davidrowley

7 ms·

31.
by davidrowley 3y ago
> At least Oracle folks had enough at some point and introduced an "optimizer_ignore_hints" parameter [1], so all legacy hints that were added 20 years ago just get ignored - and the modern optimizer does a much better job gett
32.
by davidrowley 3y ago
(Postgres committer and blog author here) Personally, I don't have any objection to hints. The resolution of any statistics is never going to be high enough to always be accurate enough for all cases. I think it would be good to give
33.
by davidrowley 3y ago
There is a pg_hint_plan extension. I think the danger with hints is that they might only be correct when written. If the table sizes or data skew changes, they might make things worse. I don't have a link to hand, but last time I re
34.
by davidrowley 4y ago
(blog author here) Yes, thanks for raising this. I didn't manage to complete my analysis for the regression at 64MB work_mem before publishing the blog. I drew up my analysis on https://www.postgresql.org/message-id&#x
35.
by davidrowley 5y ago
If I remember correctly, SQL Server will convert NOT IN to anti-join. PostgreSQL currently does not do that due to NOT IN being incompatible with anti-joins in regards to NULL values. There's room for improvement there by detecting i
36.
by davidrowley 6y ago
The visibility map is just 1 bit per page. Vacuum sets these bits to "1" when it sees that all tuples on the page are visible to all transactions. i.e. all tuple xmins are <= the oldest running transaction and none of the tupl
37.
by davidrowley 6y ago
Index Only Scans are a thing in PostgreSQL, however, they may still need to visit the heap if the visibility map bit for the heap page indicates that the not all tuples on the heap page are visible to all transactions. When a high percenta