PostgreSQL16中pg_dump的LZ4和ZSTD压缩

Expand pg_dump's compression streaming and file APIs to 
support the lz4 algorithm. The newly added compress_lz4.{c,h} 
files cover all the functionality of the aforementioned APIs. 
Minor changes were necessary in various pg_backup_* files, 
where code for the 'lz4' file suffix has been added, 
as well as pg_dump's compression option parsing.
Author: Georgios Kokolatos
Reviewed-by: Michael Paquier, Rachel Heaton, Justin Pryzby, 
Shi Yu, Tomas Vondra
Discussion: 
https://postgr.es/m/faUNEOpts9vunEaLnmxmG-DldLSg_ql137OC3JYDmgrOMHm1RvvWY2IdBkv_CRxm5spCCb_OmKNk2T03TMm0fBEWveFF9wA1WizPuAgB7Ss%3D%40protonmail.com

Allow pg_dump to use the zstd compression, 
in addition to gzip/lz4. Bulk of the new compression method 
is implemented in compress_zstd.{c,h},covering the pg_dump 
compression APIs. The rest of the patch adds test and makes
 various places aware of the new compression method.
The zstd library (which this patch relies on) supports 
multithreaded compression since version 1.5. We however 
disallow that feature for now, as it might interfere with 
parallel backups on platforms that rely on threads 
(e.g. Windows). This can be improved / relaxed in the future.
This also fixes a minor issue in 
InitDiscoverCompressFileHandle(), which was not updated to 
check if the file already has the .lz4 extension.
Adding zstd compression was originally proposed in 2020 
(see the second thread), but then was reworked to use the 
new compression API introduced in e9960732a9. I've considered 
both threads when compiling the list of reviewers.
Author: Justin Pryzby
Reviewed-by: Tomas Vondra, Jacob Champion, Andreas Karlsson
Discussion: https://postgr.es/m/20230224191840.GD1653@telsasoft.com
Discussion: https://postgr.es/m/20201221194924.GI30237@telsasoft.com

~$ pg_dump --version
pg_dump (PostgreSQL) 16devel
~$ pgbench --initialize --scale=100
dropping old tables...
NOTICE: table "pgbench_accounts" does not exist, skipping
NOTICE: table "pgbench_branches" does not exist, skipping
NOTICE: table "pgbench_history" does not exist, skipping
NOTICE: table "pgbench_tellers" does not exist, skipping
creating tables...
generating data (client-side)...
10000000 of 10000000 tuples (100%) done (elapsed 39.52 s, remaining 0.00 s)
vacuuming...
creating primary keys...
done in 49.65 s (drop tables 0.00 s, create tables 0.08 s, client-side generate 39.96 s, vacuum 0.29 s, primary keys 9.32 s).
~$ psql --command="select pg_size_pretty(pg_database_size('postgres'))"
pg_size_pretty 
----------------
1503 MB
(1 row)
~$ time pg_dump --format=custom --compress=lz4:9 > dump.lz4
real 0m10.507s
user 0m9.901s
sys 0m0.436s
~$ time pg_dump --format=custom --compress=zstd:9 > dump.zstd
real 0m8.794s
user 0m8.393s
sys 0m0.364s
~$ time pg_dump --format=custom --compress=gzip:9 > dump.gz
real 0m14.245s
user 0m13.064s
sys 0m0.978s
~$ time pg_dump --format=custom --compress=lz4 > dump_default.lz4
real 0m6.809s
user 0m1.666s
sys 0m1.125s
~$ time pg_dump --format=custom --compress=zstd > dump_default.zstd
real 0m7.534s
user 0m2.428s
sys 0m0.892s
~$ time pg_dump --format=custom --compress=gzip > dump_default.gz
real 0m11.564s
user 0m10.661s
sys 0m0.525s
~$ time pg_dump --format=custom --compress=lz4:3 > dump_3.lz4
real 0m8.497s
user 0m7.856s
sys 0m0.507s
~$ time pg_dump --format=custom --compress=zstd:3 > dump_3.zstd
real 0m5.129s
user 0m2.228s
sys 0m0.726s
~$ time pg_dump --format=custom --compress=gzip:3 > dump_3.gz
real 0m4.468s
user 0m3.654s
sys 0m0.504s
~$ ls -l --block-size=M
total 250M
-rw-rw-r-- 1 postgres postgres 28M Apr 18 13:58 dump_3.gz
-rw-rw-r-- 1 postgres postgres 48M Apr 18 13:57 dump_3.lz4
-rw-rw-r-- 1 postgres postgres 8M Apr 18 13:58 dump_3.zstd
-rw-rw-r-- 1 postgres postgres 27M Apr 18 13:57 dump_default.gz
-rw-rw-r-- 1 postgres postgres 50M Apr 18 13:56 dump_default.lz4
-rw-rw-r-- 1 postgres postgres 8M Apr 18 13:57 dump_default.zstd
-rw-rw-r-- 1 postgres postgres 27M Apr 18 13:56 dump.gz
-rw-rw-r-- 1 postgres postgres 48M Apr 18 13:55 dump.lz4
-rw-rw-r-- 1 postgres postgres 8M Apr 18 13:56 dump.zstd