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.
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.