| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Joe Conway <mail(at)joeconway(dot)com> |
| Cc: | David Olbersen <DOlbersen(at)stbernard(dot)com>, pgsql-novice <pgsql-novice(at)postgresql(dot)org> |
| Subject: | Re: String manipulation |
| Date: | 2003-07-29 01:21:13 |
| Message-ID: | 17030.1059441673@sss.pgh.pa.us |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-novice |
Joe Conway <mail(at)joeconway(dot)com> writes:
> SELECT substring(path from position(' ' in path) + 1) FROM (SELECT
> split_part( path, ':', 2 ) AS path FROM paths) AS ss;
> I could be wrong but I was thinking it would be more efficient to only
> calculate the function once.
Actually, the only thing you saved was writing out the split_part call
twice --- when the planner flattens the sub-select it expands each
reference to a sub-select output, so the split_part ends up getting
evaluated twice anyway. But the notational savings can be useful.
regards, tom lane
| From | Date | Subject | |
|---|---|---|---|
| Next Message | David Choo | 2003-07-29 02:25:35 | Unable to start postmaster |
| Previous Message | Joe Conway | 2003-07-28 23:17:30 | Re: String manipulation |