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3 Commits

Author SHA1 Message Date
Eugene Kosov
fae1319450 MDEV-19524 Server crashes in Bitmap<64u>::is_clear_all / Field_longstr::csinfo_change_allows_instant_alter
compare_keys_but_name(): reorder checks to ensure that
new_field->field != NULL inside Field::is_equal()
2019-05-21 08:09:19 +04:00
Alexander Barkov
c59d6395a6 A joint patch for MDEV-19284 and MDEV-19285 (INSTANT ALTER)
This patch fixes:

- MDEV-19284 INSTANT ALTER with ucs2-to-utf16 conversion produces bad data
- MDEV-19285 INSTANT ALTER from ascii_general_ci to latin1_general_ci produces corrupt data

These regressions were introduced in 10.4.3 by:
- MDEV-15564 Avoid table rebuild in ALTER TABLE on collation or charset changes

Changes:

1. Cleanup: Adding a helper method
   Field_longstr::csinfo_change_allows_instant_alter(),
   to remove some duplicate code in field.cc.

2. Cleanup: removing Type_handler::Charsets_are_compatible() and static
   function charsets_are_compatible() and
   introducing new methods in the recently added class Charset instead:
   - encoding_allows_reinterpret_as()
   - encoding_and_order_allow_reinterpret_as()

3. Bug fix: Removing the code that allowed instant conversion for
   ascii-to->8bit and ucs2-to->utf16.
   This actually fixes MDEV-19284 and MDEV-19285.

4. Bug fix: Adding a helper method Charset::collation_specific_name().
   The old corresponding code in Type_handler::Charsets_are_compatible()
   was not safe against (badly named) user-defined collations whose
   character set name can be longer than collation name.
2019-05-16 16:20:25 +04:00
Marko Mäkelä
ea0be9e2d6 MDEV-15564 Avoid table rebuild in ALTER TABLE on collation or charset changes
Allow ALGORITHM=INSTANT (or avoid touching any data)
when changing the collation, or in some cases, the character set,
of a non-indexed CHAR or VARCHAR column. There is no penalty
for subsequent DDL or DML operations, and compatibility with
older MariaDB versions will be unaffected.

Character sets may be changed when the old encoding is compatible
with the new one. For example, changing from ASCII to anything
ASCII-based, or from 3-byte to 4-byte UTF-8 can sometimes be
performed instantly.

This is joint work with Eugene Kosov.
The test cases as well as ALTER_CONVERT_TO, charsets_are_compatible(),
Type_handler::Charsets_are_compatible() are his work.
The Field_str::is_equal(), Field_varstring::is_equal() and
the InnoDB changes were mostly rewritten by me due to conflicts
with MDEV-15563.

Limitations:

Changes of indexed columns will still require
ALGORITHM=COPY. We should allow ALGORITHM=NOCOPY and allow
the indexes to be rebuilt inside the storage engine,
without copying the entire table.

Instant column size changes (in bytes) are not supported by
all storage engines.

Instant CHAR column changes are only allowed for InnoDB
ROW_FORMAT=REDUNDANT. We could allow this for InnoDB
when the CHAR internally uses a variable-length encoding,
say, when converting from 3-byte UTF-8 to 4-byte UTF-8.

Instant VARCHAR column changes are allowed for InnoDB
ROW_FORMAT=REDUNDANT, and for others only if the size
in bytes does not change from 128..255 bytes to more
than 256 bytes.

Inside InnoDB, this slightly changes the way how MDEV-15563
works and fixes the result of the innodb.instant_alter_extend test.
We change the way how ALTER_COLUMN_EQUAL_PACK_LENGTH_EXT
is handled. All column extension, type changes and renaming
now go through a common route, except when ctx->is_instant()
is in effect, for example, instant ADD or DROP COLUMN has
been initiated. Only in that case we will go through
innobase_instant_try() and rewrite all column metadata.

get_type(field, prtype, mtype, len): Convert a SQL data type into
InnoDB column metadata.

innobase_rename_column_try(): Remove the update of SYS_COLUMNS.

innobase_rename_or_enlarge_column_try(): New function,
replacing part of innobase_rename_column_try() and all of
innobase_enlarge_column_try(). Also changes column types.

innobase_rename_or_enlarge_columns_cache(): Also change
the column type.
2019-02-14 20:17:14 +02:00