Hi,
(CCing -hackers)
On 2018-09-24 12:22:28 -0700, legrand legrand wrote:
> I have found that explain on tables with many (hundreds) columns
> are slow compare to nominal executions.
Yea, colname_is_unique() (called via make_colname_unique()) is
essentially O(#total_columns) and rougly called once for each column in
a select list (or using or ...). IIRC we've hit this once when I was at
citus, too.
We really should be usign a more appropriate datastructure here - very
likely a hashtable. Unfortunately such a change would likely be a bit
too much to backpatch...
Greetings,
Andres Freund
