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https://dev.mysql.com/doc/refman/5.7/en/slow-query-log.html
The slow query log consists of SQL statements that take more than long_query_time seconds to execute and require at least min_examined_row_limit rows to be examined. If the slow query log is enabled and FILE is selected as an output destination, ...
https://dev.mysql.com/doc/refman/5.7/en/nested-loop-joins.html
MySQL executes joins between tables using a nested-loop algorithm or variations on it. Nested-Loop Join Algorithm Block Nested-Loop Join Algorithm Nested-Loop Join Algorithm A simple nested-loop join (NLJ) algorithm reads rows from the first table ...For example, if 10 rows are read into a buffer and the buffer is passed to the next inner loop, each row read in the inner loop can be compared against all 10 rows in the ...
https://dev.mysql.com/doc/refman/5.7/en/replication-mode-change-online-concepts.html
When using GTIDs you can take advantage of auto-positioning and automatic fail-over, as well as use WAIT_FOR_EXECUTED_GTID_SET(), session_track_gtids, and monitor replicated transactions using Performance Schema tables. The valid values for ... To ...
https://dev.mysql.com/doc/refman/5.7/en/sys-statement-analysis.html
max_latency The maximum single wait time of timed occurrences of the statement. err_count The total number of errors produced by occurrences of the statement. total_latency The total wait time of timed occurrences of the statement. avg_latency The ...The statement_analysis and x$statement_analysis views have these columns: query The normalized statement ...
https://dev.mysql.com/doc/refman/5.7/en/data-size.html
Smaller tables normally require less main memory while their contents are being actively processed during query execution. With ROW_FORMAT=REDUNDANT, CHAR(N) occupies N × the maximum byte length of the character set. With the compact family of rows ... Design your tables to minimize their space on the ...
https://dev.mysql.com/doc/refman/5.7/en/replication-features-functions.html
(You can consider the function execution timestamp and random number seed as implicit inputs that are identical on the source and replica.) The FOUND_ROWS() and ROW_COUNT() functions are not replicated reliably using statement-based replication. To ... Certain functions do not replicate well under some conditions: The USER(), CURRENT_USER() (or CURRENT_USER), UUID(), VERSION(), and LOAD_FILE() functions are replicated without change and thus do not work reliably on the replica unless row-based replication is ...
https://dev.mysql.com/doc/refman/5.7/en/sql-prepared-statements.html
Using prepared statements with placeholders for parameter values has the following benefits: Less overhead for parsing the statement each time it is executed. You can use it from any program that can send SQL statements to the server to be executed, ...Typically, database applications process large volumes of almost-identical statements, with only changes to literal or variable values in clauses such as WHERE for queries and deletes, SET for updates, and VALUES for ...
https://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-programs-ndb-drop-table.html
--connect-retries Command-Line Format --connect-retries=# Type Integer Default Value 12 Minimum Value 0 Maximum Value 12 Number of times to retry connection before giving up. --connect-retry-delay Command-Line Format --connect-retry-delay=# Type ...
https://dev.mysql.com/doc/refman/5.7/en/query-cache-configuration.html
In this case, the server does not acquire the query cache mutex at all, which means that the query cache cannot be enabled at runtime and there is reduced overhead in query execution. Note You can set the maximum size that can be specified for the ...For example, a client can disable use of the query cache for its own queries like this: mysql> SET SESSION query_cache_type = OFF; If you set query_cache_type at server startup (rather than at runtime with a SET statement), only the numeric values are ...
https://dev.mysql.com/doc/refman/5.7/en/performance-schema-status-monitoring.html
If the value chosen for performance_schema_max_mutex_classes is too small, no error is reported in the error log and there is no failure at runtime. For example, if a mutex is instrumented in the server source but the server cannot allocate memory ...Names for these variables have several forms: Performance_schema_xxx_classes_lost indicates how many instruments of type xxx could not be ...