Save and restore query plans in PostgreSQL

Build

Dependencies: >= Python 3.2, Mako, pycparser If you only have a Python you can use the virtual environment:

virtualenv env
source ./env/bin/activate
pip install -r ./requirements.txt

Then you need to generate C code and compiled it:

make USE_PGXS=1 genparser
make USE_PGXS=1
make USE_PGXS=1 install

and modify your postgres config:

shared_preload_libraries = 'sr_plan.so'

Usage

In your db:

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 requests will be stored in the table sr_plans. It must be remembered that all requests will be maintained including duplicates. Making an example query:

select query_hash from sr_plans where query_hash=10;

disable saving the query:

set sr_plan.write_mode = false;

Now verify that your query is saved:

select query_hash, enable, valid, query, explain_jsonb_plan(plan) from sr_plans;

explain_jsonb_plan function allows you to display explain execute the plan of which lies in jsonb. By default, all the plans are off, you need enable it:

update sr_plans set enable=true where query_hash=812619660;

(812619660 for example only) 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);