为啥用户表的大小远小于 PostgreSQL 数据库中其他对象的大小
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【中文标题】为啥用户表的大小远小于 PostgreSQL 数据库中其他对象的大小【英文标题】：Why the size of user tables is much less that the size of other objects in a PostgreSQL database为什么用户表的大小远小于 PostgreSQL 数据库中其他对象的大小 【发布时间】：2016-10-10 16:07:52 【问题描述】：我需要帮助来了解我的数据库的大小。我想这个问题很友好 对数据库专业人士来说很简单。我不是专业人士，但我想了解。我用 PostgreSQL。还有一个细节。我的应用程序是用 java 编写并部署在 PWS 中 试用帐户中的云。最大可用数据库大小为 20MB。这足以 测试和开发。现在经过几个月的开发，我的数据库 大小超过了限制，变成了大约 25MB。但从用户的 透视（实际上是从我的角度来看）我的数据大小要小得多 超过 25MB。所以我想知道是什么占用了空间。
所以，这里是数据库结构：
# \d
List of relations
Schema | Name | Type
--------+--------------------+----------
public | hibernate_sequence | sequence
public | post | table
public | site | table
public | user_account | table
public | user_authority | table
public | userconnection | table
(6 rows)
# \d post
Table "public.post"
Column | Type | Modifiers
----------------+-----------------------------+-----------
id | bigint | not null
author | character varying(255) |
content | text | not null
creation_time | timestamp without time zone | not null
tags | character varying(255) |
title | text | not null
url | character varying(255) | not null
site_id | bigint | not null
published_date | timestamp without time zone | not null
uri | character varying(255) | not null
Indexes:
"post_pkey" PRIMARY KEY, btree (id)
Foreign-key constraints:
"fkadd3gkkmgwsi1dy825qkfd62e" FOREIGN KEY (site_id) REFERENCES site(id)
# \d site
Table "public.site"
Column | Type | Modifiers
--------------+-----------------------------+-----------
id | bigint | not null
last_visited | timestamp without time zone |
title | text |
url | character varying(255) | not null
description | text |
Indexes:
"site_pkey" PRIMARY KEY, btree (id)
Referenced by:
TABLE "post" CONSTRAINT "fkadd3gkkmgwsi1dy825qkfd62e" FOREIGN KEY (site_id) REFERENCES site(id)
# \d user_account
Table "public.user_account"
Column | Type | Modifiers
-------------------+-----------------------------+-----------
id | bigint | not null
email | character varying(255) | not null
first_name | character varying(255) |
last_name | character varying(255) |
last_request_time | timestamp without time zone | not null
password | character varying(255) | not null
registration_time | timestamp without time zone | not null
Indexes:
"user_account_pkey" PRIMARY KEY, btree (id)
"uk_hl02wv5hym99ys465woijmfib" UNIQUE CONSTRAINT, btree (email)
Referenced by:
TABLE "user_authority" CONSTRAINT "fkn48a3n0mb8d8njshjf75kgsv" FOREIGN KEY (user_id) REFERENCES user_account(id)
# \d userconnection
Table "public.userconnection"
Column | Type | Modifiers
----------------+------------------------+-----------
userid | character varying(255) | not null
providerid | character varying(255) | not null
provideruserid | character varying(255) | not null
rank | integer | not null
displayname | character varying(255) |
profileurl | character varying(512) |
imageurl | character varying(512) |
accesstoken | character varying(512) | not null
secret | character varying(512) |
refreshtoken | character varying(512) |
expiretime | bigint |
Indexes:
"userconnection_pkey" PRIMARY KEY, btree (userid, providerid, provideruserid)
"userconnectionrank" UNIQUE, btree (userid, providerid, rank)
# \d user_authority
Table "public.user_authority"
Column | Type | Modifiers
-----------+------------------------+-----------
authority | character varying(255) | not null
user_id | bigint | not null
Indexes:
"user_authority_pkey" PRIMARY KEY, btree (user_id, authority)
Foreign-key constraints:
"fkn48a3n0mb8d8njshjf75kgsv" FOREIGN KEY (user_id) REFERENCES user_account(id)
Here's the databases's size:
select pg_database_size('rodiahug');
pg_database_size
25714860
这是我用来确定表大小的查询：
SELECT
relname as "Table",
pg_size_pretty(pg_total_relation_size(relid)) As "Size",
pg_size_pretty(pg_total_relation_size(relid) - pg_relation_size(relid)) as "External Size"
FROM pg_catalog.pg_statio_user_tables ORDER BY pg_total_relation_size(relid) DESC;
Table Size External Size
site 64 kB 56 kB
user_account 48 kB 40 kB
post 48 kB 24 kB
userconnection 48 kB 40 kB
user_authority 24 kB 16 kB
正如我们所见，添加所有大小远小于 24MB。
天真的谷歌搜索对象大小的查询给出了查询：
SELECT
relname AS objectname,
relkind AS objecttype,
reltuples AS "#entries", pg_size_pretty(relpages::bigint*8*1024) AS size
FROM pg_class
WHERE relpages >= 1 AND reltuples > 0
ORDER BY relpages DESC;
objectname objecttype #entries size
pg_largeobject r 129767.0 6152 kB
pg_largeobject_metadata r 131790.0 5704 kB
pg_shdepend_depender_index i 71390.0 4368 kB
pg_shdepend r 71390.0 4296 kB
pg_largeobject_metadata_oid_index i 131790.0 2912 kB
pg_largeobject_loid_pn_index i 129767.0 2872 kB
pg_shdepend_reference_index i 71390.0 2576 kB
pg_database r 5048.0 1496 kB
pg_proc r 3473.0 712 kB
pg_depend r 11312.0 672 kB
pg_authid r 2921.0 448 kB
pg_attribute r 2573.0 376 kB
pg_depend_depender_index i 11312.0 368 kB
pg_depend_reference_index i 11312.0 368 kB
pg_description r 3876.0 272 kB
pg_proc_proname_args_nsp_index i 3473.0 264 kB
pg_database_datname_index i 4214.0 176 kB
pg_authid_rolname_index i 2901.0 168 kB
pg_statistic r 422.0 144 kB
pg_operator r 907.0 136 kB
pg_attribute_relid_attnam_index i 2573.0 136 kB
pg_database_oid_index i 4214.0 136 kB
pg_description_o_c_o_index i 3876.0 136 kB
pg_rewrite r 115.0 96 kB
pg_proc_oid_index i 3473.0 96 kB
pg_attribute_relid_attnum_index i 2573.0 96 kB
pg_authid_oid_index i 2901.0 88 kB
pg_type r 416.0 80 kB
pg_collation r 303.0 80 kB
pg_amop r 1025.0 72 kB
pg_class r 337.0 72 kB
pg_amproc r 904.0 56 kB
pg_class_relname_nsp_index i 337.0 56 kB
pg_amproc_fam_proc_index i 904.0 48 kB
pg_operator_oprname_l_r_n_index i 907.0 48 kB
pg_amop_opr_fam_index i 1025.0 48 kB
pg_type_typname_nsp_index i 416.0 48 kB
pg_amop_fam_strat_index i 1025.0 48 kB
pg_class_tblspc_relfilenode_index i 337.0 40 kB
pg_amop_oid_index i 1025.0 40 kB
pg_operator_oid_index i 907.0 40 kB
pg_amproc_oid_index i 904.0 40 kB
pg_class_oid_index i 337.0 40 kB
pg_ts_config_map_index i 304.0 32 kB
pg_statistic_relid_att_inh_index i 422.0 32 kB
pg_collation_name_enc_nsp_index i 303.0 32 kB
pg_type_oid_index i 416.0 32 kB
pg_opclass_am_name_nsp_index i 219.0 32 kB
pg_opclass r 219.0 32 kB
pg_conversion r 132.0 24 kB
post r 67.0 24 kB
pg_toast_2619 t 15.0 24 kB
pg_index r 131.0 24 kB
pg_opfamily r 172.0 24 kB
pg_rewrite_oid_index i 115.0 16 kB
pg_rewrite_rel_rulename_index i 115.0 16 kB
pg_trigger_tgconstraint_index i 8.0 16 kB
pg_trigger_tgrelid_tgname_index i 8.0 16 kB
pg_namespace_nspname_index i 6.0 16 kB
