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https://dev.mysql.com/doc/internals/en/memory-allocation-mysql-server.html
Things in libraries that are outside of MySQL's control (like hash tables). Some objects have their own MEMROOT: TABLE TABLE_SHARE Query_arena st_transactions . The basic logic to use: All things that are used only for the duration of a query are ...
https://dev.mysql.com/doc/internals/en/multi-resultset.html
01 31 00 0c 3f 00 01 00 00 00 08 81 00 00 00 00 .1..?........... 05 00 00 03 fe 00 00 0a 00 02 00 00 04 01 31 05 ..............1. see the EOF_Packet: 05 00 00 03 fe 00 00 0a 00 with its status-flag being 0a the 2nd resultset: 01 00 00 06 01 17 00 00 ...
https://dev.mysql.com/doc/internals/en/negative-tests.html
String longer than column Limited number of tables, columns, variables, ... Maximum - 1, Maximum, Maximum + 1 Assume an SQL operation that affects the filesystem (LOAD DATA, CREATE SCHEMA or TABLE, backup/restore, ...). A "negative" test is a test ...
https://dev.mysql.com/doc/internals/en/optimizer-code.html
*/ optimize_cond() opt_sum_query() make_join_statistics() get_quick_record_count() choose_plan() /* Find the best way to access tables */ /* as specified by the user. The make_join_statistics() routine puts together all the information it can find ... This diagram shows the structure of the function handle_select() in /sql/sql_select.cc (the server code that handles a query): handle_select() mysql_select() JOIN::prepare() setup_fields() JOIN::optimize() /* optimizer is from here ...
https://dev.mysql.com/doc/internals/en/optimizer-eliminating-dead-code.html
SELECT * FROM Table1 WHERE column1 = 'Canada'; The optimizer will not eliminate the condition in the query, even though the CREATE TABLE definition makes it an impossible condition. A transformation takes place for conditions that are always true, ...
https://dev.mysql.com/doc/internals/en/select-special-engines.html
The normal engine can be replaced with such special engines only during the optimization process.
https://dev.mysql.com/doc/internals/en/sleep.html
Example: --connection conn1 LOCK TABLE t1 WRITE; --connection conn2 # This will block in wait_for_lock(). FLUSH TABLE t1; The BIG, BIG problem with 'sleep' is that you need to specify a fixed time. In some cases race conditions can be repeated when ...
https://dev.mysql.com/doc/internals/en/threads.html
Like the old "sync" daemon in unix, this thread occasionally flushes MyISAM tables to disk. 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 ...
https://dev.mysql.com/doc/internals/en/user-level-locks.html
LOCK TABLE t1 IN SHARE MODE; --connection conn2 # Acquire the user level lock "mysqltest1". User-level locks are controlled with the SQL functions GET_LOCK(str,timeout) IS_FREE_LOCK(str) IS_USED_LOCK(str) RELEASE_LOCK(str) They can be used at ...
https://dev.mysql.com/doc/internals/en/wait-condition.html
Example: --connection conn1 LOCK TABLE t1 WRITE; --connection conn2 # Get the id of this thread. FLUSH TABLE t1; In conn2 we get the thread ID first. Like 'sleep', this method can also be used, when all but one thread reach a blocked state. If you ...