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#!/bin/sh
# retrieve a WAL file from a pg_receivewal archive
#
# Copyright (C) 2021-2022 Christoph Berg <myon@debian.org>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
set -eu
binroot="/usr/lib/postgresql/"
#redhat# binroot="/usr/pgsql-"
if [ -z "${2:-}" ]; then
echo "Syntax: $0 /path/to/wal/%f %p" >&2
exit 1
fi
file="$1"
path="$2"
# sanity-check the first argument
waldir="$(dirname $file)"
if ! [ -d "$waldir" ]; then
echo "$0: $waldir is not a directory" >&2
exit 129
fi
if [ -f "$file.gz" ]; then
gunzip < "$file.gz" > "$path" || exit 129
elif [ -f "$file.lz4" ]; then
unlz4 < "$file.lz4" > "$path" || exit 129
elif [ -f "$file" ]; then
cp "$file" "$path" || exit 129
elif [ -f "$file.gz.partial" ] || [ -f "$file.lz4.partial" ]; then
if [ -s "$file.gz.partial" ]; then
gunzip < "$file.gz.partial" > "$path" || exit 129
elif [ -s "$file.lz4.partial" ]; then
unlz4 < "$file.lz4.partial" > "$path" || exit 129
else
# .gz.partial starts completely empty, gunzip doesn't like that
touch "$path" || exit 129
fi
# expand file to original size
version=$(cat PG_VERSION) || exit 129
wal_file_size=$(LC_ALL=C "$binroot$version/bin/pg_controldata" . | awk '/^Bytes per WAL segment:/ { print $5 }') || exit 129
[ "$wal_file_size" -gt 0 ] || exit 129
truncate --size="$wal_file_size" "$path" || exit 129
elif [ -f "$file.partial" ]; then
cp "$file.partial" "$path" || exit 129
else
# file not found, exit silently in order not to spam the server log with errors
exit 1
fi
exit 0
: <<=cut
=head1 NAME
pg_getwal - retrieve a WAL file from a pg_receivewal archive
=head1 SYNOPSIS
B<pg_getwal> I</path/to/wal/%f> I<%p>
=head1 DESCRIPTION
B<pg_getwal> retrieves and decompresses files from a WAL archive maintained by
B<pg_receivewal> and B<pg_backupcluster>. It is put into PostgreSQL's
B<restore_command> by B<pg_restorecluster>.
=head1 SEE ALSO
L<pg_restorecluster(1)>, L<pg_backupcluster(1)>.
=head1 AUTHOR
Christoph Berg L<E<lt>myon@debian.orgE<gt>>
=cut
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