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Switch pg_dump to use compression specifications

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Compression specifications are currently used by pg_basebackup and
pg_receivewal, and are able to let the user control in an extended way
the method and level of compression used.  As an effect of this commit,
pg_dump's -Z/--compress is now able to use more than just an integer, as
of the grammar "method[:detail]".

The method can be either "none" or "gzip", and can optionally take a
detail string.  If the detail string is only an integer, it defines the
compression level.  A comma-separated list of keywords can also be used
method allows for more options, the only keyword supported now is
"level".

The change is backward-compatible, hence specifying only an integer
leads to no compression for a level of 0 and gzip compression when the
level is greater than 0.

Most of the code changes are straight-forward, as pg_dump was relying on
an integer tracking the compression level to check for gzip or no
compression.  These are changed to use a compression specification and
the algorithm stored in it.

As of this change, note that the dump format is not bumped because there
is no need yet to track the compression algorithm in the TOC entries.
Hence, we still rely on the compression level to make the difference
when reading them.  This will be mandatory once a new compression method
is added, though.

In order to keep the code simpler when parsing the compression
specification, the code is changed so as pg_dump now fails hard when
using gzip on -Z/--compress without its support compiled, rather than
enforcing no compression without the user knowing about it except
through a warning.  Like before this commit, archive and custom formats
are compressed by default when the code is compiled with gzip, and left
uncompressed without gzip.

Author: Georgios Kokolatos
Reviewed-by: Michael Paquier
Discussion: https://postgr.es/m/O4mutIrCES8ZhlXJiMvzsivT7ztAMja2lkdL1LJx6O5f22I2W8PBIeLKz7mDLwxHoibcnRAYJXm1pH4tyUNC4a8eDzLn22a6Pb1S74Niexg=@pm.me
This commit is contained in:
Michael Paquier
2022-12-02 10:45:02 +09:00
parent edf12e7bbd
commit 5e73a60488
14 changed files with 260 additions and 160 deletions
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38
doc/src/sgml/ref/pg_dump.sgml
View File

@ -644,17 +644,39 @@ PostgreSQL documentation
</varlistentry>
<varlistentry>
<term><option>-Z <replaceable class="parameter">0..9</replaceable></option></term>
<term><option>--compress=<replaceable class="parameter">0..9</replaceable></option></term>
<term><option>-Z <replaceable class="parameter">level</replaceable></option></term>
<term><option>-Z <replaceable class="parameter">method</replaceable></option>[:<replaceable>detail</replaceable>]</term>
<term><option>--compress=<replaceable class="parameter">level</replaceable></option></term>
<term><option>--compress=<replaceable class="parameter">method</replaceable></option>[:<replaceable>detail</replaceable>]</term>
<listitem>
<para>
Specify the compression level to use. Zero means no compression.
Specify the compression method and/or the compression level to use.
The compression method can be set to <literal>gzip</literal> or
<literal>none</literal> for no compression.
A compression detail string can optionally be specified. If the
detail string is an integer, it specifies the compression level.
Otherwise, it should be a comma-separated list of items, each of the
form <literal>keyword</literal> or <literal>keyword=value</literal>.
Currently, the only supported keyword is <literal>level</literal>.
</para>
<para>
If no compression level is specified, the default compression
level will be used. If only a level is specified without mentioning
an algorithm, <literal>gzip</literal> compression will be used if
the level is greater than <literal>0</literal>, and no compression
will be used if the level is <literal>0</literal>.
</para>
<para>
For the custom and directory archive formats, this specifies compression of
individual table-data segments, and the default is to compress
at a moderate level.
For plain text output, setting a nonzero compression level causes
the entire output file to be compressed, as though it had been
fed through <application>gzip</application>; but the default is not to compress.
individual table-data segments, and the default is to compress using
<literal>gzip</literal> at a moderate level. For plain text output,
setting a nonzero compression level causes the entire output file to be compressed,
as though it had been fed through <application>gzip</application>; but the default
is not to compress.
</para>
<para>
The tar archive format currently does not support compression at all.
</para>
</listitem>