Error
Error Code:
1878
MariaDB Error 1878: Temporary File Write Failure
Description
Error 1878, 'Temporary file write failure', indicates that MariaDB was unable to write data to a temporary file required for an ongoing operation. This typically occurs when the server's disk space is exhausted, file permissions are incorrect, or system resource limits have been reached, preventing MariaDB from completing tasks that rely on temporary storage.
Error Message
Temporary file write failure.
Known Causes
3 known causesInsufficient Disk Space
The server's disk partition where MariaDB stores temporary files is full or critically low on available space.
Incorrect File Permissions
The MariaDB user lacks the necessary write permissions for the directory designated for temporary files.
Operating System Limits
The operating system has reached its limit for open file descriptors or process memory, preventing new temporary files from being created.
Solutions
4 solutions available1. Increase Temporary Directory Space easy
Ensure the directory used for temporary files has sufficient free space.
1
Identify the temporary directory MariaDB is using. This is typically defined by the `tmpdir` system variable.
SHOW VARIABLES LIKE 'tmpdir';2
Check the available disk space on the filesystem where the `tmpdir` is located. Use a command like `df -h` on Linux/macOS or check drive properties in Windows Explorer.
df -h /path/to/your/tmpdir3
If space is low, free up disk space by deleting unnecessary files, or consider moving the `tmpdir` to a partition with more space.
4
If you change the `tmpdir` location, update the MariaDB configuration file (e.g., `my.cnf` or `my.ini`) and restart the MariaDB service.
[mysqld]
tmpdir = /new/path/to/tmpdir2. Adjust Temporary File Size Limits medium
Increase the maximum allowed size for temporary tables, especially for complex queries.
1
Check the current values of `tmp_table_size` and `max_heap_table_size`. These variables control the maximum size of in-memory temporary tables.
SHOW VARIABLES LIKE 'tmp_table_size';
SHOW VARIABLES LIKE 'max_heap_table_size';2
If these values are too low for your queries, increase them. A common starting point is to set them to a larger value, e.g., 1GB (1073741824 bytes).
SET GLOBAL tmp_table_size = 1073741824;
SET GLOBAL max_heap_table_size = 1073741824;3
To make these changes permanent, add or modify these settings in your MariaDB configuration file (e.g., `my.cnf` or `my.ini`) and restart the MariaDB service.
[mysqld]
tmp_table_size = 1073741824
max_heap_table_size = 10737418243. Verify File Permissions for Temporary Directory easy
Ensure the MariaDB user has read and write permissions to the temporary directory.
1
Identify the user under which the MariaDB server is running. This can often be found in the process list or in the MariaDB configuration file.
ps aux | grep mariadb2
Determine the `tmpdir` as shown in the first solution.
SHOW VARIABLES LIKE 'tmpdir';3
Check the permissions of the `tmpdir`. The MariaDB user needs read, write, and execute permissions.
ls -ld /path/to/your/tmpdir4
If permissions are incorrect, grant them to the MariaDB user. Replace `mariadb_user` with the actual user and `/path/to/your/tmpdir` with the correct directory.
sudo chown mariadb_user:mariadb_group /path/to/your/tmpdir
sudo chmod 755 /path/to/your/tmpdir4. Optimize or Rewrite Problematic Queries advanced
Address complex queries that may be generating excessively large temporary tables.
1
Enable the slow query log if it's not already enabled. This will log queries that exceed a certain execution time.
[mysqld]
log_slow_queries = /var/log/mysql/mysql-slow.log
long_query_time = 22
Analyze the slow query log to identify queries that are frequently failing or taking a long time. Tools like `mysqldumpslow` can be helpful.
mysqldumpslow /var/log/mysql/mysql-slow.log3
Use `EXPLAIN` on the problematic queries to understand their execution plans and identify areas for optimization (e.g., missing indexes, inefficient joins).
EXPLAIN SELECT ... FROM ... WHERE ...;4
Rewrite the queries to be more efficient, add necessary indexes, or consider breaking down complex operations into smaller, manageable steps.