Re: surprisingly slow creation of gist index used in exclude constraint

On 14/05/2020 21:31, Tom Lane wrote:
> Chris Withers <chris(at)withers(dot)org> writes:
>> It has 4.1 million rows in it and while importing the data only
>> takes a couple of minutes, when I did a test load into the new
>> cluster, building the mkt_profile_period_col1_col4_col2_chan_excl
>> index for the exclude constraint took 15 hours.
>
> Don't recall for sure, but I think GIST index build is sensitive
> to the maintenance_work_mem setting; did you have that cranked up?

postgres=# show maintenance_work_mem;
maintenance_work_mem
----------------------
2GB
(1 row)

Would it be worth turning that up more? The server has ~130GB memory.

>> - failing that, what can I do to import and then create the index
>> in the background?
>
> CREATE INDEX CONCURRENTLY, perhaps.

How would I bring this into play with respect to the dump and load
cycle? Is there an option to pg_dump or something else I should use or
is this a case of awk'ing the create index in the dump?

Chris