Re: [SQL] using explain output within pgsql

On Sunday, July 10, 2011 11:54:10 am Uwe Bartels wrote:
> Hi,
>
> I'm starting up a datawarehouse with patitioning.
> my etl processes write directly into the corresponding partitions instead
> of using triggers.
>
> The reports I run in the datawarehouse are stored in a cache within the
> same database.
> Now I'd like to store besides the results the dependencies to the tables
> which were used to generate the report. with this information i could
> invalidate cache results for the tables I'm going to import with my etl
> processes.
>
> explain analyze gives me the information which table or patition is read
> from for each report. e.g
> explain analyze (FORMAT YAML) create table cache.report234 as select
> col1,col2,sum(clicks) from dwh.event_log_weekly where week >= '2011-06-27'
> and week <= '2011-07-11' group by col1,col2;
>
> now I'd like to store the output of explain analyze in a pgsql variable for
> further processing. that looks something like this.
>
> DO $$declare l_explain text;
> begin
> l_explain := explain analyze (FORMAT YAML) create table cache.report234 as
> select col1,col2,sum(clicks) from dwh.event_log_weekly where week >=
> '2011-06-27' and week <= '2011-07-11' group by col1,col2;
> select l_explain;
> end$$;
>
> But that doesn't work. I get a syntax error.

From here:
http://www.postgresql.org/docs/9.0/interactive/sql-explain.html

I believe you are looking for:
explain (ANALYZE, FORMAT YAML) create table...

>
> Does anybody has an idea how to retrieve the output of explain within pgsql
> and store this in a variable?
> An alternative would be any other way to extract the information about
> tables used by arbitrary sql statements.
>
> best regards,
> Uwe

--
Adrian Klaver
adrian(dot)klaver(at)gmail(dot)com