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ChangeSet
1.2635 05/05/06 17:20:56 paul@stripped +1 -0
internals.texi:
Add markup.
Docs/internals.texi
1.74 05/05/06 17:20:48 paul@stripped +74 -55
Add markup.
# This is a BitKeeper patch. What follows are the unified diffs for the
# set of deltas contained in the patch. The rest of the patch, the part
# that BitKeeper cares about, is below these diffs.
# User: paul
# Host: frost.snake.net
# Root: /Volumes/frost2/MySQL/bk/mysqldoc
--- 1.73/Docs/internals.texi 2005-04-14 18:14:34 -05:00
+++ 1.74/Docs/internals.texi 2005-05-06 17:20:48 -05:00
@@ -57,7 +57,7 @@
* optimizer:: The Optimizer
* Algorithms:: Important Algorithms and Structures
* MySQL column types:: The different column types in MySQL
-* Charsets:: Charsets and Related Issues
+* Charsets:: Character Sets and Related Issues
* selects:: How MySQL Performs Different Selects
* transformations:: How MySQL Transforms Subqueries
* Client/Server Protocol:: MySQL Client/Server Protocol
@@ -389,7 +389,7 @@
The Optimizer
Important Algorithms and Structures
The different column types in MySQL
-Charsets and Related Issues
+Character Sets and Related Issues
How MySQL Performs Different Selects
How MySQL Transforms Subqueries
MySQL Client/Server Protocol
@@ -4508,74 +4508,93 @@
@section VARCHAR type
@itemize @bullet
+
+@item
+In old tables (from MySQL 4.1 and earlier), @code{VARCHAR} columns have type
+@code{MYSQL_TYPE_VAR_STRING}, which works exactly like a @code{CHAR} with
+the exception that if you do an @code{ALTER TABLE}, it's converted to a true
+@code{VARCHAR} (@code{MYSQL_TYPE_VARCHAR}). (This means that old tables
+will work as before for users)
+
+@item
+Apart from the above case, there is not anymore any automatic changes from
+@code{CHAR} to @code{VARCHAR} or from @code{VARCHAR} to @code{CHAR}. MySQL
+will remember the used type and stick to it.
+
+@item
+@code{VARCHAR} is implemented in @file{field.h} and @file{field.cc} through
+the new class @code{Field_varstring}.
+
+@item
+@code{MyISAM} implements @code{VARCHAR} both for dynamic-length and
+fixed-length rows (as signaled with the @code{ROW_FORMAT} flag)
+
@item
-In old tables (from MySQL 4.1 and below) VARCHAR fields have type
-MYSQL_TYPE_VAR_STRING, which works exactly like a CHAR with the
-exception that if you do an ALTER TABLE it's converted to a true
-VARCHAR (MYSQL_TYPE_VARCHAR).
-(This means that old tables will work as before for users)
-@item
-Apart from the above case, there is not anymore any automatic changes
-from CHAR to VARCHAR or from VARCHAR to CHAR. MySQL will remember the
-used type and stick to it.
-@item
-VARCHAR is implemented in field.h and field.cc through the
-new class Field_varstring.
-@item
-MyISAM implements VARCHAR both for dynamic length and fixed length
-rows (as signaled with the ROW_FORMAT flag)
-@item
-The main difference between VARCHAR and CHAR is that VARCHAR stores end
-space. (If end space doesn't fit into the column, this is an error in
-strict mode). Note that end space are not significant in compare or for
-unique; In this case VARCHAR works just like CHAR.
+The main difference between @code{VARCHAR} and @code{CHAR} is that
+@code{VARCHAR} stores end space. (If end space doesn't fit into the column,
+this is an error in strict mode). Note that end space are not significant in
+comparisons or for unique. In this case, @code{VARCHAR} works just like
+@code{CHAR}.
+
@item
-In table->record there is reserved a fixed amount of space for
+In @code{table->record}, there is reserved a fixed amount of space for
the varchar lengths (1 or 2 bytes) + data.
+
@item
-If VARCHAR storage length <= 255 then we use 1 byte length, else a 2
-byte length. This gives us 65535 as a maximum size for VARCHAR (for
-multi-byte character sets the maximum size is of course smaller).
+If @code{VARCHAR} storage length <= 255, then we use 1-byte length, else a
+2-byte length. This gives us 65535 as a maximum size for @code{VARCHAR} (for
+multi-byte character sets, the maximum size is of course smaller).
