Re: Faster distinct query?
| От | Israel Brewster |
|---|---|
| Тема | Re: Faster distinct query? |
| Дата | |
| Msg-id | 6D98FC61-3916-4841-9A5F-E23E981E73DA@alaska.edu обсуждение исходный текст |
| Ответ на | Re: Faster distinct query? ("David G. Johnston" <david.g.johnston@gmail.com>) |
| Список | pgsql-general |
On Sep 22, 2021, at 12:20 PM, David G. Johnston <david.g.johnston@gmail.com> wrote:On Wed, Sep 22, 2021 at 1:05 PM Israel Brewster <ijbrewster@alaska.edu> wrote:To work around the issue, I created a materialized view that I can update periodically, and of course I can query said view in no time flat. However, I’m concerned that as the dataset grows, the time it takes to refresh the view will also grow (correct me if I am wrong there).I'd probably turn that index into a foreign key that just ensures that every (station,channel) that appears in the data table also appears on the lookup table. Grouping and array-ifying the lookup table would be trivial. Either modify the application code or add a trigger to populate the lookup table as needed.
Makes sense. I was actually considering this approach (albeit without the foreign key - that’s a nice additional safety measure), but was concerned about the overhead that adding said trigger would have on inserts - thus my thought to try the materialized view. As a reference, this database is receiving 1Hz data from around 170 stations, with up to three channels of data per station. So something like 350-500 inserts per second, although the data is “grouped” into 10 minute batches. I’ll give it another look.
The parentheses around channel in "array_agg(distinct(channel))" are unnecessary - you are invoking composite-type syntax, which is ignored in the single column case unless you write the optional ROW keyword, i.e., distinct ROW(channel)
Good information, thanks!
David J.
---
Israel Brewster
Software Engineer
Alaska Volcano Observatory
Geophysical Institute - UAF
2156 Koyukuk Drive
Fairbanks AK 99775-7320
Software Engineer
Alaska Volcano Observatory
Geophysical Institute - UAF
2156 Koyukuk Drive
Fairbanks AK 99775-7320
Work: 907-474-5172
cell: 907-328-9145
cell: 907-328-9145
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