Took some time until I could try out this... But as soon I want to create the fcuntion based index it tells me:
Error : ERROR: functions in index expression must be marked IMMUTABLE Deleteing the sort function and recreating with the IMMUTABLE attribute gives the same error.. Here the functions: CREATE FUNCTION btrsort_nextunit(text) RETURNS text AS $$ SELECT CASE WHEN $1 ~ '^[^0-9]+' THEN COALESCE( SUBSTR( $1, LENGTH(SUBSTRING($1 FROM '[^0-9]+'))+1 ), '' ) ELSE COALESCE( SUBSTR( $1, LENGTH(SUBSTRING($1 FROM '[0-9]+'))+1 ), '' ) END $$ LANGUAGE SQL IMMUTABLE; CREATE FUNCTION btrsort(text) RETURNS text AS $$ SELECT CASE WHEN char_length($1)>0 THEN CASE WHEN $1 ~ '^[^0-9]+' THEN RPAD(SUBSTR(COALESCE(SUBSTRING($1 FROM '^[^0-9]+'), ''), 1, 12), 12, ' ') || btrsort(btrsort_nextunit($1)) ELSE LPAD(SUBSTR(COALESCE(SUBSTRING($1 FROM '^[0-9]+'), ''), 1, 12), 12, ' ') || btrsort(btrsort_nextunit($1)) END ELSE $1 END ; $$ LANGUAGE SQL IMMUTABLE; And the index creation: create index port_name_btrsort_index on port(btrsort(name)); Which should speed up my query: select * from port where name not like '%Z' order by btrsort(name) asc cheers richard On Sat, 17 Dec 2011 16:16:07 +0100, Filip RembiaĆkowski wrote: > If you use btrsort(column) from the example, you can just create a > functional index on this expression. > > CREATE INDEX mytable_column_btrsort_idx ON mytable( btrsort(column) ); > > this can help. > > > > > > 2011/12/17 Richard Klingler <rich...@klingler.net>: >> Morning... >> >> What is the fastest way to achieve natural ordering from queries? >> >> I found a function at: >> http://2kan.tumblr.com/post/361326656/postgres-natural-ordering >> >> But it increases the query time from around 0.4msecs to 74msecs... >> Might be not much if occasional queries are made..but I use it for >> building >> up a hierarchical tree menu in a web application where every msecs >> counts (o; >> >> >> cheers >> richard >> >> >> -- >> Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) >> To make changes to your subscription: >> http://www.postgresql.org/mailpref/pgsql-sql > > -- > Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-sql -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql