postgresql依赖跟踪 cascade和restrict选项
作者：互联网
weather表的外键为cities的主键city字段，如下为表结构
mydb=# \d weather
Table "public.weather"
Column | Type | Collation | Nullable | Default
---------+-----------------------+-----------+----------+---------
city | character varying(80) | | |
temp_lo | integer | | |
temp_hi | integer | | |
prcp | real | | |
date | date | | |
Foreign-key constraints:
"weather_city_fkey" FOREIGN KEY (city) REFERENCES cities(city)
mydb=# \d cities
Table "public.cities"
Column | Type | Collation | Nullable | Default
----------+-----------------------+-----------+----------+---------
city | character varying(80) | | not null |
location | point | | |
Indexes:
"cities_pkey" PRIMARY KEY, btree (city)
Referenced by:
TABLE "weather" CONSTRAINT "weather_city_fkey" FOREIGN KEY (city) REFERENCES cities(city)
删除cities表，报错无法删除，有依赖该表的对象
mydb=# drop table cities ;
2022-06-23 09:38:11.501 CST [7191] ERROR: cannot drop table cities because other objects depend on it
2022-06-23 09:38:11.501 CST [7191] DETAIL: constraint weather_city_fkey on table weather depends on table cities
2022-06-23 09:38:11.501 CST [7191] HINT: Use DROP ... CASCADE to drop the dependent objects too.
2022-06-23 09:38:11.501 CST [7191] STATEMENT: drop table cities ;
ERROR: cannot drop table cities because other objects depend on it
DETAIL: constraint weather_city_fkey on table weather depends on table cities
HINT: Use DROP ... CASCADE to drop the dependent objects too.
mydb=#
mydb=#
使用cascade选项删除
mydb=# drop table cities CASCADE;
NOTICE: drop cascades to constraint weather_city_fkey on table weather
DROP TABLE
mydb=# \d
List of relations
Schema | Name | Type | Owner
--------+----------+-------+----------
public | accounts | table | postgres
public | product | table | postgres
public | rsl | table | user01
public | weather | table | postgres
(4 rows)
mydb=#
mydb=#
cities表已经删除weather表还存在，但是外键约束已经被级联删除
mydb=# \d weather
Table "public.weather"
Column | Type | Collation | Nullable | Default
---------+-----------------------+-----------+----------+---------
city | character varying(80) | | |
temp_lo | integer | | |
temp_hi | integer | | |
prcp | real | | |
date | date | | |
使用restrict选项，其实就是默认的drop table table_name的默认行为，
mydb=# create table city (city varchar(80) primary key,location point);
CREATE TABLE
mydb=# \d city
Table "public.city"
Column | Type | Collation | Nullable | Default
----------+-----------------------+-----------+----------+---------
city | character varying(80) | | not null |
location | point | | |
Indexes:
"city_pkey" PRIMARY KEY, btree (city)
mydb=# alter table city rename to cities;
ALTER TABLE
mydb=#
mydb=# \d cities
Table "public.cities"
Column | Type | Collation | Nullable | Default
----------+-----------------------+-----------+----------+---------
city | character varying(80) | | not null |
location | point | | |
Indexes:
"city_pkey" PRIMARY KEY, btree (city)
mydb=# \d
List of relations
Schema | Name | Type | Owner
--------+----------+-------+----------
public | accounts | table | postgres
public | cities | table | postgres
public | product | table | postgres
public | rsl | table | user01
public | weather | table | postgres
(5 rows)
mydb=# ALTER TABLE weather ADD CONSTRAINT weather_city_fkey FOREIGN KEY (city) REFERENCES cities (city);
ALTER TABLE
mydb=#
mydb=#
mydb=# \d weather
Table "public.weather"
Column | Type | Collation | Nullable | Default
---------+-----------------------+-----------+----------+---------
city | character varying(80) | | |
temp_lo | integer | | |
temp_hi | integer | | |
prcp | real | | |
date | date | | |
Foreign-key constraints:
"weather_city_fkey" FOREIGN KEY (city) REFERENCES cities(city)
mydb=#
mydb=#
mydb=#
mydb=#
mydb=# drop table cities restrict ;
2022-06-23 09:44:33.279 CST [7191] ERROR: cannot drop table cities because other objects depend on it
2022-06-23 09:44:33.279 CST [7191] DETAIL: constraint weather_city_fkey on table weather depends on table cities
2022-06-23 09:44:33.279 CST [7191] HINT: Use DROP ... CASCADE to drop the dependent objects too.
2022-06-23 09:44:33.279 CST [7191] STATEMENT: drop table cities restrict ;
ERROR: cannot drop table cities because other objects depend on it
DETAIL: constraint weather_city_fkey on table weather depends on table cities
HINT: Use DROP ... CASCADE to drop the dependent objects too.
