Save and restore query plans in PostgreSQL

Rationale

sr_plan looks like Oracle Outline system. It can be used to lock the execution plan. It is necessary if you do not trust the planner or able to form a better plan.

Build and install

make USE_PGXS=1
make USE_PGXS=1 install

and modify your postgres config:

shared_preload_libraries = 'sr_plan'

Usage

Install the extension in your database:

CREATE EXTENSION sr_plan;

If you want to save the query plan is necessary to set the variable:

set sr_plan.write_mode = true;

Now plans for all subsequent queries will be stored in the table sr_plans. Don't forget that all queries will be stored including duplicates.

Make an example query:

select query_hash from sr_plans where query_hash=10;

Disable saving the plan for the query:

set sr_plan.write_mode = false;

Enable it:

update sr_plans set enable=true;

After that, the plan for the query will be taken from the sr_plans.

In addition sr plan allows you to save a parameterized query plan. In this case, we have some constants in the query are not essential. For the parameters we use a special function _p (anyelement) example:

select query_hash from sr_plans where query_hash=1000+_p(10);

If we keep the plan for the query and enable it to be used also for the following queries:

select query_hash from sr_plans where query_hash=1000+_p(11);
select query_hash from sr_plans where query_hash=1000+_p(-5);