On 27/10/15 11:37, Jim Nasby wrote:
On 10/25/15 9:36 PM, Kisung Kim wrote:
I want to explain for our clients that PG's update performance is
comparable to Oracle's.
There's really only 2 ways you can answer that. You can either
handwave the question away ("Yes, update performance is comparable."),
or you have to do actual benchmarking. Trying to answer this from a
theoretical standpoint is completely useless because there's an absurd
number of things that will affect this:
Number of columns
Data types
Size of overall transaction
Percent of transactions that roll back
Size of table
What % of table is updated every day
Underlying hardware
What OS the database is running on
What filesystem the database is running on
... and that's just off the top of my head.
Or to look at it another way, I guarantee you can create a scenario
where Postgres beats the pants off Oracle, *or vice versa*. So you
have to either go with an answer along the lines of "For most
workloads the performance of both databases is similar." or you have
to benchmark the actual application in question. Most performance
issues you find will probably be correctable with a moderate amount of
work.
To me, the real tradeoff between Postgres and Oracle (or any other
commercial database) is whether you'd rather spend money on expert
employees or software contracts.
And of course, on how you alter the tuning parameters in
postgresql.conf, like temp_buffers and work_mem. The 'correct' values
will depend on your workload and amount of RAM etc.
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