R17 on spinning disk faster than PostgreSQL on SSD

Re:R17 on spinning disk faster than PostgreSQL on SSD by matthewnourse on Monday August 15, 2011 @11:56PM (#2889801)

Sure, here it is:

         name          |                                               current_setting

-----------------------+-------------------------------------------------------------------------------------------------------------

version | PostgreSQL 9.0.4 on x86_64-pc-linux-gnu, compiled by GCC gcc-4.4.real (Ubuntu 4.4.3-4ubuntu5) 4.4.3, 64-bit

external_pid_file | /var/run/postgresql/9.0-main.pid

lc_collate | en_AU.utf8

lc_ctype | en_AU.utf8

log_line_prefix | %t

max_connections | 100

max_stack_depth | 2MB

port | 5432

server_encoding | UTF8

shared_buffers | 32MB

ssl | on

TimeZone | localtime

unix_socket_directory | /var/run/postgresql

(13 rows)

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Re:R17 on spinning disk faster than PostgreSQL on SSD by jpitz on Tuesday August 16, 2011 @12:03AM (#2889824)

lc_collate | en_AU.utf8

lc_ctype | en_AU.utf8

server_encoding | UTF8

Does r17 use utf-8?

shared_buffers | 32MB

Thats mean! :D

Should be 3GB on that machine. effective_cache_size ought to be 10-12GB ish.

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Re:R17 on spinning disk faster than PostgreSQL on SSD by matthewnourse on Tuesday August 16, 2011 @12:16AM (#2889867)

Cool, thanks!

Will alter and re-run in a few minutes.

r17 supports only UTF8 strings but compares with strcmp/strcasecmp/memcmp depending on the situation. Would you like a different collation for PostgreSQL too?

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Re:R17 on spinning disk faster than PostgreSQL on SSD by jpitz on Tuesday August 16, 2011 @12:32AM (#2889902)

I've no idea how those behave with utf8 data.

I'm more interested in what the memory settings do to the benchmark. After that, I'd want to see EXPLAIN ANALYZE.

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Re:R17 on spinning disk faster than PostgreSQL on SSD by matthewnourse on Tuesday August 16, 2011 @08:11PM (#2893433)

They work as expected for English. They "work" for languages with characters outside the English set, but they order based on ASCII byte values rather than the order expected by native speakers. Proper collation is a TODO for r17.

I made these changes to postgresql.conf and restarted postgresql:

random_page_cost = 1.0

effective_cache_size = 11GB

shared_buffers = 3GB

The times for load, index and the queries were about the same as for the published run.

My apologies, I should have said earlier & in the blog that PostgreSQL is _CPU bound_ even before I made these changes. Next time I will also track CPU and disk usage and publish those for more clarity.

I've re-run EXPLAIN and done a bit more digging than before, looks like PostgreSQL does not use the "username" index to do the GROUP BY, I suspect it's related to this: http://archives.postgresql.org/pgsql-bugs/2008-02/msg00220.p...

Thanks again!

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