We have a similar timeseries database approaching 500m records. We partition the main tables (much like your events) into one year subsets, with a clustered index on timestamp for all but the live year.
https://blog.engineyard.com/2013/scaling-postgresql-performance-table-partitioning http://www.postgresql.org/docs/9.3/static/ddl-partitioning.html http://www.postgresql.org/docs/9.3/static/sql-cluster.html As discussed here previously, you can also improve performance using hardware - SSD'd vs spindles. Also note that tablespaces, with indexes on your faster drives & data on slower ones can improve performance. http://www.postgresql.org/docs/9.3/static/manage-ag-tablespaces.html Also make sure your db server is optimised for the database size & hardware configuration - like perhaps alloe fewer concurrent users, but more resources per user, or see what pgtune recommends. Should help your performance, in terms of underlying db efficiency & performance, rather than tweaking your actual queries. Brent Wood Programme leader: Environmental Information Delivery NIWA DDI: +64 (4) 3860529 Brent Wood Principal Technician - GIS and Spatial Data Management Programme Leader - Environmental Information Delivery +64-4-386-0529 | 301 Evans Bay Parade, Greta Point, Wellington | www.niwa.co.nz<http://www.niwa.co.nz> [NIWA]<http://www.niwa.co.nz> ________________________________________ From: pgsql-general-ow...@postgresql.org <pgsql-general-ow...@postgresql.org> on behalf of Jonathan Vanasco <postg...@2xlp.com> Sent: Saturday, September 27, 2014 9:02 AM To: PostgreSQL general Subject: [GENERAL] advice sought - general approaches to optimizing queries around "event streams" I have a growing database with millions of rows that track resources against an event stream. i have a few handfuls of queries that interact with this stream in a variety of ways, and I have managed to drop things down from 70s to 3.5s on full scans and offer .05s partial scans. no matter how i restructure queries, I can't seem to get around a few bottlenecks and I wanted to know if there were any tips/tricks from the community on how to approach them. a simple form of my database would be: -- 1k of create table stream ( id int not null primary key, ) -- 1MM of create table resource ( id int not null primary key, col_a bool, col_b bool, col_c text, ); -- 10MM of create table streamevent ( id int not null, event_timestamp timestamp not null, stream_id int not null references stream(id) ); -- 10MM of create table resource_2_stream_event( resource_id int not null references resource(id), streamevent_id int not null references streamevent(id) ) Everything is running off of indexes; there are no seq scans. I've managed to optimize my queries by avoiding joins against tables, and turning the stream interaction into a subquery or CTE. better performance has come from limiting the number of "stream events" ( which are only the timestamp and resource_id off a joined table ) The bottlenecks I've encountered have primarily been: 1. When interacting with a stream, the ordering of event_timestamp and deduplicating of resources becomes an issue. I've figured out a novel way to work with the most recent events, but distant events are troublesome using no limit, the query takes 3500 ms using a limit of 10000, the query takes 320ms using a limit of 1000, the query takes 20ms there is a dedicated index of on event_timestamp (desc) , and it is being used according to the planner... finding all the records is fine; merging-into and sorting the aggregate to handle the deduplication of records in a stream seems to be the issue (either with DISTINCT or max+group_by) 2. I can't figure out an effective way to search for a term against an entire stream (using a tsquery/gin based search) I thought about limiting the query by finding matching resources first, then locking it to an event stream, but: - scanning the entire table for a term takes about 10 seconds on an initial hit. subsequent queries for the same terms end up using the cache, and complete within 20ms. I get better search performance by calculating the event stream, then searching it for matching documents, but I still have the performance issues related to limiting the window of events i didn't include example queries, because I'm more concerned with the general approaches and ideas behind dealing with large data sets than i am with raw SQL right now. i'm hoping someone can enlighten me into looking at new ways to solve these problems. i think i've learned more about postgres/sql in the past 48hour than I have in the past 15 years, and I'm pretty sure that the improvements I need will come from new ways of querying data , rather than optimizing the current queries. -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
