EC
1979
MariaDBERRORCommonConfigurationHIGH confidence

Variable can only be set, not read

Production Risk

None — read is rejected; no data is exposed.

What this means

An attempt was made to read (SELECT @@variable) a system variable that is write-only. Some variables can be set but their value cannot be retrieved.

Why it happens
  1. 1SELECT @@old_passwords or reading another write-only system variable.
  2. 2Using SHOW VARIABLES for a variable that is not readable.
How to reproduce
trigger — this will error
trigger — this will error
SELECT @@old_passwords;

expected output

ERROR 1235 (HY000): Variable 'old_passwords' is a WRITE ONLY variable.

Fix

Do not read write-only variables; rely on configuration files instead

Do not read write-only variables; rely on configuration files instead
-- Check the value in my.cnf / my.ini or use SHOW VARIABLES LIKE 'variable_name'

Why this works

Write-only variables do not expose their value; use the configuration file as the source of truth.

Sources
Official documentation ↗

MySQL 8.0 — 1979 ER_VAR_CANT_BE_READ

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