the actual values in the index. For example, if you select all values greater than 10 for update, a gap lock prevents another transaction from inserting a new value that is greater than 10. The supremum record  and infimum record  represent the gaps containing all values greater than or less than all the current index values. See Also concurrency, gap lock, index, infimum record, isolation level, supremum record. 

## gap lock 

 A lock  on a gap  between index records, or a lock on the gap before the first or after the last index record. For example, SELECT c1 FROM t WHERE c1 BETWEEN 10 and 20 FOR UPDATE;  prevents other transactions from inserting a value of 15 into the column t.c1 , whether or not there was already any such value in the column, because the gaps between all existing values in the range are locked. Contrast with record lock  and next-key lock . 

Gap locks are part of the tradeoff between performance and concurrency , and are used in some transaction isolation levels  and not others. See Also gap, infimum record, lock, next-key lock, record lock, supremum record. 

## general log 

See general query log. 

## general query log 

 A type of log  used for diagnosis and troubleshooting of SQL statements processed by the MySQL server. Can be stored in a file or in a database table. You must enable this feature through the general_log  configuration option to use it. You can disable it for a specific connection through the sql_log_off  configuration option. 

Records a broader range of queries than the slow query log . Unlike the binary log , which is used for replication, the general query log contains SELECT  statements and does not maintain strict ordering. For more information, see Section 5.4.3, “The General Query Log” . See Also binary log, log, slow query log. 

## general tablespace 

 A shared InnoDB tablespace  created using CREATE TABLESPACE  syntax. General tablespaces can be created outside of the MySQL data directory, are capable of holding multiple tables , and support tables of all row formats. General tablespaces were introduced in MySQL 5.7.6. 

Tables are added to a general tablespace using CREATE TABLE tbl_name  ... TABLESPACE [=] tablespace_name  or ALTER TABLE tbl_name  TABLESPACE [=] tablespace_name  syntax. 

Contrast with system tablespace  and file-per-table  tablespace. 

For more information, see Section 15.6.3.3, “General Tablespaces” . See Also file-per-table, system tablespace, table, tablespace. 

## generated column 

 A column whose values are computed from an expression included in the column definition. A generated column can be virtual  or stored . See Also base column, stored generated column, virtual generated column. 

## generated stored column 

See stored generated column. 

## generated virtual column 

See virtual generated column. 

## Glassfish 

See Also J2EE. 

