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https://dev.mysql.com/doc/refman/8.4/en/perl-support.html
You can obtain the necessary modules from http://search.cpan.org for Unix, or by using the ActiveState ppm program on Windows. The Perl DBI module provides a generic interface for database access. You can write a DBI script that works with many ...
https://dev.mysql.com/doc/refman/8.4/en/problems-with-null.html
All columns in the following example return NULL: mysql> SELECT NULL, 1+NULL, CONCAT('Invisible',NULL); To search for column values that are NULL, you cannot use an expr = NULL test. The exception to this is COUNT(*), which counts rows and not ...
https://dev.mysql.com/doc/refman/8.4/en/replication-options-gtids.html
binlog_gtid_simple_recovery Command-Line Format --binlog-gtid-simple-recovery[={OFF|ON}] System Variable binlog_gtid_simple_recovery Scope Global Dynamic No SET_VAR Hint Applies No Type Boolean Default Value ON This variable controls how binary log ... The MySQL Server system variables described in this section are used to monitor and control Global Transaction Identifiers ...
https://dev.mysql.com/doc/refman/8.4/en/replication-options-reference.html
Slave_rows_last_search_algorithm_used: Search algorithm most recently used by this replica to locate rows for row-based replication (index, table, or hash scan). gtid_executed_compression_period: Compress gtid_executed table each time this many ...
https://dev.mysql.com/doc/refman/8.4/en/selinux-troubleshooting.html
This issue can occur if MySQL is configured to read from or write to a non-default directory or file. In this case, a “denial” message is logged to /var/log/audit/audit.log: $> grep "denied" /var/log/audit/audit.log type=AVC ... Troubleshooting ...
https://dev.mysql.com/doc/refman/8.4/en/semijoins-antijoins.html
This occurs due to heuristic pruning during greedy search, which can be avoided by setting optimizer_prune_level=0. The optimizer uses semijoin strategies to improve subquery execution, as described in this section. To list the classes that actually ... A semijoin is a preparation-time transformation that enables multiple execution strategies such as table pullout, duplicate weedout, first match, loose scan, and ...
https://dev.mysql.com/doc/refman/8.4/en/set.html
A consequence of this is that SET member values should not themselves contain commas. For example, you can retrieve numeric values from a SET column like this: mysql> SELECT set_col+0 FROM tbl_name; If a number is stored into a SET column, the bits ... A SET is a string object that can have zero or more values, each of which must be chosen from a list of permitted values specified when the table is ...
https://dev.mysql.com/doc/refman/8.4/en/sorted-index-builds.html
The drawbacks of this “top-down” method of building an index are the cost of searching for an insert position and the constant splitting and merging of B-tree nodes. This method of index creation is also known as a sorted index build. In the ...
https://dev.mysql.com/doc/refman/8.4/en/spatial-geohash-functions.html
The functions in this section enable manipulation of geohash values, which provides applications the capabilities of importing and exporting geohash data, and of indexing and searching geohash values. Unless otherwise specified, functions in this ...
https://dev.mysql.com/doc/refman/8.4/en/storage-engines.html
NDB (also known as NDBCLUSTER): This clustered database engine is particularly suited for applications that require the highest possible degree of uptime and availability. Example: This engine serves as an example in the MySQL source code that ...