Also fixes:
MDEV-32190 Index corruption with unique key and nopad collation (without DESC or HASH keys)
MDEV-28328 Assertion failures in btr0cur.cc upon INSERT or in row0sel.cc afterwards
The code in strings/strcoll.inl when comparing an empty string
to a string like 0x0001050001 did not take into account
that the leftmost weight in the latter can be zero, while
there are some more weights can follow the zero weight.
Rewriting the code to treat the shorter string as smaller than
a longer string.
This is a non-functional change. It changes the way how case folding data
and weight data (for simple Unicode collations) are stored:
- Removing data types MY_UNICASE_CHARACTER, MY_UNICASE_INFO
- Using data types MY_CASEFOLD_CHARACTER, MY_CASEFOLD_INFO instead.
This patch changes simple Unicode collations in a similar way
how MDEV-30695 previously changed Asian collations.
No new MTR tests are needed. The underlying code is thoroughly
covered by a number of ctype_*_ws.test and ctype_*_casefold.test
files, which were added recently as a preparation
for this change.
Old and new Unicode data layout
-------------------------------
Case folding data is now stored in separate tables
consisting of MY_CASEFOLD_CHARACTER elements with two members:
typedef struct casefold_info_char_t
{
uint32 toupper;
uint32 tolower;
} MY_CASEFOLD_CHARACTER;
while weight data (for simple non-UCA collations xxx_general_ci
and xxx_general_mysql500_ci) is stored in separate arrays of
uint16 elements.
Before this change case folding data and simple weight data were
stored together, in tables of the following elements with three members:
typedef struct unicase_info_char_st
{
uint32 toupper;
uint32 tolower;
uint32 sort; /* weights for simple collations */
} MY_UNICASE_CHARACTER;
This data format was redundant, because weights (the "sort" member) were
needed only for these two simple Unicode collations:
- xxx_general_ci
- xxx_general_mysql500_ci
Adding case folding information for Unicode-14.0.0 using the old
format would waste memory without purpose.
Detailed changes
----------------
- Changing the underlying data types as described above
- Including unidata-dump.c into the sources.
This program was earlier used to dump UnicodeData.txt
(e.g. https://www.unicode.org/Public/14.0.0/ucd/UnicodeData.txt)
into MySQL / MariaDB source files.
It was originally written in 2002, but has not been distributed yet
together with MySQL / MariaDB sources.
- Removing the old format Unicode data earlier dumped from UnicodeData.txt
(versions 3.0.0 and 5.2.0) from ctype-utf8.c.
Adding Unicode data in the new format into separate header files,
to maintain the code easier:
- ctype-unicode300-casefold.h
- ctype-unicode300-casefold-tr.h
- ctype-unicode300-general_ci.h
- ctype-unicode300-general_mysql500_ci.h
- ctype-unicode520-casefold.h
- Adding a new file ctype-unidata.c as an aggregator for
the header files listed above.
- Adding a new argument "flag" to MY_COLLATION_HANDLER::strnncollsp_nchars()
and a flag MY_STRNNCOLLSP_NCHARS_EMULATE_TRIMMED_TRAILING_SPACES.
The flag defines if strnncollsp_nchars() should emulate trailing spaces
which were possibly trimmed earlier (e.g. in InnoDB CHAR compression).
This is important for NOPAD collations.
For example, with this input:
- str1= 'a ' (Latin letter a followed by one space)
- str2= 'a ' (Latin letter a followed by two spaces)
- nchars= 3
if the flag is given, strnncollsp_nchars() will virtually restore
one trailing space to str1 up to nchars (3) characters and compare two
strings as equal:
- str1= 'a ' (one extra trailing space emulated)
- str2= 'a ' (as is)
If the flag is not given, strnncollsp_nchars() does not add trailing
virtual spaces, so in case of a NOPAD collation, str1 will be compared
as less than str2 because it is shorter.
- Field_string::cmp_prefix() now passes the new flag.
Field_varstring::cmp_prefix() and Field_blob::cmp_prefix() do
not pass the new flag.
- The branch in cmp_whole_field() in storage/innobase/rem/rem0cmp.cc
(which handles the CHAR data type) now also passed the new flag.
- Fixing UCA collations to respect the new flag.
Other collations are possibly also affected, however
I had no success in making an SQL script demonstrating the problem.
Other collations will be extended to respect this flags in a separate
patch later.
- Changing the meaning of the last parameter of Field::cmp_prefix()
from "number of bytes" (internal length)
to "number of characters" (user visible length).
The code calling cmp_prefix() from handler.cc was wrong.
After this change, the call in handler.cc became correct.
The code calling cmp_prefix() from key_rec_cmp() in key.cc
was adjusted according to this change.
- Old strnncollsp_nchar() related tests in unittest/strings/strings-t.c
now pass the new flag.
A few new tests also were added, without the flag.
