Oops! spam_from_postgresql_general@xxxxxxxxxxxx (Phil Endecott) was seen spray-painting on a wall:I have a single database with one schema per user. Each user has a handful of tables, but there are lots of users, so in total the database has thousands of tables.
If you've got tens of thousands of relations, the tab completion code has to draw the whole list of relations from pg_class into memory and "marshal" it into a form usable by GNU Readline. THAT is what you're seeing slow down. As the number of tables, n, grows, the cost of that grows with order of complexity O(n).
Actual queries on actual tables won't be slow; they will look up relation names directly in pg_class, and presumably go from there to get the file name(s) on the filesystem, which each represent operations of complexity of order O(n log n). Which remains fast even if there are millions of tables.
I guess you mean O(log n) in the second paragraph (Which would imply that there is an index on relname for pg_class). If the complexity was O(n log n), it would be more complex/slower than an O(n) algorithm, and
therefore slower (or, at least, it would scale worse) than the tab-completion code ;-)
greetings, Florian Pflug
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