How to use percona tool to add fields to MySQL table after interruption

Catalog

demand

programme

problem

Solution

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demand

Now there is a MySQL database , There are many tens of millions of large watches in the Library , Now we need to add fields to a large table with tens of millions of levels of data

programme

Because the amount of table data is too large , adopt MySQL It is not advisable to add fields directly from the client command line , because ： Modifying the table structure directly will lock the table , Because of the huge amount of data , Execution will be very slow , And it will affect the reading and writing of the table . Now most business systems , You need to make sure 7*24 Provide services hour after hour , Direct modification of large tables will lead to long-term table locking , Cause business interruption , Affect the business , This situation is definitely unacceptable .

So we need to find a feasible alternative , With , We use percona Tools for pt-online-change-schema Add field , This tool can modify the table structure with little impact on performance .

problem

Use pt-online-change-schema The process of adding fields is interrupted due to the connection , Adding fields failed , We re-use the tool to add fields, and the result is an error , The error information is as follows ：

This error indicates that the trigger already exists .

analysis

We know how to use pt-online-change-schema Tools to give MySQL Adding fields to the table of will create three triggers （insert、update、delete）, So we need to delete these three triggers before using the tool to add fields to the table .

Solution

1. Query triggers

select * from information_schema.triggers;

2. Delete trigger

Find the corresponding TRIGGER_SCHEMA and TRIGGER_NAME, such as

drop trigger test.pt_osc_test_t_tab1_ins;

drop trigger test.pt_osc_test_t_tab1_upd;

drop trigger test.pt_osc_test_t_tab1_del;

3. Reuse pt-online-change-schema Add fields when the tool executes .