This is a regression from the fix for bug no 38999. A storage engine capable
of reading only a subset of a table's columns updates corresponding bits in
the read buffer to signal that it has read NULL values for the corresponding
columns. It cannot, and should not, update any other bits. Bug no 38999
occurred because the implementation of UPDATE statements compare the NULL bits
using memcmp, inadvertently comparing bits that were never requested from the
storage engine. The regression was caused by the storage engine trying to
alleviate the situation by writing to all NULL bits, even those that it had no
knowledge of. This has devastating effects for the index merge algorithm,
which relies on all NULL bits, except those explicitly requested, being left
unchanged.
The fix reverts the fix for bug no 38999 in both InnoDB and InnoDB plugin and
changes the server's method of comparing records. For engines that always read
entire rows, we proceed as usual. For engines capable of reading only select
columns, the record buffers are now compared on a column by column basis. An
assertion was also added so that non comparable buffers are never read. Some
relevant copy-pasted code was also consolidated in a new function.
WL#3397 Refactoring storage engine test cases (for falcon)
It contains also fixes according to code review.
Contents: Testcases which were in history dedicated to InnoDB or MyISAM only.
Modifications:
1. Shift the main testing code into include/<testing field>.inc
Introduce $variables which can be used to omit tests for features which are not supported by
certain storage engines.
2. The storage engine to be tested is assigned within the toplevel script (t/<whatever>_<engine>.test)
via variable $engine_type and the the main testing code is sourced from
include/<testing field>.inc
3. Some toplevel testscripts have to be renamed to
- avoid immediate or future namespace clashes
- show via filename which storage engine is tested
4. Minor code cleanup like remove trailing spaces, some additional comments ....