+
@item
The number of bytes used to store the length is in the field
-Field_varchar->length_bytes. Note that internally this can be 2 even if
-Field_varchar->field_length < 256 (for example for a shortened key to a
-varchar(256)).
+@code{Field_varchar->length_bytes}. Note that internally this can be 2 even if
+@code{Field_varchar->field_length} < 256 (for example, for a shortened key to a
+@code{varchar(256)}).
+
@item
-There is a new macro: HA_VARCHAR_PACKLENGTH(field_length) that can be
-used on field->length in write_row / read_row to check how many length
+There is a new macro, @code{HA_VARCHAR_PACKLENGTH(field_length)}, that can be
+used on @code{field->length} in write_row / read_row to check how many length
bytes are used. (In this context we can't have a field_length < 256 with
-a 2 byte pack length)
+a 2-byte pack length)
+
+@item
+When creating a key for the handler, @code{HA_KEYTYPE_VARTEXT1} and
+@code{HA_KEYTYPE_BINARY1} are used for a key on a column that has a 1-byte
+length prefix and @code{HA_KEYTYPE_VARTEXT2} and @code{HA_KEYTYPE_BINARY2}
+for a column that has a 2-byte length prefix. (In the future we will
+probably delete @code{HA_KEYTYPE_BINARY#}, as this can be instead be done by
+just using the @code{binary} character set with @code{HA_KEYTYPE_VARTEXT#})
+
@item
-When creating a key for the handler, HA_KEYTYPE_VARTEXT1 and
-HA_KEYTYPE_BINARY1 are used for a key on a column that has a 1 byte
-length prefix and HA_KEYTYPE_VARTEXT2 and HA_KEYTYPE_BINARY2 for a
-column that has a 2 byte length prefix. (In the future we will probably
-delete HA_KEYTYPE_BINARY# as this can be instead be done by just using
-the binary characterset with HA_KEYTYPE_VARTEXT#)
-@item
-When sending a key to the handler for index_read() or records_in_range,
-we always use a 2 byte length for the VARCHAR to make things simpler.
-(The intention is in 5.1 change CHAR's to also use a 2 byte length for
+When sending a key to the handler for @code{index_read()} or records_in_range,
+we always use a 2-byte length for the @code{VARCHAR} to make things simpler.
+(The intention is in 5.1 change @code{CHAR}'s to also use a 2-byte length for
these functions, as this will speed up and simplify the key handling
code on the handler side)
+
@item
-The test case 'mysql-test/include/varchar.inc' should be include in the
-code that tests the handler, see t/myisam.test for how to use this. You
-should verify the result against the one in mysql-test/t/myisam.result'
-to ensure that you get the correct results.
-@item
-Clients sees both the old and new VARCHAR type as MYSQL_TYPE_VAR_STRING,
-it will never (at least for 5.0) see MYSQL_TYPE_VARCHAR. This is to
-ensure that old clients will work as before.
-@item
-If one runs MySQL 5.0 with the --new option, then MySQL will show old
-VARCHAR columns as 'CHAR' in SHOW CREATE TABLE. (This is useful when
-testing if a table is using the new VARCHAR type or not).
+The test case file @file{mysql-test/include/varchar.inc} should be included
+in the code that tests the handler. See @file{t/myisam.test} for how to use
+this. You should verify the result against the one in
+@file{mysql-test/t/myisam.result} to ensure that you get the correct
+results.
+
+@item
+A client sees both the old and new @code{VARCHAR} type as
+@code{MYSQL_TYPE_VAR_STRING}. It will never (at least for 5.0) see
+@code{MYSQL_TYPE_VARCHAR}. This is to ensure that old clients will work as
+before.
+
+@item
+If you run MySQL 5.0 with the @code{--new} option, MySQL will show old
+@code{VARCHAR} columns as @code{'CHAR'} in @code{SHOW CREATE TABLE}. (This
+is useful when testing whether a table is using the new @code{VARCHAR} type
+or not).
+
@end itemize
@node Charsets, selects, MySQL column types, Top
-@chapter Charsets and Related Issues
+@chapter Character Sets and Related Issues
@menu
* CHARSET_INFO:: @code{CHARSET_INFO} Structure
| Thread |
|---|
| • bk commit - mysqldoc@docsrva tree (paul:1.2635) | paul | 7 May |
