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Thread: Creating Empty Index

Creating Empty Index

From
"naman.iitb"
Date:
Hello

Is there a way by which we can create an empty index on a relation and later
fill it manually by inserting tuples.

I want to know how it can be done in Postgresql code.

Thanks in advance





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Re: Creating Empty Index

From
Andrew Dunstan
Date:
On 11/01/2013 02:11 AM, naman.iitb wrote:
> Hello
>
> Is there a way by which we can create an empty index on a relation and later
> fill it manually by inserting tuples.
>
> I want to know how it can be done in Postgresql code.
>
> Thanks in advance
>


What exactly would be the point? Indexes are automatically maintained by 
postgres. Something that isn't doesn't seem to me to qualify for the 
description of "index".

cheers

andrew

Re: Creating Empty Index

From
Michael Paquier
Date:
On Sat, Nov 2, 2013 at 10:28 PM, Andrew Dunstan <andrew@dunslane.net> wrote:
> What exactly would be the point? Indexes are automatically maintained by
> postgres. Something that isn't doesn't seem to me to qualify for the
> description of "index".
Perhaps an index without data that could be used by the planner for
automatic query tuning to evaluate how a query could run if the index
exists? Like the concept of hypothetical indexes or something like the
possibility to do a CREATE/ALTER INDEX ... WITH [ NO ] DATA.
-- 
Michael

Re: Creating Empty Index

From
Tom Lane
Date:
Michael Paquier <michael.paquier@gmail.com> writes:
> On Sat, Nov 2, 2013 at 10:28 PM, Andrew Dunstan <andrew@dunslane.net> wrote:
>> What exactly would be the point? Indexes are automatically maintained by
>> postgres. Something that isn't doesn't seem to me to qualify for the
>> description of "index".

> Perhaps an index without data that could be used by the planner for
> automatic query tuning to evaluate how a query could run if the index
> exists? Like the concept of hypothetical indexes or something like the
> possibility to do a CREATE/ALTER INDEX ... WITH [ NO ] DATA.

But we already provide support for hypothetical indexes via planner
plugins.  Why would you need an actual empty index underlying that?

I agree with Andrew that the use-case for this hasn't been explained.
        regards, tom lane

Re: Creating Empty Index

From
Michael Paquier
Date:
On Sun, Nov 3, 2013 at 3:01 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Michael Paquier <michael.paquier@gmail.com> writes:
>> On Sat, Nov 2, 2013 at 10:28 PM, Andrew Dunstan <andrew@dunslane.net> wrote:
>>> What exactly would be the point? Indexes are automatically maintained by
>>> postgres. Something that isn't doesn't seem to me to qualify for the
>>> description of "index".
>
>> Perhaps an index without data that could be used by the planner for
>> automatic query tuning to evaluate how a query could run if the index
>> exists? Like the concept of hypothetical indexes or something like the
>> possibility to do a CREATE/ALTER INDEX ... WITH [ NO ] DATA.
>
> But we already provide support for hypothetical indexes via planner
> plugins.  Why would you need an actual empty index underlying that?
Using only the planner hook? Forgive my lack of knowledge of the
planner, but this does not seem really straight-forward :)

One of the only documentation I found about hypothetical indexes was
this tutorial of PGCon 2010:
http://www.inf.puc-rio.br/~postgresql/conteudo/projeto1/Tutorial9/TUTORIAL_9_0_1.pdf
But in this case the grammar of CREATE INDEX has been modified, so
core code was changed as well.

Of course if Naman has something else in mind...
-- 
Michael