I realize this is no small feature request so I would like to outline why running MySQL besides for example an existing PostgreSQL installation is no small feat.
For a DB installation you need things like; a high availability setup, monitoring and alerting setup (with useful alerts like replication lag exceeding thresholds, etc), a disaster recovery plan (i.e. backup, preferably a combination of full backups combined with streaming logs to minimize dataloss. You need to encrypt these backups for compliance, ensure you have a plan on how to backup the keys for this encryption, etc.), monitoring of this backup solution, regularly testing this disaster recovery plan and I'm probably leaving out a whole bunch of stuff which you also need.
So speaking from personal experience I have such a setup for PostgreSQL. Configuring and maintaining such a stack for MySQL for just GLPI is just not feasible.
From a technical perspective I would say that both MySQL and PostgreSQL support enough of the more recent ANSI SQL standards that all the required SQL functionality should be there to stay compatible between the 2. I also realize there will also always be some corner cases which require specific queries for MySQL and PostgreSQL. Though I think 99% of the queries could be compatible between the two.
I realize this is no small feature request so I would like to outline why running MySQL besides for example an existing PostgreSQL installation is no small feat.
For a DB installation you need things like; a high availability setup, monitoring and alerting setup (with useful alerts like replication lag exceeding thresholds, etc), a disaster recovery plan (i.e. backup, preferably a combination of full backups combined with streaming logs to minimize dataloss. You need to encrypt these backups for compliance, ensure you have a plan on how to backup the keys for this encryption, etc.), monitoring of this backup solution, regularly testing this disaster recovery plan and I'm probably leaving out a whole bunch of stuff which you also need.
So speaking from personal experience I have such a setup for PostgreSQL. Configuring and maintaining such a stack for MySQL for just GLPI is just not feasible.
From a technical perspective I would say that both MySQL and PostgreSQL support enough of the more recent ANSI SQL standards that all the required SQL functionality should be there to stay compatible between the 2. I also realize there will also always be some corner cases which require specific queries for MySQL and PostgreSQL. Though I think 99% of the queries could be compatible between the two.