schemadiff: ALTER TABLE is not INSTANT-able if adding column with default expression value

[shlomi-noach]

Description

Fixes #16024

Although not documented in https://dev.mysql.com/doc/refman/8.0/en/innodb-online-ddl-operations.html, adding a column with a default expression (non-literal) value is not eligible for INSTANT DDL:

> alter table tt add column i3 int default (2+5), algorithm=instant;
ERROR 1845 (0A000): ALGORITHM=INSTANT is not supported for this operation. Try ALGORITHM=COPY/INPLACE.

vs

> alter table tt add column i3 int default 2, algorithm=instant;
Query OK, 0 rows affected (0.00 sec)

This PR makes schemadiff aware of said limitation.

Related Issue(s)

• Bug Report: schemadiff should not allow INSTANT DDL when setting expression-based default column value #16024
• Feature request: schemadiff to be aware and knowledgeable about INSTANT-capable changes #14877

Checklist

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.23%. Comparing base (0a86449) to head (0da2cfb).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16028      +/-   ##
==========================================
- Coverage   68.23%   68.23%   -0.01%     
==========================================
  Files        1541     1541              
  Lines      197115   197117       +2     
==========================================
- Hits       134503   134499       -4     
- Misses      62612    62618       +6     

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