Re: index ops for _int4 and trees?
Oh,
I forgot that without any contrib you can select rows whose papth to the root {1,2,3}:
select * from test where lineage[1:3] = '{1,2,3}';
but the gist indexing (intarray) performs a significant speed increase.
BTW, lineage represents egde-list of a directed graph or a tree ?
insert into test (id,lineage) values ('8','{1,2,3}');
------------------------------------------------|-^
insert into test (id,lineage) values ('9','{1,3,7}');
It seems to me that node 3 can be accessed from both node 1 and node 3 directly, or it's just a mistake?
----- Original Message -----
From: "Gyozo Papp" <pgerzson@freestart.hu>
To: "PostgreSQL-General" <pgsql-general@postgresql.org>; "Lincoln Yeoh" <lyeoh@pop.jaring.my>
Sent: 2001. �prilis 15. 13:23
Subject: Re: [GENERAL] index ops for _int4 and trees?
Hello,
have a look at contrib/intarray directory!
There is a pretty good index-support for one-dimensional integer array - solution for your 1st question.
... and it also includes two simple operator @ (= 'contains' similiar to AND) and && ( = 'overlap' similiar to OR) to check array values against an other array.
There is a short README.intarray file telling you what to do.
There is another contrib in contrib/array for more support to check array values. But I don't know this contibution can profit from the other's index technique.
After you 've installed these contribs your query can be written:
select * from test where lineage like '{1,2,3,%';
select * from test where lineage[1:3] @ '{1,2,3}';
I think these satisfy you.
Best,
Papp Gyozo
- pgerzson@freestart.hu
----- Original Message -----
From: "Lincoln Yeoh" <lyeoh@pop.jaring.my>
To: "PostgreSQL-General" <pgsql-general@postgresql.org>
Sent: 2001. m�jus 15. 10:20
Subject: [GENERAL] index ops for _int4 and trees?
Show quoted text
Hi,
Say I have the following table:
create table test (
id int,
lineage integer[]
);insert into test (id,lineage) values ('8','{1,2,3}');
insert into test (id,lineage) values ('9','{1,3,7}');
insert into test (id,lineage) values ('10','{1,2,3}');
insert into test (id,lineage) values ('11','{1,2,3,10}');
insert into test (id,lineage) values ('12','{1,3,7,9}');1) How do I create an index on integer[] aka _int4?
2) Is it possible to do something similar to the following select?
select * from test where lineage like '{1,2,3,%';
I'm basically using this as a method of fetching rows in a particular
branch of a whole tree, without having to do recursion and multiple selects.If 1 or 2 are not possible then I'll stick with using text and converting
ids to zeropadded hexadecimal <sigh>.I'm thinking that there should be a quick way to do branches and trees,
after all there's a btree index type, so... ;).Using text works but is rather crude, any working suggestions?
Thanks,
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At 06:29 PM 15-05-2001 +0200, Gyozo Papp wrote:
Oh,
I forgot that without any contrib you can select rows whose papth to the
root {1,2,3}:
select * from test where lineage[1:3] = '{1,2,3}';
but the gist indexing (intarray) performs a significant speed increase.
Thanks.
BTW, lineage represents egde-list of a directed graph or a tree ?
insert into test (id,lineage) values ('8','{1,2,3}');
------------------------------------------------|-^
insert into test (id,lineage) values ('9','{1,3,7}');
It seems to me that node 3 can be accessed from both node 1 and node 3
directly, or it's just a mistake?
It's a mistake in my example.
Aside but related:
Oleg Bartunov also mentioned that subset searches are possible with gist:
select * from table <TABLE> where <array_field> @ '{1,2,3}'
So I've asked him whether his work on gist indexing int arrays can be used
to do substring indexing on text, as a built-in to Postgresql.
I think it can be done. Then subtext_ops here we come :).
If not I'll resort to converting text characters to their code values and
stuffing them into int arrays. Ugly :). Not sure what happens when the
arrays get large.
Cheerio,
Link.