Re: sum of all values

Madison Kelly wrote:
> Hi all,
>
> Is there a fast(er) way to get the sum of all integer values for a
> certain condition over many thousands of rows? What I am currently doing
> is this (which takes ~5-10sec.):

OK, I'm assuming you've configured PG to your satisfaction and this is
the only query giving you problems.

> SELECT SUM (a.file_size) FROM file_info_1 a, file_set_1 b WHERE
> a.file_name=b.fs_name AND a.file_parent_dir=b.fs_parent_dir AND
> a.file_type=b.fs_type AND b.fs_backup='t';

You'll want to run EXPLAIN ANALYSE SELECT SUM... and post the output of
that, although the query looks straightforward enough.

> Here are the schemas, in case they help:
>
> tle-bu=> \d file_info_1 Table "public.file_info_1"
> Column | Type | Modifiers
> -----------------+---------+----------------------------
> file_acc_time | bigint | not null
> file_group_name | text | not null
> file_group_uid | integer | 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 | text | not null default 'f'::text
> file_user_name | text | not null
> file_user_uid | integer | not null
> Indexes:
> "file_info_1_display_idx" btree (file_parent_dir, file_name, file_type)
> "file_info_1_search_idx" btree (file_parent_dir, file_name, file_type)
>
> tle-bu=> \d file_set_1 Table "public.file_set_1"
> Column | Type | Modifiers
> ---------------+---------+----------------------------
> fs_backup | boolean | not null default true
> fs_display | boolean | not null default false
> fs_name | text | not null
> fs_parent_dir | text | not null
> fs_restore | boolean | not null default false
> fs_type | text | not null default 'f'::text
> Indexes:
> "file_set_1_sync_idx" btree (fs_parent_dir, fs_name, fs_type)

1. WHERE ARE YOUR PRIMARY KEYS???
2. Why do you have two identical indexes on file_info_1
3. WHERE ARE YOUR PRIMARY KEYS???
4. Am I right in thinking that always, file_name==fs_name (i.e. they
represent the same piece of information) and if so, why are you storing
it twice? Same for _parent_dir too
5. file_type/fs_type are being held as unbounded text? Not an index into
some lookup table or a varchar(N)?

Can you explain what you're trying to do here - it might be you want to
alter your database design.
--
Richard Huxton
Archonet Ltd