Oracle 5.0 Reference Manual page 1339

the master host a "dummy" slave process whose default storage engine is BLACKHOLE, depicted as
follows:
The master writes to its binary log. The "dummy"
combination of
replicate-do-*
log of its own. (See Section 16.1.2, "Replication and Binary Logging Options and
filtered log is provided to the slave.
The dummy process does not actually store any data, so there is little processing overhead incurred
by running the additional
repeated with additional replication slaves.
triggers for
INSERT BLACKHOLE
does not actually store any data,
clause in the trigger definition does not apply because there are no rows.
Other possible uses for the
• Verification of dump file syntax.
• Measurement of the overhead from binary logging, by comparing performance using
with and without binary logging enabled.
• is essentially a "no-op" storage engine, so it could be used for finding performance
BLACKHOLE
bottlenecks not related to the storage engine itself.
Blackhole Engine and Auto Increment Columns
The Blackhole engine is a no-op engine. Any operations performed on a table using Blackhole will have
no effect. This should be born in mind when considering the behavior of primary key columns that auto
increment. The engine will not automatically increment field values, and does not retain auto increment
field state. This has important implications in replication.
Consider the following replication scenario where all three of the following conditions apply:
1. On a master server there is a blackhole table with an auto increment field that is a primary key.
2. On a slave the same table exists but using the MyISAM engine.
3. Inserts are performed into the master's table without explicitly setting the auto increment value in
the statement itself or through using a
INSERT
In this scenario replication will fail with a duplicate entry error on the primary key column.
The Storage Engine
BLACKHOLE
and
replicate-ignore-*
process on the replication master host. This type of setup can be
mysqld
tables work as expected. However, because the
and
UPDATE DELETE
storage engine include:
BLACKHOLE
1319
process acts as a slave, applying the desired
mysqld
rules, and writes a new, filtered binary
triggers are not activated: The
statement.
SET INSERT_ID
Variables".) This
table
BLACKHOLE
FOR EACH ROW
BLACKHOLE