Re: [REVIEW] Re: Compression of full-page-writes

And.. After some more hacking, I have been able to come up with a patch that is able to compress blocks without the page hole, and that keeps the WAL record length the same as HEAD when compression switch is off. The numbers are pretty good, CPU is saved in the same proportions as previous patches when compression is enabled, and there is zero delta with HEAD when compression switch is off.

Here are the actual numbers:
           test_name           | pg_size_pretty | user_diff | system_diff
-------------------------------+----------------+-----------+-------------
 FPW on + 2 bytes, ffactor 50  | 582 MB         | 42.391894 |    0.807444
 FPW on + 2 bytes, ffactor 20  | 229 MB         | 14.330304 |    0.729626
 FPW on + 2 bytes, ffactor 10  | 117 MB         |  7.335442 |    0.570996
 FPW off + 2 bytes, ffactor 50 | 746 MB         | 25.330391 |    1.248503
 FPW off + 2 bytes, ffactor 20 | 293 MB         | 10.537475 |    0.755448
 FPW off + 2 bytes, ffactor 10 | 148 MB         |  5.762775 |    0.763761
 FPW on + 0 bytes, ffactor 50  | 582 MB         | 42.174297 |    0.790596
 FPW on + 0 bytes, ffactor 20  | 229 MB         | 14.424233 |    0.770459
 FPW on + 0 bytes, ffactor 10  | 117 MB         |  7.057195 |    0.584806
 FPW off + 0 bytes, ffactor 50 | 746 MB         | 25.261998 |    1.054516
 FPW off + 0 bytes, ffactor 20 | 293 MB         | 10.589888 |    0.860207
 FPW off + 0 bytes, ffactor 10 | 148 MB         |  5.827191 |    0.874285
 HEAD, ffactor 50              | 746 MB         | 25.181729 |    1.133433
 HEAD, ffactor 20              | 293 MB         |  9.962242 |    0.765970
 HEAD, ffactor 10              | 148 MB         |  5.693426 |    0.775371
 Record, ffactor 50            | 582 MB         | 54.904374 |    0.678204
 Record, ffactor 20            | 229 MB         | 19.798268 |    0.807220
 Record, ffactor 10            | 116 MB         |  9.401877 |    0.668454
(18 rows)

The new tests of this patch are "FPW off + 0 bytes". Patches as well as results are attached.

Regards,

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