| From: | Sailesh Krishnamurthy <sailesh(at)cs(dot)berkeley(dot)edu> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Group-count estimation statistics |
| Date: | 2005-01-28 23:42:09 |
| Message-ID: | mjqwttxnmsu.fsf@drones.CS.Berkeley.EDU |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
>>>>> "Tom" == Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
Tom> The only real solution, of course, is to acquire cross-column
Tom> statistics, but I don't see that happening in the near
Tom> future.
Another approach is a hybrid hashing scheme where we use a hash table
until we run out of memory at which time we start spilling to disk. In
other words, no longer use SortAgg at all ..
Under what circumstances will a SortAgg consumer more IOs than a
hybrid hash strategy ?
--
Pip-pip
Sailesh
http://www.cs.berkeley.edu/~sailesh
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Tom Lane | 2005-01-29 00:24:40 | Re: [pgsql-hackers] Allow GRANT/REVOKE permissions to be applied to all schema |
| Previous Message | Andrew Dunstan | 2005-01-28 22:01:51 | Re: -HEAD on FreeBSD 6-CURRENT build failures |