國慶之際，PostgreSQL全球開發組發布了15 RC1，文章鏈接如下：
https://www.postgresql.org/about/news/postgresql-15-rc-1-released-2516/
PostgreSQL 15 RC1相比beta4版本的主要變化是做了如下bug修復：
- 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復是邏輯復制相關的bug，這也難怪，15對邏輯復制增加了很多新特性。
官方release說明比較簡要，下面進一步進行分析：
1.邏輯復制針對schema發布所有表簡化語法
15 RC1之前的語法是：
CREATE PUBLICATION ... FOR ALL TABLES IN SCHEMA ....
15 RC1簡化為：
CREATE PUBLICATION ... FOR TABLES IN SCHEMA ....
去掉了ALL關鍵字，既然已經TABLES了，ALL有點多余了。
2.邏輯復制修改發布時相同schema下仍可添加帶schema前綴的table
15 RC1之前會出現下面的報錯：
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修復了這個問題。
3.邏輯復制混合發布table和schema時限制table不能為部分列
15 RC1混合發布表和schema下的所有表時，限制表不能為部分列，具體可以參考下面的示例：
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.
混合發布時，對單表必須全部發布，不能是部分列。
4.邏輯復制發布表視圖pg_publication_tables修復顯示刪除的列
參考下面的示例：
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列顯示的信息不正常
-[ RECORD 1 ]---------------------------------
pubname | pub_t1
schemaname | public
tablename | t1
attnames | {........pg.dropped.1........,id}
rowfilter |
15 RC1顯示正常如下：
-[ RECORD 1 ]------
pubname | pub_t1
schemaname | public
tablename | t1
attnames | {id}
rowfilter |
5.修復創建數據庫時如果encoding與ICU locale不匹配時及早提示
15 RC1之前創建數據庫時如果encoding與ICU locale不匹配，可以創建成功
createdb --encoding SQL_ASCII --locale-provider icu --icu-locale en-US --template template0 mydb
使用時才會報錯：
psql -c "SELECT 'a' < 'b'" mydb
ERROR: encoding "SQL_ASCII" not supported by ICU
15 RC1在創建時會直接提示錯誤：
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基礎備份gzip選項值bug修復
詳細示例請參考：
https://www.postgresql.org/message-id/1400032.1662217889@sss.pgh.pa.us
7.修復recovery_prefetch=on和maintenance_io_concurency=0時失敗的場景
詳細示例請參考：
https://www.postgresql.org/message-id/flat/20220831140128.GS31833%40telsasoft.com
8.當server未使用"–with-lz4"，"–with-zstd"編譯選項而實際設置wal_compression=lz4/zstd時修復報錯提示
詳細示例請參考：
https://www.postgresql.org/message-id/flat/20220902115511.GY31833%40telsasoft.com#ebfa4e87b4247318ccd1e233c7c9af4a
9.pg_upgrade升級過程中部分文件轉移到內部子目錄中
詳細示例請參考：
https://www.postgresql.org/message-id/181A6DA8-3B7F-4B71-82D5-363FF0146820@yesql.se
10.數據庫啟動recovery過程清理"recovering NNNNN"日志
詳細示例請參考：
https://www.postgresql.org/message-id/flat/20220912005443.GB31833%40telsasoft.com#b900d448bc57e46da3a235219034ba4c
不出意外，PostgreSQL 15將于2022年10月13日正式發布。
相關文章：PostgreSQL beta1-beta4的變化
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