Re: Generic function for partitioning function?

On Wed, Sep 4, 2013 at 2:10 AM, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> wrote:

> On Tuesday, September 3, 2013, Gregory Haase wrote:
>
>> I am working on a date-based partitioning framework and I would really
>> like to have a single function that could be used as trigger for any table
>> that needs to be partitioned by day. I am working in a rails environment,
>> so every table has a created_at datetime field.
>>
>> I created my generic function:
>>
>> create or replace function day_partition_insert_trigger()
>> returns trigger as $$
>> declare
>> ins_tbl varchar;
>> begin
>> ins_tbl := TG_TABLE_SCHEMA || '.' || TG_TABLE_NAME || '_' ||
>> to_char(NEW.created_at,'YYYYMMDD');
>> execute 'insert into '|| ins_tbl ||' select ($1).*' using NEW;
>> return null;
>> end;
>> $$ language plpgsql;
>>
>> ...
>>
>
>
>> I began to wonder if there would be a performance degradation, so I
>> changed the testdailytwo trigger function the typical if, elsif described
>> in the partitioning documentation and then ran pgbench against both tables.
>>
>> I noticed that with 7 partitions, the if, elsif was slightly faster
>> (~8%). However, when adding 30 partitions, the if, elsif version became
>> slower. I'd sort of expected this.
>>
>
> Did you try an if, elsif, version structured like a binary search rather
> than a linear search?
>
> Also, did you try them with a \copy rather than insert in a loop?
>
> Cheers,
>
> Jeff
>
>>

I experimented with trigger based inserts and rule based inserts.
In my case I insert many rows at a time and in that case, rule based
inserts performed better.

Here is an example from me and it is based on the online postgres documents.

*CREATE TABLE test*
(
id integer,
ts timestamp without time zone,
value real
);

-- create each partition, example for a single one
CREATE TABLE test_partition_2013_08_16
(
CONSTRAINT test_partition_2013_08_16_timestamp_check CHECK (ts >=
'2013-08-16'::date AND ts < '2013-08-17'::date)
)
*INHERITS (test)*;

CREATE INDEX idx_test_2013_08_16_ts ON test_partition_2013_08_16
USING btree
(ts);

-- for each partition create a rule like the following:
CREATE OR REPLACE RULE test_partition_2013_08_16_rule AS
ON INSERT TO test
WHERE new.ts >= '2013-08-16'::date AND new.ts < '2013-08-17'::date DO
INSTEAD INSERT INTO test_partition_2013_08_16 (id, ts, value)
VALUES (new.id, new.ts, new.value);

I have create a function/procedure that creates and drops the partitions
for me and run it from crontab.

Hope this helps,
- Gummi