On 08/07/2019 01:46, Rob Sargent wrote: > > >> On Jul 7, 2019, at 5:22 PM, Tom Mercha <mercha_t@xxxxxxxxxxx> wrote: >> >> Hi All >> >> As we know, a query goes through number of stages before it is executed. >> One of these stages is query optimization (QO). >> >> There are various parameters to try and influence optimizer decisions >> and costs. But I wanted to measure the effect of such a stage by turning >> it off completely and I can't find such a parameter which explicitly >> does that. Then I could execute a query to get the effect of "QO active >> and "QO inactive" and compare. >> >> Obviously, I know well what the results would generally look like but I >> am just interested in measuring the differences for various types of >> queries. I am also aware that this is a simple comparison - there are >> more interesting comparisons to perform with QO tweaks, but right now I >> am interested in something basic. >> >> So how would one shut down QO? Or at least, obtaining the guarantee of >> generating the worst plan possible, ideally without touching many >> parameters? >> >> Best, >> Tom > > Drop all indices? > Sorry, maybe my question wasn't clear enough. A query can be rewritten in various ways by applying rules and costs of relational algebra operators, as well as their parallelisation. I am talking about turning off this query optimization, so I am already assuming that indexes aren't present.
