Обсуждение: performance of like queries

Hi List;

any suggestions for improving "LIKE '%text%'" queries?


Thanks in advance

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Kevin Kempter wrote:
> Hi List;
>
> any suggestions for improving "LIKE '%text%'" queries?

faster disks :)

take a look at pg_tgrm and tsearch2.

Sincerely,

Joshua D. Drake


>
>
> Thanks in advance
>
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On 10/2/07, Kevin Kempter <kevin@kevinkempterllc.com> wrote:
> Hi List;
>
> any suggestions for improving "LIKE '%text%'" queries?

http://www.depesz.com/index.php/2007/09/15/speeding-up-like-xxx/

kevin@kevinkempterllc.com (Kevin Kempter) writes:
> any suggestions for improving "LIKE '%text%'" queries?

If you know that the 'text' portion of that query won't change, then
you might create a partial index on the boolean condition.

That is,

  create index index_foo_text on my_table (tfield) where (tfield like '%text%');

I somehow doubt that is the case; more likely you want to be able to
search for:
   select * from my_table where tfield like '%this%';
   select * from my_table where tfield like '%that%';
   select * from my_table where tfield like '%the other thing%';

There are basically three choices, at that point:

1.  Get more memory, and hope that you can have all the data get
cached in memory.

2.  Get more better disk, so that you can scan the table faster on
disk.

3.  Look into tsearch2, which provides a full text search capability.
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