对于用户定义的函数，PostgreSQL会追踪与函数外部可见性质相关的依赖性，例如它的参数和结果类型，但不追踪检查函数体才能知道的依赖性。例如，考虑这种情况：
CREATE TYPE rainbow AS ENUM ('red', 'orange', 'yellow','green', 'blue', 'purple');
CREATE TABLE my_colors (color rainbow, note text);
CREATE FUNCTION get_color_note (rainbow) RETURNS text AS
'SELECT note FROM my_colors WHERE color = $1'
LANGUAGE SQL;
PostgreSQL将会注意到get_color_note函数依赖于rainbow类型：删掉该类型会强制删除该函数，因为该函数的参数类型就无法定义了。但是PostgreSQL不会认为get_color_note依赖于my_colors表，因此即使该表被删除也不会删除这个函数。虽然这种方法有缺点，但是也有好处。如果该表丢失，这个函数在某种程度上仍然是有效的，但是执行它会导致错误。创建一个同名的新表将允许该函数重新有效。
实例
创建测试数据
mydb=# CREATE TYPE rainbow AS ENUM ('red', 'orange', 'yellow','green', 'blue', 'purple');
CREATE TYPE
mydb=# CREATE TABLE my_colors (color rainbow, note text);
CREATE TABLE
mydb=# CREATE FUNCTION get_color_note (rainbow) RETURNS text AS 'SELECT note FROM my_colors WHERE color = $1' LANGUAGE SQL;
CREATE FUNCTION
mydb=#
mydb=#
mydb=#
查看函数定义
mydb=# \df get_c
get_color_note get_current_ts_config
mydb=# \df get_color_note
List of functions
Schema | Name | Result data type | Argument data types | Type
--------+----------------+------------------+---------------------+--------
public | get_color_note | text | rainbow | normal
(1 row)
调用函数测试
mydb=# select get_color_note('red');
get_color_note
----------------
(1 row)
mydb=# select get_color_note('orange');
get_color_note
----------------
(1 row)
删除表
mydb=# drop table my_colors
mydb-# ;
DROP TABLE
删除表后，该函数还是存在的，重建表之后还是可以调用该函数
mydb=# select get_color_note('orange');
2022-06-23 09:54:27.797 CST [7191] ERROR: relation "my_colors" does not exist at character 18
2022-06-23 09:54:27.797 CST [7191] QUERY: SELECT note FROM my_colors WHERE color = $1
2022-06-23 09:54:27.797 CST [7191] CONTEXT: SQL function "get_color_note" during inlining
2022-06-23 09:54:27.797 CST [7191] STATEMENT: select get_color_note('orange');
ERROR: relation "my_colors" does not exist
LINE 1: SELECT note FROM my_colors WHERE color = $1
^
QUERY: SELECT note FROM my_colors WHERE color = $1
CONTEXT: SQL function "get_color_note" during inlining
mydb=#
mydb=#
mydb=#
mydb=# CREATE TABLE my_colors (color rainbow, note text);
CREATE TABLE
mydb=#
mydb=#
mydb=# select get_color_note('orange');
get_color_note
----------------
(1 row)
删除类型，该类型rainbow是函数的参数，所以将该参数删除后，函数也会被删除
mydb=# drop type rainbow;
2022-06-23 09:54:54.620 CST [7191] ERROR: cannot drop type rainbow because other objects depend on it
2022-06-23 09:54:54.620 CST [7191] DETAIL: function get_color_note(rainbow) depends on type rainbow
table my_colors column color depends on type rainbow
2022-06-23 09:54:54.620 CST [7191] HINT: Use DROP ... CASCADE to drop the dependent objects too.
2022-06-23 09:54:54.620 CST [7191] STATEMENT: drop type rainbow;
ERROR: cannot drop type rainbow because other objects depend on it
DETAIL: function get_color_note(rainbow) depends on type rainbow
table my_colors column color depends on type rainbow
HINT: Use DROP ... CASCADE to drop the dependent objects too.
mydb=# drop type rainbow cascade ;
NOTICE: drop cascades to 2 other objects
DETAIL: drop cascades to function get_color_note(rainbow)
drop cascades to table my_colors column color
DROP TYPE
mydb=#
mydb=# \df get_clo
mydb=# \df get_clo
mydb=# \df get_clo
mydb=# \df get_color_note;
List of functions
Schema | Name | Result data type | Argument data types | Type
--------+------+------------------+---------------------+------
(0 rows)
mydb=#
参考pg官方文档：http://postgres.cn/docs/14/ddl-depend.html
标签：city,note,postgresql,color,restrict,cascade,table,cities,mydb 来源： https://www.cnblogs.com/nanblog/p/16404112.html