国庆之际，PostgreSQL全球开发组发布了15 RC1，文章链接如下：
https://www.postgresql.org/about/news/postgresql-15-rc-1-released-2516/
PostgreSQL 15 RC1相比beta4版本的主要变化是做了如下bug修复：
- The syntax for publishing all tables in a schema using logical replication is changed to CREATE PUBLICATION … FOR TABLES IN SCHEMA …
- Logical replication publications can now publish tables that are within a schema if both schema and table are specified.
- Disallow publishing a schema if a table with column-lists is specified.
- Fix issue with pg_publication_tables view where it would display dropped columns.
- Disallow creating a new database with an unsupported ICU locale.
- Fix behavior issue with the --gzip option for pg_basebackup where the contents of the WAL directory were not compressed.
- Fix issue with recovery prefetching when maintenance_io_concurrency was set to a low value (e.g. 0).
- Log errors when replaying WAL files when wal_compression is specified as either lz4 or zstd but the server does not support it.
- Move several files generated by pg_upgrade to an internal subdirectory.
- Clear the display from the ps command when the recovery process finishes.
可以看出最主要的修复是逻辑复制相关的bug，这也难怪，15对逻辑复制增加了很多新特性。
官方release说明比较简要，下面进一步进行分析：
1.逻辑复制针对schema发布所有表简化语法
15 RC1之前的语法是：
CREATE PUBLICATION ... FOR ALL TABLES IN SCHEMA ....
15 RC1简化为：
CREATE PUBLICATION ... FOR TABLES IN SCHEMA ....
去掉了ALL关键字，既然已经TABLES了，ALL有点多余了。
2.逻辑复制修改发布时相同schema下仍可添加带schema前缀的table
15 RC1之前会出现下面的报错：
logical_src=# alter publication pub_comp add table s3.s3_tab3;
ERROR: cannot add relation "s3.s3_tab3" to publication
DETAIL: Table's schema "s3" is already part of the publication or part of the specified schema list.
15 RC1修复了这个问题。
3.逻辑复制混合发布table和schema时限制table不能为部分列
15 RC1混合发布表和schema下的所有表时，限制表不能为部分列，具体可以参考下面的示例：
logical_src=# create publication pub_comp2 for table tab2(id,info2), tables in schema s3;
ERROR: cannot use publication column list for relation "public.tab2"
DETAIL: Column list cannot be specified if any schema is part of the publication or specified in the list.
混合发布时，对单表必须全部发布，不能是部分列。
4.逻辑复制发布表视图pg_publication_tables修复显示删除的列
参考下面的示例：
create table t1(i serial primary key);
alter table t1 drop i;
alter table t1 add id serial primary key;
create publication pub_t1 for table t1;
select * from pg_publication_tables where pubname = 'pub_t1' \gx
attnames列显示的信息不正常
-[ RECORD 1 ]---------------------------------
pubname | pub_t1
schemaname | public
tablename | t1
attnames | {........pg.dropped.1........,id}
rowfilter |
15 RC1显示正常如下：
-[ RECORD 1 ]------
pubname | pub_t1
schemaname | public
tablename | t1
attnames | {id}
rowfilter |
5.修复创建数据库时如果encoding与ICU locale不匹配时及早提示
15 RC1之前创建数据库时如果encoding与ICU locale不匹配，可以创建成功
createdb --encoding SQL_ASCII --locale-provider icu --icu-locale en-US --template template0 mydb
使用时才会报错：
psql -c "SELECT 'a' < 'b'" mydb
ERROR: encoding "SQL_ASCII" not supported by ICU
15 RC1在创建时会直接提示错误：
createdb --encoding SQL_ASCII --locale-provider icu --icu-locale en-US --template template0 mydb
createdb: error: database creation failed: ERROR: encoding "SQL_ASCII" is not supported with ICU provider
6.pg_basebackup基础备份gzip选项值bug修复
详细示例请参考：
https://www.postgresql.org/message-id/1400032.1662217889@sss.pgh.pa.us
7.修复recovery_prefetch=on和maintenance_io_concurency=0时失败的场景
详细示例请参考：
https://www.postgresql.org/message-id/flat/20220831140128.GS31833%40telsasoft.com
8.当server未使用"–with-lz4"，"–with-zstd"编译选项而实际设置wal_compression=lz4/zstd时修复报错提示
详细示例请参考：
https://www.postgresql.org/message-id/flat/20220902115511.GY31833%40telsasoft.com#ebfa4e87b4247318ccd1e233c7c9af4a
9.pg_upgrade升级过程中部分文件转移到内部子目录中
详细示例请参考：
https://www.postgresql.org/message-id/181A6DA8-3B7F-4B71-82D5-363FF0146820@yesql.se
10.数据库启动recovery过程清理"recovering NNNNN"日志
详细示例请参考：
https://www.postgresql.org/message-id/flat/20220912005443.GB31833%40telsasoft.com#b900d448bc57e46da3a235219034ba4c
不出意外，PostgreSQL 15将于2022年10月13日正式发布。
相关文章：PostgreSQL beta1-beta4的变化
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