Re: Key/Value reference table generation: INSERT/UPDATE performance - Mailing list pgsql-performance

On Tue, 22 May 2007 10:23:03 +0200, valgog <valgog@gmail.com> wrote:

> I found several post about INSERT/UPDATE performance in this group,
> but actually it was not really what I am searching an answer for...
>
> I have a simple reference table WORD_COUNTS that contains the count of
> words that appear in a word array storage in another table.

    Mmm.

    If I were you, I would :

    - Create a procedure that flattens all the arrays and returns all the
words :

PROCEDURE flatten_arrays RETURNS SETOF TEXT
FOR word_array IN SELECT word_array FROM your_table LOOP
    FOR i IN 1...array_upper( word_array ) LOOP
        RETURN NEXT tolower( word_array[ i ] )

So, SELECT * FROM flatten_arrays() returns all the words in all the arrays.
To get the counts quickly I'd do this :

SELECT word, count(*) FROM flatten_arrays() AS word GROUP BY word

You can then populate your counts table very easily and quickly, since
it's just a seq scan and hash aggregate. One second for 10.000 rows would
be slow.