Hi Pavel,
What kind of example do you need? I cant give you the actual data I have in the table, but I can give you an example query and the schema attached below. From there, I would just put in 2 million rows worth 1.2 Gigs of data. Average size of the the extended columns (using the pg_column_size function) in bytes are:
guid: 33
name: 2.41
currency: 4
fields: 120.32
example query:
-- find duplicate records using a guid
select guid, array_agg(id) from orders group by guid;
example schema:
Table "public.things"
Column | Type | Modifiers | Storage | Stats target | Description
------------+-----------------------------+-----------------------------------------------------+----------+--------------+-------------
id | integer | not null default nextval('things_id_seq'::regclass) | plain | |
version | integer | not null | plain | |
created_at | timestamp without time zone | not null | plain | |
updated_at | timestamp without time zone | not null | plain | |
foo_id | integer | not null | plain | |
bar_id | integer | not null | plain | |
baz_id | integer | not null | plain | |
guid | character varying | not null | extended | |
name | character varying | not null | extended | |
price | numeric(12,2) | not null | main | |
currency | character varying | not null | extended | |
amount | integer | not null | plain | |
the_date | date | not null | plain | |
fields | hstore | | extended | |
Indexes:
"things_pkey" PRIMARY KEY, btree (id)
"things_foo_id_idx" btree (foo_id)
"things_bar_id_idx" btree (bar_id)
"things_baz_id_idx" btree (baz_id)
"things_guid_uidx" UNIQUE, btree (guid)
"things_lpad_lower_name_eidx" btree (lpad(lower(name::text), 10, '0'::text))
"things_price_idx" btree (price)
Foreign-key constraints:
"things_foo_id_fkey" FOREIGN KEY (foo_id) REFERENCES foos(id)
"things_bar_id_fkey" FOREIGN KEY (bar_id) REFERENCES bars(id)
"things_baz_id_fkey" FOREIGN KEY (baz_id) REFERENCES bazs(id)
Triggers:
timestamps_trig BEFORE INSERT OR UPDATE ON things FOR EACH ROW EXECUTE PROCEDURE timestamps_tfun()
Let me know if you need anything else.
Thanks,
On Mon, Aug 19, 2013 at 3:29 AM, Pavel Stehule <pavel.stehule@xxxxxxxxx> wrote:
RegardsHelloplease, can you send some example or test?
Pavel Stehule2013/8/19 Robert Sosinski <rsosinski@xxxxxxxxxxxxxxxxxxx>
When using array_agg on a large table, memory usage seems to spike up until Postgres crashes with the following error:2013-08-17 18:41:02 UTC [2716]: [2] WARNING: terminating connection because of crash of another server process
2013-08-17 18:41:02 UTC [2716]: [3] DETAIL: The postmaster has commanded this server process to roll back the current transaction and exit, because another server process exited abnormally and possibly corrupted shared memory.
2013-08-17 18:41:02 UTC [2716]: [4] HINT: In a moment you should be able to reconnect to the database and repeat your command.
I've definitely isolated it down to using array_agg, as when I changed the query to use string_agg, it worked fine. I also tried using array_agg on a few different queries, all yielding the same issue. Swapping in string_agg fixed the issue once more.
This particular table has over 2 million rows and is 1.2 Gigs, and when I ran the query while viewing htop, the virtual size of the Postgres process ballooned to 13.9G until crashing.The version of Postgres I am using is: PostgreSQL 9.2.4 on x86_64-unknown-linux-gnu, compiled by gcc (Ubuntu/Linaro 4.7.2-2ubuntu1) 4.7.2, 64-bitAny help would be much appreciated, thanks!
-Robert
