Re: [SQL] using explain output within pgsql

On 11/07/11 08:18, Pavel Stehule wrote:
> 2011/7/10 Uwe Bartels<uwe(dot)bartels(at)gmail(dot)com>:
>> Hi Pavel,
>>
>> is it posible to get this running even with dynamic sql?
>> I didn't write that. I'm using execute to run this create table ....
>>
> probably yes
>
> postgres=# do $$
> declare x text;
> begin
> execute e'explain(format yaml) select * from data where value = \'a\'' into x;
> raise notice '%', x;
> end;
> $$ language plpgsql;
> NOTICE: - Plan:
> Node Type: "Seq Scan"
> Relation Name: "data"
> Alias: "data"
> Startup Cost: 0.00
> Total Cost: 23.38
> Plan Rows: 5
> Plan Width: 46
> Filter: "((value)::text = 'a'::text)"
> DO
[...]

I find that I understand things better if I rephrase things, so I took
Pavel's code and converted it to use variables so I could see more
clearly what is happening.

I think using variables makes the use of 'execute' more understandable.

I hope this version is of value to to others, I have included all the
code required to run it as a working example.

CREATE TABLE data
(
id int,
value text
);

INSERT INTO
data (id, value)
VALUES
(1, 'a'),
(2, 'b');

do $$
declare
v_sql_query text;
v_sql_explain text;
v_result text;
begin
v_sql_query :=e'SELECT * FROM data d WHERE value = \'a\'';
v_sql_explain :=e'EXPLAIN(FORMAT YAML) ' || v_sql_query;
execute v_sql_explain into v_result;
raise notice 'v_result: %', v_result;
end;
$$ language plpgsql;

Cheers,
Gavin