On 12/4/10 8:42 AM, Tom Lane wrote:
> John Papandriopoulos<dr(dot)jpap(at)gmail(dot)com> writes:
>> I've recreated the same example with just one parent table, and 4096 child tables.
>> SELECT query planning is lightning fast as before; DELETE and UPDATE cause my machine to swap.
>> What's different about DELETE and UPDATE here?
> Hmm. Rules? Triggers? You seem to be assuming the problem is at the
> planner stage but I'm not sure you've proven that.
My example starts off with a new database (e.g. createdb ptest).
I set up my schema using a machine generated SQL file  that simply
creates a table
create table ptest ( id integer );
and N = 0..4095 inherited children
create table ptest_N (
check ( (id >= N_min) and (id <= N_max) )
) inherits (ptest);
that split the desired id::integer range into N buckets, one for each of
the N partitions.
I then immediately run a query-plan using EXPLAIN that exhibits the
described behavior: super-fast plan for a SELECT statement, without
swapping, and memory intensive (swapping) plans for DELETE and UPDATE.
There are no triggers, no rules, no plpgsql functions, no indexes and no
Is there a more simple example that might help me convince you that
we're exercising just the planner stage?
In response to
pgsql-performance by date
|Next:||From: Mladen Gogala||Date: 2010-12-04 21:58:10|
|Subject: Re: Query-plan for partitioned UPDATE/DELETE slow and swaps
vmem compared to SELECT|
|Previous:||From: felix||Date: 2010-12-04 19:45:19|
|Subject: Re: Update problem on large table|