pg_namespace_oid_index i 6.0 16 kB
pg_ts_config_cfgname_index i 16.0 16 kB
pg_ts_config_oid_index i 16.0 16 kB
pg_ts_dict_dictname_index i 19.0 16 kB
pg_ts_dict_oid_index i 19.0 16 kB
pg_ts_parser_prsname_index i 1.0 16 kB
pg_ts_parser_oid_index i 1.0 16 kB
pg_ts_template_tmplname_index i 8.0 16 kB
pg_ts_template_oid_index i 8.0 16 kB
pg_foreign_data_wrapper_oid_index i 1.0 16 kB
pg_foreign_data_wrapper_name_index i 1.0 16 kB
pg_extension_oid_index i 24.0 16 kB
pg_range_rngtypid_index i 6.0 16 kB
site_pkey i 3.0 16 kB
userconnectionrank i 4.0 16 kB
userconnection_pkey i 4.0 16 kB
pg_index_indexrelid_index i 131.0 16 kB
pg_am_oid_index i 6.0 16 kB
pg_aggregate_fnoid_index i 140.0 16 kB
pg_index_indrelid_index i 131.0 16 kB
pg_cast_oid_index i 224.0 16 kB
pg_cast_source_target_index i 224.0 16 kB
pg_conversion_default_index i 132.0 16 kB
pg_conversion_name_nsp_index i 132.0 16 kB
pg_conversion_oid_index i 132.0 16 kB
pg_constraint_contypid_index i 13.0 16 kB
pg_constraint_conrelid_index i 13.0 16 kB
pg_collation_oid_index i 303.0 16 kB
pg_pltemplate_name_index i 8.0 16 kB
pg_constraint_conname_nsp_index i 13.0 16 kB
pg_shdescription_o_c_index i 1.0 16 kB
pg_tablespace_oid_index i 2.0 16 kB
pg_tablespace_spcname_index i 2.0 16 kB
pg_toast_2619_index i 15.0 16 kB
user_authority_pkey i 5.0 16 kB
pg_opfamily_am_name_nsp_index i 172.0 16 kB
pg_opfamily_oid_index i 172.0 16 kB
pg_opclass_oid_index i 219.0 16 kB
pg_language_name_index i 5.0 16 kB
pg_language_oid_index i 5.0 16 kB
user_account_pkey i 3.0 16 kB
uk_hl02wv5hym99ys465woijmfib i 3.0 16 kB
pg_cast r 224.0 16 kB
pg_ts_config_map r 304.0 16 kB
pg_extension_name_index i 24.0 16 kB
post_pkey i 67.0 16 kB
pg_constraint_oid_index i 13.0 16 kB
pg_aggregate r 140.0 16 kB
pg_trigger_oid_index i 8.0 16 kB
pg_am_name_index i 6.0 16 kB
pg_ts_config r 16.0 8192 bytes
pg_am r 6.0 8192 bytes
pg_ts_dict r 19.0 8192 bytes
pg_ts_parser r 1.0 8192 bytes
pg_ts_template r 8.0 8192 bytes
pg_extension r 24.0 8192 bytes
pg_foreign_data_wrapper r 1.0 8192 bytes
user_account r 3.0 8192 bytes
pg_range r 6.0 8192 bytes
pg_constraint r 13.0 8192 bytes
pg_tablespace r 2.0 8192 bytes
user_authority r 5.0 8192 bytes
pg_shdescription r 1.0 8192 bytes
site r 3.0 8192 bytes
pg_trigger r 8.0 8192 bytes
userconnection r 4.0 8192 bytes
pg_language r 5.0 8192 bytes
pg_namespace r 6.0 8192 bytes
pg_pltemplate r 8.0 8192 bytes
hibernate_sequence S 1.0 8192 bytes
在这里，我想了解为什么这些物体占用空间更多 比我的用户表？ 例如，这些：
pg_largeobject r 129767.0 6152 kB
pg_largeobject_metadata r 131790.0 5704 kB
pg_shdepend_depender_index i 71390.0 4368 kB
pg_shdepend r 71390.0 4296 kB
pg_largeobject_metadata_oid_index i 131790.0 2912 kB
pg_largeobject_loid_pn_index i 129767.0 2872 kB
pg_shdepend_reference_index i 71390.0 2576 kB
pg_database r 5048.0 1496 kB
这正常吗？我应该/我可以做些什么吗？
【问题讨论】：
【参考方案1】：您最后一次吸尘是什么时候？它可以轻松减小开发数据库的大小。 此外，索引通常比它们索引的数据大，原因是数据对齐是为了速度，而不是空间效率。
PG 还有一组关于您的数据库的元数据和其他“幕后”表来跟踪事物。它跟踪有关您的数据的统计信息，例如最小值和最大值，以及有关您的数据和 postgres 的元数据/维护表中的特定经常出现的值的统计信息。
当您删除数据时，数据并没有真正从数据库中“删除”——因此，建议使用“真空满”。 Vacuum Full 将锁定您的表并重建它们，合并可用空间并消除以前删除的记录中的空间。像 pg_largeobject 这样的表实际上存储了来自数据库中“大”记录的数据，而且由于以前存储的数据现在被删除了，所以数据也可能很大。
我会做一个真空充满，看看你会得到什么结果。
【讨论】：
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