Re: Deleting older versions in unique indexes to avoid page splits

Sorry, hit Send too early.

So, I emulated queue operations(INSERT at the end and DELETE from the head). And also made 5-minute transactions
appear in the background for the whole duration of the test. 3 pgbench were run in parallel on a scale 3000 bench database
with modifications (attached).

Master
------

        relname        |   nrows   | blk_before | mb_before | blk_after | mb_after |  diff
-----------------------+-----------+------------+-----------+-----------+----------+--------
 pgbench_accounts      | 300000000 |    4918033 |   38422.1 |   5065575 |  39574.8 |  +3.0%
 accounts_mtime        | 300000000 |    1155119 |    9024.4 |   1287656 |  10059.8 | +11.5%
 fiver                 | 300000000 |     427039 |    3336.2 |    567755 |   4435.6 | +33.0%
 pgbench_accounts_pkey | 300000000 |     822573 |    6426.4 |   1033344 |   8073.0 | +25.6%
 score                 | 300000000 |     284022 |    2218.9 |    458502 |   3582.0 | +61.4%
 tenner                | 300000000 |     346050 |    2703.5 |    417985 |   3265.5 | +20.8%
(6 rows)

DB size: 65.2..72.3 (+7.1GB / +10.9%)
TPS: 2297 / 495

Patched
------
        relname        |   nrows   | blk_before | mb_before | blk_after | mb_after |  diff
-----------------------+-----------+------------+-----------+-----------+----------+--------
 pgbench_accounts      | 300000000 |    4918033 |   38422.1 |   5067500 |  39589.8 |  +3.0%
 accounts_mtime        | 300000000 |    1155119 |    9024.4 |   1283441 |  10026.9 | +11.1%
 fiver                 | 300000000 |     427039 |    3336.2 |    429101 |   3352.4 |  +0.5%
 pgbench_accounts_pkey | 300000000 |     822573 |    6426.4 |    826056 |   6453.6 |  +0.4%
 score                 | 300000000 |     284022 |    2218.9 |    285465 |   2230.2 |  +0.5%
 tenner                | 300000000 |     346050 |    2703.5 |    347695 |   2716.4 |  +0.5%
(6 rows)

DB size: 65.2..67.5 (+2.3GB / +3.5%)