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https://dev.mysql.com/doc/refman/9.7/en/innodb-locks-set.html
The locks are normally next-key locks that also block inserts into the “gap” immediately before the record. For example, in a UNION, scanned (and locked) rows from a table might be inserted into a temporary table before evaluating whether they ... A locking read, an UPDATE, or a DELETE generally set record locks on every index record that is scanned in the processing of an SQL ...
https://dev.mysql.com/doc/refman/9.7/en/innodb-tablespace-autoextend-size.html
By default, when a file-per-table or general tablespace requires additional space, the tablespace is extended incrementally according to the following rules: If the tablespace is less than an extent in size, it is extended one page at a time. If ...
https://dev.mysql.com/doc/refman/9.7/en/json-attribute-functions.html
The functions in this section return attributes of JSON values. An error occurs if the argument is not a valid JSON document. An empty array, empty object, or scalar value has depth 1. A nonempty array containing only elements of depth 1 or ...
https://dev.mysql.com/doc/refman/9.7/en/json.html
JSON documents stored in JSON columns are converted to an internal format that permits quick read access to document elements. The JSON_TYPE() function expects a JSON argument and attempts to parse it into a JSON value. One way to insert this as a ...The JSON data type provides these advantages over storing JSON-format strings in a string column: Automatic validation of JSON documents stored in JSON ...
https://dev.mysql.com/doc/refman/9.7/en/loop.html
Example: CREATE PROCEDURE doiterate(p1 INT) BEGIN label1: LOOP SET p1 = p1 + 1; IF p1 < 10 THEN ITERATE label1; END IF; LEAVE label1; END LOOP label1; SET @x = p1; END; . [begin_label:] LOOP statement_list END LOOP [end_label] LOOP implements a ...
https://dev.mysql.com/doc/refman/9.7/en/mathematical-functions.html
An implication of this is that ABS(-9223372036854775808) produces an error because the result cannot be stored in a signed BIGINT value. mysql> SELECT ABS(2); -> 2 mysql> SELECT ABS(-32); -> 32 This function is safe to use with BIGINT values. For ...
https://dev.mysql.com/doc/refman/9.7/en/monitor-innodb-mutex-waits-performance-schema.html
$> ./mysqlslap --auto-generate-sql --concurrency=100 --iterations=10 --number-of-queries=1000 --number-char-cols=6 --number-int-cols=6; Query the wait event data. A mutex is a synchronization mechanism used in the code to enforce that only one ...
https://dev.mysql.com/doc/refman/9.7/en/multiple-column-indexes.html
Note As an alternative to a composite index, you can introduce a column that is “hashed” based on information from other columns. MySQL can create composite indexes (that is, indexes on multiple columns). For certain data types, you can index a ...
https://dev.mysql.com/doc/refman/9.7/en/myisam-ftdump.html
Example: Suppose that the test database contains a table named mytexttable that has the following definition: CREATE TABLE mytexttable ( id INT NOT NULL, txt TEXT NOT NULL, PRIMARY KEY (id), FULLTEXT (txt) ) ENGINE=MyISAM; The index on id is index 0 ...It reads the MyISAM index file directly, so it must be run on the server host where the table is ...
https://dev.mysql.com/doc/refman/9.7/en/myisam-storage-engine.html
Table 18.2 MyISAM Storage Engine Features Feature Support B-tree indexes Yes Backup/point-in-time recovery (Implemented in the server, rather than in the storage engine.) Yes Cluster database support No Clustered indexes No Compressed data Yes ...