E.6. Restrictions On Character Sets; E.7. Limits In Mysql; E.7.1. Limits Of Joins; E.7.2. Limits On Number Of Databases And Tables - Oracle 5.0 Reference Manual

the server itself acts as a TM. Internal XA support is limited by the capabilities of individual storage
engines. Internal XA is required for handling XA transactions that involve more than one storage
engine. The implementation of internal XA requires that a storage engine support two-phase commit at
the table handler level, and currently this is true only for InnoDB.
For START, the
XA
For END, the
XA
The requirement that the
a global transaction is a limitation of the current MySQL XA implementation. It is not part of the XA
specification.
If an XA transaction has reached the
with
kill -9
restarts. However, if the client reconnects and commits the transaction, the transaction will be absent
from the binary log even though it has been committed. This means the data and the binary log have
gone out of synchrony. An implication is that XA cannot be used safely together with replication.
It is possible that the server will roll back a pending XA transaction, even one that has reached the
state. This happens if a client connection terminates and the server continues to run, or if
PREPARED
clients are connected and the server shuts down gracefully. (In the latter case, the server marks each
connection to be terminated, and then rolls back the
should be possible to commit or roll back a
changes to the binary logging mechanism.

E.6. Restrictions on Character Sets

• Identifiers are stored in
can contain only characters in the Basic Multilingual Plane (BMP). Supplementary characters are not
permitted in identifiers.
• The
ucs2
• It cannot be used as a client character set, which means that it does not work for
SET CHARACTER
• It is currently not possible to use
set.
•
FULLTEXT
perform
• The
REGEXP
safe and may produce unexpected results with multi-byte character sets. In addition, these operators
compare characters by their byte values and accented characters may not compare as equal even if
a given collation treats them as equal.

E.7. Limits in MySQL

This section lists current limits in MySQL 5.0.

E.7.1. Limits of Joins

The maximum number of tables that can be referenced in a single join is 61. This also applies to the
number of tables that can be referenced in the definition of a view.

E.7.2. Limits on Number of Databases and Tables

MySQL has no limit on the number of databases. The underlying file system may have a limit on the
number of directories.
Restrictions on Character Sets
and
JOIN RESUME
SUSPEND [FOR MIGRATE]
part of the
bqual
on Unix) or shuts down abnormally, the transaction can be continued after the server
database tables (user, db, and so forth) using utf8, but identifiers
mysql
character sets has the following restrictions:
SET. (See Section 10.1.4, "Connection Character Sets and
indexes cannot be created on a column that this character set. However, you can
searches on the column without an index.
IN BOOLEAN MODE
[899] and [899]
RLIKE
clauses are not supported.
clause is not supported.
value be different for each XA transaction within
xid
state and the MySQL server is killed (for example,
PREPARED
PREPARED
XA transaction, but this cannot be done without
PREPARED
LOAD DATA INFILE
operators work in byte-wise fashion, so they are not multi-byte
2988
XA transaction associated with it.) It
to load data files that use this character
or
SET NAMES
Collations".)