pg_upgrade does not support a table 2 in the original database to inherit from table 1 (field F_Test1 is not empty), and then table 2 modifies F by itself_ Test1 is nullable
标题：pg_upgrade 不支持原始数据库里的某个表2从表1继承（字段F_Test1非空），表2然后自己修改F_Test1为可空
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[Emphasis] [Test version PostgreSQL 15.2] pg_ Upgrade internal call pg_ The dump command line uses the -- binary upgrade parameter
Problem description:
If a table 2 in the original database inherits from table 1 (field F_Test1 is not empty), table 2 then modifies F_ Test1 is nullable, use pg_ Dump -- binary-upgrade After backup.
pg_ When restoring, after creating Table 1 and Table 2 respectively, execute something like ALTER TABLE "T1" INHERIT "T2"; Error will be reported.
1) [Test succeeded] After the test, do not use pg_ The -- binary-upgrade parameter of dump uses the conventional parameter, after backup;
Use pg_ Whether restore can successfully restore the database using the - disable-triggers parameter or not.
2）pg_ The dump -- binary upgrade parameter is the same as the general SQL support. Create an inheritance relationship between two tables with the following restrictions:
DROP TABLE "T1";
CREATE TABLE IF NOT EXISTS "T1"(
"F_Test" text NOT NULL, -- inherited field
"F_Other" text -- other fields
);
DROP TABLE "T2";
CREATE TABLE IF NOT EXISTS "T2"(
"F_Test" text -- Inherit field. [Null field]
);
ALTER TABLE "T1" INHERIT "T2"; -- Set inheritance relationship. [Implementation succeeded]. When T1. F_ When Test is not empty, T2. F_ Whether the test uses NOT NULL is successful.
ALTER TABLE "T1" NO INHERIT "T2"; -- Cancel inheritance
ALTER TABLE "T2" ALTER COLUMN "F_Test" SET NOT NULL; -- T2.F_ Test field is set to non-empty
ALTER TABLE "T1" ALTER COLUMN "F_Test" DROP NOT NULL; -- T1.F_ The Test field is set to nullable
ALTER TABLE "T1" INHERIT "T2"; -- [Execution failed]. When T2. F_ When Test is not empty, T1. F_ Test must be NOT NULL or the execution fails.
1> When creating an inheritance relationship between two tables, the parent table is a non-empty field, and the corresponding field of the child table must be a non-empty field, otherwise the inheritance relationship cannot be established.
If the field of the child table is non-empty, the inheritance relationship can be established whether the corresponding field of the parent table is non-empty.
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【重点】【测试版本PostgreSQL 15.2】pg_upgrade内部调用pg_dump命令行使用--binary-upgrade参数
问题描述：
如果原始数据库里的某个表2从表1继承（字段F_Test1非空），表2然后自己修改F_Test1为可空，使用pg_dump --binary-upgrade备份后。
pg_restore还原时，在分别创建表1、表2后，执行类似ALTER TABLE "T1" INHERIT "T2";会报错。
1）【测试成功】经过测试，此情况，不要使用pg_dump的--binary-upgrade参数，而是使用常规的参数，备份后；
使用pg_restore是否使用-disable-triggers参数都能成功还原数据库。
2）pg_dump--binary-upgrade参数与常规支持SQL一样。新建两个表之间的继承关系，有如下条件限制：
DROP TABLE "T1";
CREATE TABLE IF NOT EXISTS "T1"(
"F_Test" text NOT NULL, --继承字段
"F_Other" text --其他字段
);
DROP TABLE "T2";
CREATE TABLE IF NOT EXISTS "T2"(
"F_Test" text --继承字段。【可空字段】
);
ALTER TABLE "T1" INHERIT "T2"; --设置继承关系。【执行成功】。当T1.F_Test非空时，T2.F_Test是否使用NOT NULL都是执行成功。
ALTER TABLE "T1" NO INHERIT "T2"; --取消继承
ALTER TABLE "T2" ALTER COLUMN "F_Test" SET NOT NULL; --T2.F_Test字段设置为非空
ALTER TABLE "T1" ALTER COLUMN "F_Test" DROP NOT NULL; --T1.F_Test字段设置为可空
ALTER TABLE "T1" INHERIT "T2"; --【执行失败】。当T2.F_Test非空时，T1.F_Test必须为NOT NULL否则执行失败。
1> 新建两个表之间的继承关系时，父表为非空字段，子表则对应字段必须为非空字段，否则无法建立继承关系。
如果子表的字段为非空，父表的对应字段是否为非空都可以建立继承关系。
