Re: pg_read_file() with virtual files returns empty string

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Joe Conway <mail(at)joeconway(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgreSQL(dot)org>
Subject: Re: pg_read_file() with virtual files returns empty string
Date: 2020-06-28 22:00:16
Views: Raw Message | Whole Thread | Download mbox | Resend email
Lists: pgsql-hackers

Joe Conway <mail(at)joeconway(dot)com> writes:
> All good stuff -- I believe the attached checks all the boxes.

Looks okay to me, except I think you want

! if (bytes_to_read > 0)

to be

! if (bytes_to_read >= 0)

As it stands, a zero request will be treated like -1 (read all the
rest of the file) while ISTM it ought to be an expensive way to
read zero bytes --- perhaps useful to check the filename and seek
offset validity?

> The intention here seems to be that if you pass bytes_to_read = -1 with a
> negative offset, it will give you the last offset bytes of the file.

I think it's just trying to convert bytes_to_read = -1 into an explicit
positive length-to-read in all cases. We don't need that anymore with
this code, so dropping it is fine.

regards, tom lane

In response to


Browse pgsql-hackers by date

  From Date Subject
Next Message Andy Fan 2020-06-29 00:04:35 Re: Commitfest 2020-07
Previous Message Tom Lane 2020-06-28 19:48:04 Revert workarounds for unportability of printf %.*s format?