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    SubjectRe: [HACKERS] Improve lseek scalability v3

    Excerpts from Andres Freund's message of vie sep 16 14:27:33 -0300 2011:
    > Hi,
    > On Friday 16 Sep 2011 17:36:20 Matthew Wilcox wrote:

    > > Does the query planner need to know the exact number of bytes in the file,
    > > or is it after an order-of-magnitude? Or to-the-nearest-gigabyte?
    > It depends on where the information is used. For some of the uses it needs to
    > be exact (the assumed size is rechecked after acquiring a lock preventing
    > extension) at other places I guess it would be ok if the accuracy got lower
    > with bigger files (those files won't ever get bigger than 1GB).

    One other thing we're interested in is portability. I mean, even if
    Linux were to introduce a new hypothetical syscall that was able to
    return the file size at a ridiculously low cost, we probably wouldn't
    use it because it'd be Linux-specific. So an improvement of lseek()
    seems to be the best option.

    Álvaro Herrera <>
    The PostgreSQL Company - Command Prompt, Inc.
    PostgreSQL Replication, Consulting, Custom Development, 24x7 support
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