MDEV-40122: +DEFAULT is not a valid value for master_heartbeat_period

[prathamesh04]

Summary

CHANGE MASTER TO master_heartbeat_period= +DEFAULT; was accepted as valid syntax (equivalent to = DEFAULT). It now produces a syntax error again.

This is a mismerge of MDEV-38454 into MDEV-28302:

• MDEV-28302 changed the rule to MASTER_HEARTBEAT_PERIOD_SYM '=' num_or_default, adding DEFAULT support.
• MDEV-38454 added opt_plus (to allow values like +60) on top of it, resulting in opt_plus num_or_default, which also accepts +DEFAULT.

Fix

Split the grammar rule in sql/sql_yacc.yy so opt_plus may only precede a numeric literal:

• MASTER_HEARTBEAT_PERIOD_SYM '=' opt_plus NUM_literal (numbers, with or without +)
• MASTER_HEARTBEAT_PERIOD_SYM '=' DEFAULT

master_heartbeat_period= +45 and = DEFAULT still work; +DEFAULT is rejected with ER_PARSE_ERROR.

Note: 11.4 and 11.8 use opt_plus NUM_literal (no DEFAULT at all), so they are not affected; the bug only exists on the 12.x line.

Test

Extended mysql-test/main/change_master_default.test (the MDEV-28302 test) with a regression case for +DEFAULT plus positive checks for +45 and DEFAULT. Verified with:

./mariadb-test-run.pl --suite=main change_master_default ps_change_master

Both tests pass (the generated parser is rebuilt from sql_yacc.yy at build time).

Jira: https://jira.mariadb.org/browse/MDEV-40122

This contribution is licensed under the 3-clause BSD license.

[CLAassistant]

All committers have signed the CLA.

[prathamesh04]

Hi @LinuxJedi, could you please take a look? This is a small parser fix for MDEV-40122, a mismerge of MDEV-38454 into MDEV-28302, with a regression test in main.change_master_default. Thanks!

[ParadoxV5]

I’m quite certain that LinuxJedi doesn’t work at MariaDB anymore.

[vuvova]

Agree. Why should +DEFAULT work? Logically, the syntax can be either

• value literal
• DEFAULT keyword
• expression

It seems that master_heartbeat_period accepts the first two, a literal number and a DEFAULT keyword. It doesn't support expressions. +5 is still a literal number, so must be recognized. But +DEFAULT is neither, not a number, not a DEFAULT, it's not even a valid expression. It's a syntactically incorrect from any point of view and it's not supported anywhere (except in INSERT where both expressions are supported and DEFAULT is a valid expression)

[gkodinov]

Thank you for your contribution! This is a preliminary review.

LGTM. Please stand by for the final review.

[gkodinov]

LGTM. Please keep working with the final reviewer.