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Overview
| Comment: | Polishing pass on the new Unicode material in the user manual. |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA3-256: | 8469cf623de79670cb0e76a1e5f95bf5 |
| User & Date: | tangent 2018-07-27 04:39:12 |
Context
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2018-07-27
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| 04:45 | Modified the "most economically valuable" stuff in the userman's Unicode chapter to handle the "except for emoji" case. check-in: 0bd33dc4fc user: tangent tags: trunk | |
| 04:39 | Polishing pass on the new Unicode material in the user manual. check-in: 8469cf623d user: tangent tags: trunk | |
| 04:34 | Updated user manual Docbook version from 4.2 to 4.4, effectively dropping CentOS 3 and 4 as build platforms, since the current Homebrew Docbook XSL stylesheets throw lots of errors if you specify 4.2 or 4.3. Updated the user manual's README.txt file accordingly. check-in: 3b3678d64e user: tangent tags: trunk | |
Changes
Changes to doc/userman/unicode.dbx.
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Thompson <ulink
url="http://www.cl.cam.ac.uk/~mgk25/ucs/utf-8-history.txt">invented</ulink>
the <ulink url="http://en.wikipedia.org/wiki/UTF-8">UTF-8
encoding</ulink>. UTF-8 is a superset of 7-bit ASCII and is
compatible with C strings, since it doesn’t use 0 bytes
anywhere as multi-byte Unicode encodings do. As a result, many
programs that deal in text will cope with UTF-8 data even though
they have no explicit support for UTF-8. (Follow the last link above
to see how the design of UTF-8 allows this.) Thus, when explicit
support for Unicode was added in MySQL v4.1, they chose to make
UTF-8 the native encoding, to preserve backward compatibility with
programs that had no Unicode support.</para>
</sect2>
<sect2 id="unicode-mysql">
<title>Unicode in MySQL</title>
<para>Since MySQL comes out of the Unix world, and it predates the
widespread use of UTF-8 in Unix, it started out not supporting
Unicode at all. You could store raw UTF-8 strings in old versions of
MySQL, but it wouldn’t know how to do things like sort a
column of UTF-8 strings.</para>
<para>MySQL 4.1 added the first true support for Unicode. This
version of MySQL supported only the BMP, meaning that if you told it
to expect strings to be in UTF-8, it could only use up to 3 bytes
per character.</para>
<para>MySQL 5.5 was the first release to completely support Unicode.
Because the BMP-only Unicode support had been in the wild for about
6 yeras by that point, and changing to the new character set
requires a table rebuild, the new one was called
“utf8mb4” rather than change the longstanding meaning
of “utf8” in MySQL. This release also added a new
alias for the old UTF-8 subset character set,
“utf8mb3.”</para>
<para>Finally, in MySQL 8.0, “utf8mb4” became the
................................................................................
<para>As of MySQL++ 3.2.4, we’ve defined the
<varname>MYSQLPP_UTF8_CS</varname> and
<varname>MYSQLPP_UTF8_COL</varname> macros which expand to
“utf8mb4” and “utf8mb4_general_ci” when
you build MySQL++ against MySQL 5.5 and newer and to
“utf8” and “utf8_general_ci” otherwise.
We use these macros in our <filename>resetdb</filename>
example.</para>
</sect2>
<sect2 id="unicode-unix">
<title>Unicode on Unixy Systems</title>
<para>Linux and Unix have system-wide UTF-8 support these days. If
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Thompson <ulink
url="http://www.cl.cam.ac.uk/~mgk25/ucs/utf-8-history.txt">invented</ulink>
the <ulink url="http://en.wikipedia.org/wiki/UTF-8">UTF-8
encoding</ulink>. UTF-8 is a superset of 7-bit ASCII and is
compatible with C strings, since it doesn’t use 0 bytes
anywhere as multi-byte Unicode encodings do. As a result, many
programs that deal in text will cope with UTF-8 data even though
they have no explicit support for UTF-8. Follow the last link above
to see how the design of UTF-8 allows this.</para>
</sect2>
<sect2 id="unicode-mysql">
<title>Unicode in MySQL</title>
<para>Since MySQL comes out of the Unix world, and it predates the
widespread use of UTF-8 in Unix, the early versinos of MySQL had no
explicit support for Unicode. From the start, you could store raw
UTF-8 strings, but it wouldn’t know how to do things like
sort a column of UTF-8 strings.</para>
<para>MySQL 4.1 added the first explicit support for Unicode. This
version of MySQL supported only the BMP, meaning that if you told it
to expect strings to be in UTF-8, it could only use up to 3 bytes
per character.</para>
<para>MySQL 5.5 was the first release to completely support Unicode.
Because the BMP-only Unicode support had been in the wild for about
6 years by that point, and changing to the new character set
requires a table rebuild, the new one was called
“utf8mb4” rather than change the longstanding meaning
of “utf8” in MySQL. This release also added a new
alias for the old UTF-8 subset character set,
“utf8mb3.”</para>
<para>Finally, in MySQL 8.0, “utf8mb4” became the
................................................................................
<para>As of MySQL++ 3.2.4, we’ve defined the
<varname>MYSQLPP_UTF8_CS</varname> and
<varname>MYSQLPP_UTF8_COL</varname> macros which expand to
“utf8mb4” and “utf8mb4_general_ci” when
you build MySQL++ against MySQL 5.5 and newer and to
“utf8” and “utf8_general_ci” otherwise.
We use these macros in our <filename>resetdb</filename> example;
you're welcome to use them in your code as well.</para>
</sect2>
<sect2 id="unicode-unix">
<title>Unicode on Unixy Systems</title>
<para>Linux and Unix have system-wide UTF-8 support these days. If
|