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https://dev.mysql.com/doc/internals/en/select-structure.html
At the time of creating or performing any JOIN::* operation, LEX::current_select points to an appropriate SELECT_LEX. There are two structures that describe selects: st_select_lex (SELECT_LEX) for representing SELECT itself st_select_lex_unit ...
https://dev.mysql.com/doc/internals/en/select-subquery.html
The engine will be created at the time Item_subselect is constructed (Item_subselect::init method). In expressions, subqueries (that is, subselects) are represented by Item inherited from Item_subselect. To hide difference in performing single ...
https://dev.mysql.com/doc/internals/en/store-lock.html
Synopsis virtual THR_LOCK_DATA ** store_lock ( thd, to, lock_type); THD * thd ; THR_LOCK_DATA ** to ; enum thr_lock_type lock_type ; Description This is the store_lock method. The idea with handler::store_lock() is the following: The statement ...
https://dev.mysql.com/doc/internals/en/strings-directory.html
Many of the files in this subdirectory are equivalent to well-known functions that appear in most C string libraries. On the other hand, some of the files are MySQL additions or improvements. Often the MySQL changes are attempts to optimize the ...
https://dev.mysql.com/doc/internals/en/subtests.html
At least in cases where your file contains many subtests Mark these subtests for better readability of the script Write also a message into the protocol. And please explain what each subtest checks, unless it is obvious.
https://dev.mysql.com/doc/internals/en/tests-with-several-variants.html
Please think twice before you create engine-specific variants of a test or let runs with ps-protocol/sp-protocol/cursor-protocol/view-protocol happen. They might be of low value and a permanent wasting of resources and/or fail (protocol variants ...
https://dev.mysql.com/doc/internals/en/threads.html
Threads in mysqld can run at four different priorities, defined in mysql_priv.h: #define INTERRUPT_PRIOR 10 #define CONNECT_PRIOR 9 #define WAIT_PRIOR 8 #define QUERY_PRIOR 6 Some threads try to set their priority; others don't. These calls are ...
https://dev.mysql.com/doc/internals/en/too-greedy-test.html
Let's assume we have to check that every new created table causes a row in information_schema.tables. --replace_column 15 <CREATE_TIME> 16 <UPDATE_TIME> 17 <CHECK_TIME> SELECT * FROM information_schema.tables; The SELECT above makes the test ...It ...
https://dev.mysql.com/doc/internals/en/transactions-historical-note.html
MySQL would create a nested transaction at the start of each SQL statement, and destroy (commit or abort) the nested transaction at statement end. "Statement transaction" is a non-standard term that comes from the days when MySQL supported the ...
https://dev.mysql.com/doc/internals/en/transformation-scalar-in.html
To rewrite a scalar IN subquery, the Item_in_subselect::single_value_transformer method is used. The scalar IN subquery will be replaced with an Item_in_optimizer item. On a value request (one of val, val_int, or val_str methods) it evaluates the ...