tds_fdw : Severe performance degradation from postgresql 10.23 to 16.4

Achilleas Mantzios <a.mantzios@xxxxxxxxxxxxxxxxxxxx> · Fri, 8 Nov 2024 21:32:26 +0200



    Dear All, 
    we have hit a serious performance regression
        going from 10.23 → 16.4 as far as tds_fdw (MS SQL) FDW is
        concerned. To cut the long story short, I recreated the good
        fast “old” (pgsql 10) setup on the same vm as the slow “new”
        (pgsql 16). Here is the bug report on github : 
    
      
              https://github.com/tds-fdw/tds_fdw/issues/371
              All environment on the two
                pgsql clusters is shared (freetds version, tds_fdw, gcc,
                llvm). Only thing differs are pgsql versions. The speed
                on the old pgsql 10.23 is about 10 to 20 times higher
                than pgsql 16.4 . Setting
                  client_min_messages TO debug3 does yield identical
                  output on the two systems. 

                
              The new pgsql 16.4 shows
                100% CPU usage during the query execution.

              
              I know we are pretty much
                alone with this, but it would be very nice if anyone
                could help, see smth we are missing or guide us via the
                right path.