The issue was a bad merge of MDEV-12253 from 10.1 to 10.2
in commit f9cc391863ab962e8c8a8a8a676d730498eb8d6f.
In that merge, I wrongly assumed that all test file conflicts
for mysql-test/suite/encryption had been properly resolved in
bb-10.2-MDEV-12253 (commit 76aa6be77635c7017459ce33b41c837c9acb606d)
while in fact, some files there had been copied from the 10.1 branch.
This commit is based on a manually done conflict resolution of
the mysql-test/suite/encryption on the same merge, applied to
the current 10.2 branch.
As part of this commit, the test encryption.innodb-bad-key-change4
which was shortly disabled due to MDEV-11336 will be re-enabled again.
(While the test enables innodb_defragment, it does not fail even though
enabling innodb_defragment currently has no effect.)
Analysis: By design InnoDB was reading first page of every .ibd file
at startup to find out is tablespace encrypted or not. This is
because tablespace could have been encrypted always, not
encrypted newer or encrypted based on configuration and this
information can be find realible only from first page of .ibd file.
Fix: Do not read first page of every .ibd file at startup. Instead
whenever tablespace is first time accedded we will read the first
page to find necessary information about tablespace encryption
status.
TODO: Add support for SYS_TABLEOPTIONS where all table options
encryption information included will be stored.
