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https://dev.mysql.com/doc/refman/8.4/en/performance-schema-variables-info-table.html
The variables_info table shows, for each system variable, the source from which it was most recently set, and its range of values. VARIABLE_SOURCE The source from which the variable was most recently set: COMMAND_LINE The variable was set on the ...
https://dev.mysql.com/doc/refman/8.4/en/problems-with-null.html
When using DISTINCT, GROUP BY, or ORDER BY, all NULL values are regarded as equal. When using ORDER BY, NULL values are presented first, or last if you specify DESC to sort in descending order. The concept of the NULL value is a common source of ...
https://dev.mysql.com/doc/refman/8.4/en/query-log.html
mysqld writes statements to the query log in the order that it receives them, which might differ from the order in which they are executed. This logging order is in contrast with that of the binary log, for which statements are written after they ...
https://dev.mysql.com/doc/refman/8.4/en/replication-features-limit.html
SELECT statements is unsafe since the order of the rows affected is not defined. (Such statements can be replicated correctly with statement-based replication only if they also contain an ORDER BY clause.) When such a statement is encountered: When ... Statement-based replication of LIMIT clauses in DELETE, UPDATE, and INSERT ...
https://dev.mysql.com/doc/refman/8.4/en/replication-features-transaction-inconsistencies.html
A gap in the externalized transaction set appears when, given an ordered sequence of transactions, a transaction that is later in the sequence is applied before some other transaction that is prior in the sequence. Binary logging and replica update ... Inconsistencies in the sequence of transactions that have been executed from the relay log can occur depending on your replication ...
https://dev.mysql.com/doc/refman/8.4/en/replication-gtids-concepts.html
The transaction_id is a sequence number determined by the order in which the transaction was committed on the source. This example shows the GTID set stored in the gtid_executed system variable (@@GLOBAL.gtid_executed) of a replica that has applied ... A global transaction identifier (GTID) is a unique identifier created and associated with each transaction committed on the server of origin (the ...
https://dev.mysql.com/doc/refman/8.4/en/replication-gtids-functions.html
Example 19.3 Selecting the most up-to-date replica for manual failover The stored function GTID_UNION() can be used to identify the most up-to-date replica from a set of replicas, in order to perform a manual failover operation after a source server ... This section provides examples of stored functions (see Chapter 27, Stored Objects) which you can create using some of the built-in functions provided by MySQL for use with GTID-based replication, listed here: GTID_SUBSET(): Shows whether one GTID set is a subset of ...
https://dev.mysql.com/doc/refman/8.4/en/replication-gtids-lifecycle.html
The replica verifies that no thread has yet taken ownership of the GTID in gtid_next in order to process the transaction. On a multithreaded replica (with replica_parallel_workers > 0), transactions can be applied in parallel, so replicated ... The ...
https://dev.mysql.com/doc/refman/8.4/en/replication-options-reference.html
replica_preserve_commit_order: Ensures that all commits by replica workers happen in same order as on source to maintain consistency when using parallel applier threads. slave_preserve_commit_order: Ensures that all commits by replica workers happen ... The following two sections provide basic information about the MySQL command-line options and system variables applicable to replication and the binary ...
https://dev.mysql.com/doc/refman/8.4/en/semijoins-antijoins.html
An ORDER BY clause is permitted but ignored, since ordering is irrelevant to the evaluation of semijoin strategies. A semijoin transformation can also be applied to a single-table UPDATE or DELETE statement that uses a [NOT] IN or [NOT] EXISTS ... A ...