I came across an odd performance problem in some legacy Oracle PL/SQL code that I was able to resolve by replacing an update statement with a merge. I abstracted the essence of the problem using the simple table from my last blog post, plus a summary table. Unlike in the previous article, the simple update did not work very well. I made a short Twitter thread on my findings…
Odd performance problem abstracted to simple dm. UPDATE grouped summary column with no indexes inefficient #brenThread #oracle ? 1/3 pic.twitter.com/ht9hZVBXt9
— Brendan Furey (@BrenPatF) October 8, 2017
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 – 64bit Production