreSQL development environment. You can find more information at postgres installation manual.

The llvm-toolset-7-clang is required for postgresql12-devel. Install it from the centos-release-scl-rh repository.

   yum -y install centos-release-scl-rh

   yum -y --enablerepo=centos-sclo-rh-testing install llvm-toolset-7-clang

Then install the development environment.

   sudo yum -y install postgresql12 postgresql12-server postgresql12-devel

2. Install the gcc-c++ package. The package version 4.8 or higher is required.

   yum -y install gcc-c++.x86_64
   

3. Install CMAKE. The version 3.5 or higher is required.

4. Open the make.sh script using a text editor. It includes paths to the currently used PostgreSQL version. Change the following values (if necessary):

   • SDK_HOME specifies the path to PostgreSQL home directory. The default value is /usr/pgsql-12/include/server;

   • LIB_ROOT specifies the path to PostgreSQL library root directory. The default value is /usr/pgsql-12/lib.

Go to the make.sh script directory and run it:

   cd /var/lib/luna/current/luna-events/base_scripts/database_matching/postgres/

   chmod +x make.sh

   ./make.sh

5. Define the function inside the service database:

   sudo -u postgres -h 127.0.0.1 -- psql -d luna_events -c "CREATE FUNCTION VLMatch(bytea, bytea, int) RETURNS float8 AS 'VLMatchSource.so', 'VLMatch' LANGUAGE C PARALLEL SAFE;"
   

6. Test function by sending re following request to the service database:

   sudo -u postgres -h 127.0.0.1 -- psql -d luna_events -c "SELECT VLMatch('\x1234567890123456789012345678901234567890123456789012345678901234'::bytea, '\x0123456789012345678901234567890123456789012345678901234567890123'::bytea, 32);"
   

   The result returned by the database must be “0.4765625”.

7. Check that the USE_DB_MATCH_FUNCTION parameter is enabled in the service settings (/var/lib/luna/current/luna-events/luna_events/config/config.py).