Very long time to execute and Update, suggestions? - Mailing list pgsql-performance

Hi all,

   I have a table with a little over 200,000 columns in it that I need
to update using a regular expression. I admit that though I am not a
beginner and postgres, I am also far from an expert. :p

   I tried to create an Index that would optimize the UPDATE but I may
have made an error in how I built it. Here is the table structure, the
index I tried to create and an 'EXPLAIN ANALYZE' of the UPDATE (though I
  am still just now learning how to use 'EXPLAIN').

tle-bu=> \d file_info_3
                             Table "public.file_info_3"
      Column      |         Type         |                Modifiers
-----------------+----------------------+-----------------------------------------
  file_group_name | text                 | not null
  file_group_uid  | bigint               | not null
  file_mod_time   | bigint               | not null
  file_name       | text                 | not null
  file_parent_dir | text                 | not null
  file_perm       | text                 | not null
  file_size       | bigint               | not null
  file_type       | character varying(2) | not null default
'f'::character varying
  file_user_name  | text                 | not null
  file_user_uid   | bigint               | not null
  file_backup     | boolean              | not null default true
  file_display    | boolean              | not null default false
  file_restore    | boolean              | not null default false
Indexes:
     "file_info_3_display_idx" btree (file_type, file_parent_dir, file_name)

   Here is the EXPLAIN:

tle-bu=> EXPLAIN ANALYZE UPDATE file_info_3 SET file_backup='f' WHERE
file_parent_dir~'^/home' OR (file_parent_dir='/' AND file_name='home');
                                                       QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------
  Seq Scan on file_info_3  (cost=0.00..7770.00 rows=1006 width=206)
(actual time=1050.813..5648.462 rows=67835 loops=1)
    Filter: ((file_parent_dir ~ '^/home'::text) OR ((file_parent_dir =
'/'::text) AND (file_name = 'home'::text)))
  Total runtime: 68498.898 ms
(3 rows)

   I thought that it would have used the index because 'file_parent_dir'
and 'file_name' are in the index but is I am reading the "EXPLAIN"
output right it isn't but is instead doing a sequencial scan. If that is
the case, how would I best built the index? Should I have just used the
'file_parent_dir' and 'file_name'?

   Thanks all!!

Madison

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Madison Kelly (Digimer)
TLE-BU, The Linux Experience; Back Up
http://tle-bu.thelinuxexperience.com
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