message size in DD table INNODB_REPLICATION_LOG is too small

[Joe Daly]

in replication_dictionary.cc

add_field("TRANSACTION_MESSAGE_STRING", plugin::TableFunction::STRING, 2048, false);
add_field("TRANSACTION_MESSAGE_BINARY", plugin::TableFunction::VARBINARY, 2048, false);

these should be based on the gpb message size sys_var

[Andrew Hutchings (linuxjedi)]

I assume by "gpb message size" you mean transaction-message-threshold? If so, here is the thing, that variable is a session level variable but you are outputting data from a global scope. So do we use the session level variable or the global level? Both could truncate messages based on user settings.

[David Shrewsbury (dshrews)]

--transaction-message-threshold should not be settable at the session level. This is a bug and could cause all sorts of chaos.

[Joe Daly (skinny.moey)]

If --transaction-message-threshold was made global in scope and read only (settable at startup only) that should solve the problem of what size to make the DD field. The message threshold has low limits so I dont see a need to truncate at all.

[Andrew Hutchings (linuxjedi)]

Can't merge my branch until bug #646898 is fixed. Transaction log table takes up too much RAM for our slicehost boxes with it in.

Put on 'In Progress' until bug #646898 is fixed.

[Andrew Hutchings (linuxjedi)]

So, new plan:

Expose internal SYS_REPLICATION_LOG table for the binary data and use the DD just for string representation of the data. This also fixes several other problems and will greatly improve performance accessing the binary data.