Обсуждение: Changing the result set to contain the cost of the optimizer's chosen plan
Changing the result set to contain the cost of the optimizer's chosen plan
От
Srinivas Karthik V
Дата:
Hello,
I am Srinivas and have been working inside PostgreSQL (mostly in the optimizer module and few times in the executor module). I would like to change PostgreSQL code such that it also returns the cost of the optimizer chosen plan to the Java program (through JDBC) as part of the result set. Srinivas Karthik V <skarthikv.iitb@gmail.com> writes:
> Specifically, I have a Java program which calls
> ResultSet rs = statement.executeQuery("explain select * from table");
> I would like to change PostgreSQL such that ResultSet rs should contain a
> field that contains also the cost of the optimizer chosen plan.
Why do you need to change anything? The cost is right there in the
first line of the result text. It might be easier to parse out if
you use one of EXPLAIN's intended-to-be-machine-readable output
formats, though.
regards, tom lane
Re: Changing the result set to contain the cost of the optimizer's chosen plan
От
Craig Ringer
Дата:
On 11 July 2016 at 23:29, Tom Lane <tgl@sss.pgh.pa.us> wrote:
Srinivas Karthik V <skarthikv.iitb@gmail.com> writes:
> Specifically, I have a Java program which calls
> ResultSet rs = statement.executeQuery("explain select * from table");
> I would like to change PostgreSQL such that ResultSet rs should contain a
> field that contains also the cost of the optimizer chosen plan.
Why do you need to change anything? The cost is right there in the
first line of the result text. It might be easier to parse out if
you use one of EXPLAIN's intended-to-be-machine-readable output
formats, though.
Yeah - if we were going to do this at all, it'd want to be output that decomposes _all_ the explain output into columns. But since we can emit json, xml, etc, I don't really see the point.
Re: Changing the result set to contain the cost of the optimizer's chosen plan
От
Srinivas Karthik V
Дата:
Hi Tom,
Yes, we indeed get the cost of the plan at the first line itself. Somehow, I missed this point. We just in fact implemented this functionality and its working. Thanks again. On Tue, Jul 12, 2016 at 6:43 AM, Craig Ringer <craig@2ndquadrant.com> wrote:
On 11 July 2016 at 23:29, Tom Lane <tgl@sss.pgh.pa.us> wrote:Srinivas Karthik V <skarthikv.iitb@gmail.com> writes:
> Specifically, I have a Java program which calls
> ResultSet rs = statement.executeQuery("explain select * from table");
> I would like to change PostgreSQL such that ResultSet rs should contain a
> field that contains also the cost of the optimizer chosen plan.
Why do you need to change anything? The cost is right there in the
first line of the result text. It might be easier to parse out if
you use one of EXPLAIN's intended-to-be-machine-readable output
formats, though.Yeah - if we were going to do this at all, it'd want to be output that decomposes _all_ the explain output into columns. But since we can emit json, xml, etc, I don't really see the point.--