Bug Report: schemadiff should not allow INSTANT DDL when setting expression-based default column value

[shlomi-noach]

Overview of the Issue

Although not mentioned in the MySQL docs, the following is not an INSTANT-able operation:

> alter table t add column i int default ((2+5)), algorithm=instant;
ERROR 1845 (0A000): ALGORITHM=INSTANT is not supported for this operation. Try ALGORITHM=COPY/INPLACE.

MySQL will not accept an expression-based default value with INSTANT algorithm.

Context: #14877

Reproduction Steps

Binary Version

v19

Operating System and Environment details

-

Log Fragments

No response

[shlomi-noach]

Note: alter table t modify column i1 int default ((2+5)), algorithm=instant; works for an existing column. The problem is with adding a new columns.