On 08/07/2019 18:29, Tom Lane wrote: > Andrew Gierth <andrew@xxxxxxxxxxxxxxxxxxxx> writes: >> "Tom" == Tom Lane <tgl@xxxxxxxxxxxxx> writes: >> Tom> Two I'd particularly draw your attention to are >> Tom> join_collapse_limit and from_collapse_limit --- if you set both to >> Tom> 1, that'll effectively disable searching for a good join order, >> Tom> causing the join order to match the syntactic structure of the >> Tom> FROM clause. For instance "FROM a,b,c" will always be done by >> Tom> joining a to b first > >> FROM a,b,c can always be planned in any join order. > > Ah, right, -ENOCAFFEINE. What from_collapse_limit really does is > prevent flattening sub-SELECTs when doing so would add more join-order > freedom in the parent query. But ignoring sub-SELECTs, using explicit > JOIN syntax with join_collapse_limit=1 will let you control the > join order. > > regards, tom lane > Thanks for the clarification. I really appreciate taking the time to provide such in depth info about my query!
