Implement check if php serialize_precision is properly set to prevent huge matomo_archive_blob-tables

[rr-it]

Summary

The php serialize_precision ini setting directly influences the BLOB size and thereby the size of matomo_archive_blob-tables.

E.g. serialize_precision=100 results in:

php -r 'echo serialize((float)0.402);'
d:0.40200000000000002398081733190338127315044403076171875;

With a setting like this the matomo_archive_blob-tables really become very huge.

Default setting serialize_precision=-1 results in:

php -r 'echo serialize((float)0.402);'
d:0.402;

Also see:
https://www.php.net/manual/en/ini.core.php#ini.serialize-precision

Since PHP 7.1 the default is serialize_precision=-1.

-1 means that an enhanced algorithm for rounding such numbers will be used.

For PHP versions < 7.1 the default is serialize_precision=17 .

Your Environment

• Matomo Version:
• PHP Version:
• Server Operating System:
• Additionally installed plugins:

[MatomoForumNotifications]

This issue has been mentioned on Matomo forums. There might be relevant details there:

https://forum.matomo.org/t/reduce-size-of-archive-tables-blob-use-proper-php-ini-serialize-precision-1/62694/1