Oracle 5.0 Reference Manual page 1546

SELECT * FROM t WHERE b 1;
SELECT * FROM t WHERE d = '1';
SELECT * FROM t;
SELECT b,c WHERE a = 1;
This is because, of these four queries, the first uses an index scan, the second and third use
table scans, and the fourth, while using a primary key lookup, does not retrieve the value of any
BLOB
You can help minimize issues with shared read locks by avoiding queries that use primary key
lookups or unique key lookups to retrieve
queries are not avoidable, by committing transactions as soon as possible afterward.
We are working on overcoming this limitation in a future MySQL Cluster release (see Bug
#49190); however, we do not plan to backport any fix for this issue to MySQL 5.0.
• Rollbacks.
key or similar error aborts the entire transaction, and subsequent statements raise
(HY000): Got error 4350 'Transaction already aborted' from
such cases, you must issue an explicit
This behavior differs from that of other transactional storage engines such as
back individual statements.
• Transactions and memory usage.
As noted elsewhere in this chapter, MySQL Cluster does not handle large transactions well; it
is better to perform a number of small transactions with a few operations each than to attempt a
single large transaction containing a great many operations. Among other considerations, large
transactions require very large amounts of memory. Because of this, the transactional behavior of a
number of MySQL statements is effected as described in the following list:
•
TRUNCATE TABLE
empty the table, then it must be re-run until it is successful.
•
DELETE FROM
many rows, you may find that performance is improved by using several
LIMIT ...
you may wish to use
•
LOAD DATA
LOAD DATA FROM MASTER
•
ALTER TABLE
creation of the copy is nontransactional. (In any case, this operation is rolled back when the copy
is deleted.)
17.1.5.4. MySQL Cluster Error Handling
Starting, stopping, or restarting a node may give rise to temporary errors causing some transactions to
fail. These include the following cases:
Known Limitations of MySQL Cluster
or columns.
TEXT
There are no partial transactions, and no partial rollbacks of transactions. A duplicate
is not transactional when used on
(even with no
WHERE
statements to "chunk" the delete operation. If your objective is to empty the table, then
TRUNCATE TABLE
statements.
LOAD DATA INFILE
Important
When executing a
performs commits at irregular intervals that enable better utilization of the
communication network. It is not possible to know ahead of time when such
commits take place.
is not supported in MySQL Cluster.
and transactions.
or columns, or, in cases where such
BLOB TEXT
and retry the entire transaction.
ROLLBACK
tables. If a
NDB
clause) is transactional. For tables containing a great
instead.
is not transactional when used on
LOAD DATA INFILE
When copying an
NDB
1526
ERROR 1296
NDBCLUSTER. In
InnoDB
TRUNCATE TABLE
DELETE FROM ...
statement, the engine
NDB
table as part of an
ALTER
that may roll
fails to
tables.
NDB
TABLE, the