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https://dev.mysql.com/doc/refman/8.0/en/window-functions-frames.html
Frames are determined with respect to the current row, which enables a frame to move within a partition depending on the location of the current row within its partition. Examples: By defining a frame to be all rows from the partition start to the ... The definition of a window used with a window function can include a frame ...
https://dev.mysql.com/doc/refman/8.0/en/faqs-innodb-change-buffer.html
When should the change buffer be used? The change buffer is a feature designed to reduce random I/O to secondary indexes as indexes grow larger and no longer fit in the InnoDB buffer pool. How do I determine the current size of the change buffer? ...
https://dev.mysql.com/doc/refman/8.0/en/aggregate-functions.html
If you use an aggregate function in a statement containing no GROUP BY clause, it is equivalent to grouping on all rows. In MySQL 8.0, bit functions and operators permit binary string type arguments (BINARY, VARBINARY, and the BLOB types) and return ... This section describes aggregate functions that operate on sets of ...
https://dev.mysql.com/doc/refman/8.0/en/estimating-performance.html
For a 500,000-row table with a key value length of three bytes (the size of MEDIUMINT), the formula indicates log(500,000)/log(1024/3*2/(3+4)) + 1 = 4 seeks. To avoid this, increase the key cache size as the data grows. For small tables, you can ...
https://dev.mysql.com/doc/refman/8.0/en/subquery-materialization.html
Subquery materialization uses an in-memory temporary table when possible, falling back to on-disk storage if the table becomes too large. Either way, the row from t1 is not included in the query result. This indicates that, for a subquery that would ... The optimizer uses materialization to enable more efficient subquery ...
https://dev.mysql.com/doc/refman/8.0/en/information-functions.html
The intended use is from within the mysql client, which reports query execution times: mysql> SELECT BENCHMARK(1000000,AES_ENCRYPT('hello','goodbye')); +---------------------------------------------------+ | ...It may be used to time how quickly ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-deadlock-example.html
If client A attempts to update a row in Birds at the same time, this will lead to a deadlock: mysql> UPDATE Birds SET value=40 WHERE name='Buzzard'; ERROR 1213 (40001): Deadlock found when trying to get lock; try restarting transaction InnoDB rolls ... The following example illustrates how an error can occur when a lock request causes a ...
https://dev.mysql.com/doc/refman/8.0/en/load-xml.html
The tagname in the optional ROWS IDENTIFIED BY clause must also be given as a literal string, and must be surrounded by angle brackets (< and >). By default, the <row> element is considered to be the equivalent of a database table row; this can be ...LOAD XML acts as the complement of running the mysql client in XML output mode (that is, starting the client with the --xml ...
https://dev.mysql.com/doc/refman/8.0/en/hash-joins.html
Beginning with MySQL 8.0.18, join buffers for hash joins are allocated incrementally; thus, you can set join_buffer_size higher without small queries allocating very large amounts of RAM, but outer joins allocate the entire buffer. row ... By ...
https://dev.mysql.com/doc/refman/8.0/en/precision-math.html
For example, you can treat a value that is too large for a column as an error rather than having the value truncated to lie within the range of the column's data type. MySQL provides support for precision math: numeric value handling that results ...