This is something I have thought a lot recently since I recently saw a project that absolute didn’t care in the slightest about this and used many vendor specific features of MS SQL all over the place which had many advantages in terms of performance optimizations.

Basically everyone always advises you to write your backend so generically with technologies like ODBC, JDBC, Hibernate, … and never use anything vendor specific like stored procedures, vendor specific datatypes or meta queries with the argument being that you can later switch your DBMS without much hassle.

I really wonder if this actually happens in the real world with production Software or if this is just some advice that makes sense on surface level but in reality never pans out. I personally haven’t seen any large piece of Software switch to a different DBMS, even if there would be long term advantages of doing so, because the risk and work to retest everything would be far too great.

The only examples I know of (like SAP) were really part of a much larger rewrite or update rather than “just” switching DBMS.

  • JakenVeina@lemm.eeEnglish
    2·
    9 months ago

    I think it’s a fallacy to say that you can or should build an application layer that’s completely DBMS agnostic. Even if you are very careful to only write SQL queries with features that are part of the official SQL standard, you’re still coupled to your particular DBMS’s internal implementations for query compilation, planning, optimization, etc. At enterprise scale, there’s still going to be plenty of queries that suddenly perform like crap, after a DBMS swap.

    In my mind, standardization for things like ODBC or Hibernate or Entity Framework or whatever else isn’t meant to abstract away the underlying DBMS, it’s meant to promote compatibility.

    Not to mention that you’re tying your own hands by locking yourself out of non-standard DBMS features, that you could be REALLY useful to you, if you have the right use-cases. JSON generation and indexing is the big one that comes to mind. Also, geospatial data tables.

    For context, my professional work for the past 6 years is an Oracle/.NET/Browser application, and we are HEAVILY invested in Oracle. Most notably, we do a LOT of ETL, and that all runs exclusively in the DBMS itself, in PL/SQL procedures orchestratedbbybthe Oracle job scheduler. Attempting to do this kind of data manipulation by round-tripping it into .NET code would make things significantly worse.

    So, my opinion could definitely be a result of what’s been normalized for me, in my day job. But I’ve also had a few other collaborative side projects where I think the “don’t try and abstract away the DBMS” advice holds true.