Wiki / Configuration Parameters

Specifies the method used to extend data files during bulk operations such as COPY. The first available option is used as the default, depending on the operating system: posix_fallocate (Unix) uses the standard POSIX interface for allocating disk space, but is missing on some systems. If it is present but the underlying file system doesn't support it, this option silently falls back to write_zeros. Current versions of BTRFS are known to disable compression when this option is used. This is the default on systems that have the function. write_zeros extends files by writing out blocks of zero bytes. This is the default on systems that don't have the function posix_fallocate. The write_zeros method is always used when data files are extended by 8 blocks or fewer.

English manual coverage begins with PostgreSQL 7.4. Source history and runtime observations have their own recorded version boundaries.

boot val

posix_fallocate

category

Resource Usage / Disk

context

sighup

documented

true

enumvals

posix_fallocate, write_zeros

extra desc

Unknown

lang

en

max val

Unknown

metadata version

18

min val

Unknown

name

file_extend_method

short desc

Selects the method used for extending data files.

source

pg-settings-source-snapshot

unit

Unknown

vartype

enum