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Asked: 2018-10-22 20:30:40 +0800 CST

VACUUM 没有减少报告的数据库大小？

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我有一个在 postgresql 中有一个非常大的表的数据库。

我知道缩小磁盘大小的唯一方法是VACUUM FULL，但我不能这样做，因为我没有足够的可用空间（这是 1TB 磁盘上的 920 GB 表，我买不起另一个 1TB SSD ATM）。

但是，我确实运行了VACUUM VERBOSE ANALYZE web_pages，它完成了，但是表大小（如 中所报告的psql）根本没有减小。

基本上，有没有办法在没有VACUUM FULL或完全转储/加载的情况下缩小表？我有转储/加载的空间，但在这一点上，我预计需要一周以上的时间。

真空输出：

webarchive=# VACUUM VERBOSE ANALYZE web_pages;
INFO:  vacuuming "public.web_pages"
INFO:  scanned index "ix_web_pages_distance_filtered" to remove 145580643 row versions
DETAIL:  CPU 4.46s/165.77u sec elapsed 324.63 sec
INFO:  scanned index "ix_web_pages_netloc" to remove 145580643 row versions
DETAIL:  CPU 40.65s/4686.88u sec elapsed 5387.13 sec
INFO:  scanned index "ix_web_pages_priority" to remove 145580643 row versions
DETAIL:  CPU 29.59s/1018.71u sec elapsed 1452.67 sec
INFO:  scanned index "ix_web_pages_state" to remove 145580643 row versions
DETAIL:  CPU 22.08s/303.12u sec elapsed 712.94 sec
INFO:  scanned index "ix_web_pages_url" to remove 145580643 row versions
DETAIL:  CPU 283.45s/673.39u sec elapsed 7583.39 sec
INFO:  scanned index "web_pages_pkey" to remove 145580643 row versions
DETAIL:  CPU 51.69s/90.19u sec elapsed 1461.37 sec
INFO:  scanned index "ix_web_pages_id" to remove 145580643 row versions
DETAIL:  CPU 63.13s/99.77u sec elapsed 1529.22 sec
INFO:  scanned index "web_pages_netloc_fetchtime_idx" to remove 145580643 row versions
DETAIL:  CPU 77.04s/5080.52u sec elapsed 6287.14 sec
INFO:  scanned index "id_web_pages_id_state" to remove 145580643 row versions
DETAIL:  CPU 64.52s/107.81u sec elapsed 1695.07 sec
INFO:  scanned index "web_pages_fetchtime_idx" to remove 145580643 row versions
DETAIL:  CPU 12.06s/99.66u sec elapsed 408.36 sec
INFO:  "web_pages": removed 145580643 row versions in 8584664 pages
DETAIL:  CPU 226.70s/140.17u sec elapsed 5019.28 sec
INFO:  index "ix_web_pages_distance_filtered" now contains 16007295 row versions in 814166 pages
DETAIL:  38738938 index row versions were removed.
570268 index pages have been deleted, 385915 are currently reusable.
CPU 0.00s/0.00u sec elapsed 0.02 sec.
INFO:  index "ix_web_pages_netloc" now contains 27370778 row versions in 3181634 pages
DETAIL:  67244989 index row versions were removed.
2669376 index pages have been deleted, 1876620 are currently reusable.
CPU 0.00s/0.00u sec elapsed 0.01 sec.
INFO:  index "ix_web_pages_priority" now contains 27370960 row versions in 2006220 pages
DETAIL:  67218177 index row versions were removed.
1056657 index pages have been deleted, 786603 are currently reusable.
CPU 0.01s/0.00u sec elapsed 0.03 sec.
INFO:  index "ix_web_pages_state" now contains 27370969 row versions in 1532024 pages
DETAIL:  67244989 index row versions were removed.
986826 index pages have been deleted, 700367 are currently reusable.
CPU 0.00s/0.00u sec elapsed 0.01 sec.
INFO:  index "ix_web_pages_url" now contains 27382514 row versions in 7555366 pages
DETAIL:  78562001 index row versions were removed.
4290425 index pages have been deleted, 225461 are currently reusable.
CPU 0.02s/0.00u sec elapsed 0.04 sec.
INFO:  index "web_pages_pkey" now contains 27401242 row versions in 2421605 pages
DETAIL:  78000787 index row versions were removed.
1068399 index pages have been deleted, 373558 are currently reusable.
CPU 0.00s/0.00u sec elapsed 0.01 sec.
INFO:  index "ix_web_pages_id" now contains 27411627 row versions in 2874706 pages
DETAIL:  82612172 index row versions were removed.
1290296 index pages have been deleted, 442226 are currently reusable.
CPU 0.00s/0.00u sec elapsed 0.01 sec.
INFO:  index "web_pages_netloc_fetchtime_idx" now contains 27556711 row versions in 4482440 pages
DETAIL:  80962513 index row versions were removed.
3373490 index pages have been deleted, 1873800 are currently reusable.
CPU 0.00s/0.00u sec elapsed 0.02 sec.
INFO:  index "id_web_pages_id_state" now contains 27558627 row versions in 3094617 pages
DETAIL:  81497647 index row versions were removed.
1735454 index pages have been deleted, 631419 are currently reusable.
CPU 0.00s/0.00u sec elapsed 0.01 sec.
INFO:  index "web_pages_fetchtime_idx" now contains 27559941 row versions in 656103 pages
DETAIL:  67710984 index row versions were removed.
228974 index pages have been deleted, 95938 are currently reusable.
CPU 0.00s/0.00u sec elapsed 0.00 sec.
INFO:  "web_pages": found 32297714 removable, 26459019 nonremovable row versions in 14298550 out of 14827067 pages
DETAIL:  1671 dead row versions cannot be removed yet.
There were 378926914 unused item pointers.
Skipped 0 pages due to buffer pins.
0 pages are entirely empty.
CPU 1149.21s/12598.17u sec elapsed 35893.00 sec.
INFO:  vacuuming "pg_toast.pg_toast_38269400"
INFO:  scanned index "pg_toast_38269400_index" to remove 178956680 row versions
DETAIL:  CPU 33.85s/139.43u sec elapsed 774.95 sec
INFO:  "pg_toast_38269400": removed 178956680 row versions in 47342563 pages
DETAIL:  CPU 1267.31s/752.22u sec elapsed 22404.29 sec
INFO:  scanned index "pg_toast_38269400_index" to remove 162873580 row versions
DETAIL:  CPU 20.65s/43.54u sec elapsed 216.38 sec
INFO:  "pg_toast_38269400": removed 162873580 row versions in 39900140 pages
DETAIL:  CPU 1085.52s/716.33u sec elapsed 13775.48 sec
INFO:  index "pg_toast_38269400_index" now contains 91453965 row versions in 1622691 pages
DETAIL:  341830260 index row versions were removed.
540140 index pages have been deleted, 1626 are currently reusable.
CPU 0.00s/0.00u sec elapsed 0.02 sec.
INFO:  "pg_toast_38269400": found 275718152 removable, 85526893 nonremovable row versions in 102611808 out of 104048880 pages
DETAIL:  1031 dead row versions cannot be removed yet.
There were 14286891 unused item pointers.
Skipped 0 pages due to buffer pins.
0 pages are entirely empty.
CPU 4786.16s/3240.77u sec elapsed 79646.66 sec.
INFO:  analyzing "public.web_pages"
INFO:  "web_pages": scanned 90000 of 14840002 pages, containing 166193 live rows and 1769 dead rows; 90000 rows in sample, 27403383 estimated total rows
VACUUM
webarchive=#

