I verified the patch "v2-0001-Free-disk-space-for-dropped-relations-on-commit.patch" on master branch
"0cc99327888840f2bf572303b68438e4caf62de9".It works for me. Below is my test procedure and results.
=== Before the patch ===
#1 from psql console 1, create table and index then insert enough data
postgres=# CREATE TABLE test_tbl ( a int, b text);
postgres=# CREATE INDEX idx_test_tbl on test_tbl (a);
postgres=# INSERT INTO test_tbl SELECT generate_series(1,80000000),'Hello world!';
postgres=# INSERT INTO test_tbl SELECT generate_series(1,80000000),'Hello world!';
#2 check files size
david:12867$ du -h
12G .
#3 from psql console 2, drop the index
postgres=# drop index idx_test_tbl;
#4 check files size in different ways,
david:12867$ du -h
7.8G .
david:12867$ ls -l
...
-rw------- 1 david david 0 Nov 23 20:07 16402
...
$ lsof -nP | grep '(deleted)' |grep pgdata
...
postgres 25736 david 45u REG 259,2 0 12592758
/home/david/sandbox/postgres/pgdata/base/12867/16402(deleted)
postgres 25736 david 49u REG 259,2 1073741824 12592798
/home/david/sandbox/postgres/pgdata/base/12867/16402.1(deleted)
postgres 25736 david 53u REG 259,2 1073741824 12592739
/home/david/sandbox/postgres/pgdata/base/12867/16402.2(deleted)
postgres 25736 david 59u REG 259,2 372604928 12592800
/home/david/sandbox/postgres/pgdata/base/12867/16402.3(deleted)
...
The index relnode id "16402" displays size "0" from postgres database folder, but when using lsof to check, all 16402.x
arestill in used by a psql connection except 16402 is set to 0. Check it again after an hour, lsof shows the same
results.
=== After the patch ===
Repeat step 1 ~ 4, lsof shows all the index relnode files (in this case, the index relnode id 16389) are removed within
about1 minute.
$ lsof -nP | grep '(deleted)' |grep pgdata
...
postgres 32707 david 66u REG 259,2 0 12592763
/home/david/sandbox/postgres/pgdata/base/12867/16389.1(deleted)
postgres 32707 david 70u REG 259,2 0 12592823
/home/david/sandbox/postgres/pgdata/base/12867/16389.2(deleted)
postgres 32707 david 74u REG 259,2 0 12592805
/home/david/sandbox/postgres/pgdata/base/12867/16389.3(deleted)
...
One thing interesting for me is that, if the index is created after data records has been inserted, then lsof doesn't
showthis issue.
