Hi there,
I notice a little strange things of clog behaviours. When I create a test table, say, a_test, the table only contains a INT type column. postgres=# CREATE TABLE a_test (n INT); CREATE TABLE and then insert one tuple: postgres=# INSERT INTO a_test VALUES (1); INSERT 0 1 And then quit, shutdown the database. [jet@halodev-jet-01 pg_xact]$ pg_ctl stopwaiting for server to shut down....2024-12-23 12:05:46.568 CST [1340130] LOG: received fast shutdown request 2024-12-23 12:05:46.577 CST [1340130] LOG: aborting any active transactions 2024-12-23 12:05:46.579 CST [1340130] LOG: background worker "logical replication launcher" (PID 1340136) exited with exit code 1 2024-12-23 12:05:46.579 CST [1340131] LOG: shutting down 2024-12-23 12:05:46.583 CST [1340131] LOG: checkpoint starting: shutdown immediate 2024-12-23 12:05:46.604 CST [1340131] LOG: checkpoint complete: wrote 21 buffers (0.1%); 0 WAL file(s) added, 0 removed, 0 recycled; write=0.002 s, sync=0.011 s, total=0.025 s; sync files=17, longest=0.005 s, average=0.001 s; distance=88 kB, estimate=88 kB; lsn=0/1554658, redo lsn=0/1554658 2024-12-23 12:05:46.607 CST [1340130] LOG: database system is shut down done server stopped After database stopped, change to the pg_xact directory, and delete the clog file, and then create a dummy clog file. [jet@halodev-jet-01 pg_xact]$ ls -ltrtotal 8 -rw-rw-r--. 1 jet jet 8192 Dec 23 12:05 0000 [jet@halodev-jet-01 pg_xact]$ rm -f 0000 [jet@halodev-jet-01 pg_xact]$ dd if=/dev/zero of=./0000 bs=1024 count=8 8+0 records in 8+0 records out 8192 bytes (8.2 kB, 8.0 KiB) copied, 8.5894e-05 s, 95.4 MB/s And then start the database. [jet@halodev-jet-01 pg_xact]$ pg_ctl startwaiting for server to start....2024-12-23 12:06:01.935 CST [1340148] LOG: starting PostgreSQL 16.6 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 8.5.0 20210514 (Red Hat 8.5.0-4), 64-bit 2024-12-23 12:06:01.936 CST [1340148] LOG: listening on IPv6 address "::1", port 5432 2024-12-23 12:06:01.936 CST [1340148] LOG: listening on IPv4 address "127.0.0.1", port 5432 2024-12-23 12:06:01.943 CST [1340148] LOG: listening on Unix socket "/tmp/.s.PGSQL.5432" 2024-12-23 12:06:01.950 CST [1340151] LOG: database system was shut down at 2024-12-23 12:05:46 CST 2024-12-23 12:06:01.956 CST [1340148] LOG: database system is ready to accept connections done server started The database started normally. But the INSERT transaction was lost: [jet@halodev-jet-01 pg_xact]$ psqlpsql (16.6) Type "help" for help. postgres=# SELECT * FROM a_test; n --- (0 rows) postgres=# BUT! If I do the same steps above, and the only difference is after INSERT, I just do a simple query SELECT * FROM a_test; the INSERT transaction still exists. How could this happen? What's the difference after SELECT? [jet@halodev-jet-01 pg_xact]$ psqlpsql (16.6) Type "help" for help. postgres=# INSERT INTO a_test VALUES (1); INSERT 0 1 postgres=# SELECT * FROM a_test; n --- 1 (1 row) postgres=# \q [jet@halodev-jet-01 pg_xact]$ pg_ctl stop waiting for server to shut down....2024-12-23 12:13:36.577 CST [1340148] LOG: received fast shutdown request 2024-12-23 12:13:36.583 CST [1340148] LOG: aborting any active transactions 2024-12-23 12:13:36.584 CST [1340148] LOG: background worker "logical replication launcher" (PID 1340154) exited with exit code 1 2024-12-23 12:13:36.585 CST [1340149] LOG: shutting down 2024-12-23 12:13:36.587 CST [1340149] LOG: checkpoint starting: shutdown immediate 2024-12-23 12:13:36.601 CST [1340149] LOG: checkpoint complete: wrote 2 buffers (0.0%); 0 WAL file(s) added, 0 removed, 0 recycled; write=0.001 s, sync=0.006 s, total=0.017 s; sync files=2, longest=0.004 s, average=0.003 s; distance=0 kB, estimate=0 kB; lsn=0/15548E8, redo lsn=0/15548E8 2024-12-23 12:13:36.603 CST [1340148] LOG: database system is shut down done server stopped [jet@halodev-jet-01 pg_xact]$ rm -f 0000 [jet@halodev-jet-01 pg_xact]$ dd if=/dev/zero of=./0000 bs=1024 count=8 8+0 records in 8+0 records out 8192 bytes (8.2 kB, 8.0 KiB) copied, 8.9862e-05 s, 91.2 MB/s [jet@halodev-jet-01 pg_xact]$ pg_ctl start waiting for server to start....2024-12-23 12:13:48.430 CST [1340205] LOG: starting PostgreSQL 16.6 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 8.5.0 20210514 (Red Hat 8.5.0-4), 64-bit 2024-12-23 12:13:48.430 CST [1340205] LOG: listening on IPv6 address "::1", port 5432 2024-12-23 12:13:48.430 CST [1340205] LOG: listening on IPv4 address "127.0.0.1", port 5432 2024-12-23 12:13:48.437 CST [1340205] LOG: listening on Unix socket "/tmp/.s.PGSQL.5432" 2024-12-23 12:13:48.445 CST [1340208] LOG: database system was shut down at 2024-12-23 12:13:36 CST 2024-12-23 12:13:48.451 CST [1340205] LOG: database system is ready to accept connections done server started [jet@halodev-jet-01 pg_xact]$ psql psql (16.6) Type "help" for help. postgres=# SELECT * FROM a_test; n --- 1 (1 row) Jet
