Monty Taylor wrote:
Brian Aker wrote:
Hi!
What is the value of CHECKSUM TABLE? Should this have been done as an
I_S feature?
I was looking through the bug reports and it looks to give out fairly
inconsistent, and sometimes wrong, answers. Is this being used in
production?
It isn't - or shouldn't be. BUT - if it actually worked well, like
Baron's checksumming thing from maatkit - then it would be a good thing
for many people, I imagine.
My plan was to rip the current implementation out, as it is specific
only to MyISAM, and replace with a storage-engine agnostic CHECKSUM
command, taking the form:
CHECKSUM (ALL | TABLE table_identifier | TABLES table_list);
with the ALL representing all tables in the server.
This CHECKSUM command would be able to be manually run on a publisher
server (a master in MySQL world) and whenever the command hit a
subscriber (slave), the subscriber would checksum itself and, depending
on an option set up in the configuration file, would either:
a) Abort replication immediately and stop subscriber feed
b) Continue replication but provide an email or warning of some kind
The Google Protobuffer message format I will propose is as follows:
message Checksum
{
required uint32 checksum; /* crc32 value */
repeated string table; /* contains table_list or table_identifier */
}
The Command message will be modified as follows:
message Command
{
...
optional Checksum checksum_record; /* A CHECKSUM SQL command result */
}
NOTE: There is no need for a timestamp in the Checksum message, as it is
already available in the Command message, of which Checksum is an
encapsulted sub-message.
This CHECKSUM command is in addition to the existing CRC32 checksum that
the command log already keeps for its segments.
Thoughts?
Jay
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