之前的尺寸报告：

webarchive=# \d+
                                List of relations
 Schema |                Name      |   Type   |    Owner    |    Size    | Description
--------+--------------------------+----------+-------------+------------+-------------
..... 
public | web_pages                | table    | webarchuser | 920 GB     |
.....

后：

webarchive=# \d+
                                List of relations
 Schema |                Name      |   Type   |    Owner    |    Size    | Description
--------+--------------------------+----------+-------------+------------+-------------
 ........
 public | web_pages                | table    | webarchuser | 920 GB     |
 ........

我意识到这里的“正确”解决方案是更大的磁盘，但这是一个爱好项目（尽管规模非常大），我只是没有钱购买更大的 SSD 存储。

postgresql maintenance

3 个回答

  1. Best Answer

    有没有办法缩小报告的大小（例如你在 psql 中使用 \d+ 得到的）？我假设 \d+ 报告了使用的元组的大小，而不仅仅是磁盘原语

    不，\d+ 报告磁盘上的大小。如果您想知道有多少空间可用于内部重用，请参阅核心pg_freespacemap扩展。如果这显示了很多内部空间，并且您想实际尝试缩小表并将空间返回给操作系统，请尝试非核心pg_repack扩展。但是如果转储和重新加载需要一周时间，我怀疑 pg_repack 会迅速完成。

    • 3

  2. VACUUM释放表内的空间，如果你想减少你必须使用的表的磁盘大小VACUUM FULL

    • 1

  3. 如果表中的最后一条记录已死，vacuum 将修剪表。因此，随着足够频繁的真空和足够的流失（记录重写），表格将逐渐缩小。

    手册：https ://www.postgresql.org/docs/current/static/routine-vacuuming.html

    VACUUM 的标准形式删除表和索引中的死行版本，并标记可用空间以供将来重用。但是，它不会将空间返回给操作系统，除非在特殊情况下，表末尾的一个或多个页面变得完全空闲并且可以轻松获得排他表锁。

    • 0

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