Re: performance for high-volume log insertion

On Wed, 22 Apr 2009, Glenn Maynard wrote:

> On Wed, Apr 22, 2009 at 8:19 AM, Stephen Frost <sfrost@snowman.net> wrote:
>> Yes, as I beleive was mentioned already, planning time for inserts is
>> really small.  Parsing time for inserts when there's little parsing that
>> has to happen also isn't all *that* expensive and the same goes for
>> conversions from textual representations of data to binary.
>>
>> We're starting to re-hash things, in my view.  The low-hanging fruit is
>> doing multiple things in a single transaction, either by using COPY,
>> multi-value INSERTs, or just multiple INSERTs in a single transaction.
>> That's absolutely step one.
>
> This is all well-known, covered information, but perhaps some numbers
> will help drive this home.  40000 inserts into a single-column,
> unindexed table; with predictable results:
>
> separate inserts, no transaction: 21.21s
> separate inserts, same transaction: 1.89s

are these done as seperate round trips?

i.e.
begin <send>
insert <send>
insert <send>
..
end <send>

or as one round trip?

i.e.
begin;insert;insert..;end

> 40 inserts, 100 rows/insert: 0.18s
> one 40000-value insert: 0.16s
> 40 prepared inserts, 100 rows/insert: 0.15s

are one of these missing a 0?

> COPY (text): 0.10s
> COPY (binary): 0.10s
>
> Of course, real workloads will change the weights, but this is more or
> less the magnitude of difference I always see--batch your inserts into
> single statements, and if that's not enough, skip to COPY.

thanks for this information, this is exactly what I was looking for.

can this get stored somewhere for reference?

David Lang