On Tue, May 15, 2018 at 3:45 PM, legrand legrand <legrand_legr...@hotmail.com> wrote: > Would there be some functional or performances reasons to prefer jumbling to > hashing normalized plan text?
Using the text could produce different query IDs for the same plan if any information is displayed in the text format which can vary for reasons other than a plan change. I don't know if there are any, but what about, for example, the effect of GUCs on how timestamps are displayed? Or, much worse, what if a timer value creeps into the output somehow? Certainly, renaming a table is going to change the output. Even using a different table alias will change the output. Using the text could produce the same query ID for different plans if there's any relevant detail of the plan that's not shown in the text. Basically, I would be nervous about the idea of an EXPLAIN output that's required to reflect all and only the plan details that should be jumbled. The "normalized" option to EXPLAIN which you mentioned upthread doesn't exist today... -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
