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Implementation of MDEV-28 LIMIT ROWS EXAMINED

Browse Source 
https://mariadb.atlassian.net/browse/MDEV-28
  
This task implements a new clause LIMIT ROWS EXAMINED <num>
as an extention to the ANSI LIMIT clause. This extension
allows to limit the number of rows and/or keys a query
would access (read and/or write) during query execution.
This commit is contained in:
unknown
2012-03-11 14:39:20 +02:00
parent f92cfdb8a9
commit 8aebd44e0e
17 changed files with 1635 additions and 53 deletions
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44
sql/sql_class.h
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@@ -365,7 +365,10 @@ public:
};
/* Note: these states are actually bit coded with HARD */
/**
These states are bit coded with HARD. For each state there must be a pair
<state_even_num>, and <state_odd_num>_HARD.
*/
enum killed_state
{
NOT_KILLED= 0,
@@ -375,15 +378,23 @@ enum killed_state
KILL_QUERY= 4,
KILL_QUERY_HARD= 5,
/*
All of the following killed states will kill the connection
KILL_CONNECTION must be the first of these!
ABORT_QUERY signals to the query processor to stop execution ASAP without
issuing an error. Instead a warning is issued, and when possible a partial
query result is returned to the client.
*/
KILL_CONNECTION= 6,
KILL_CONNECTION_HARD= 7,
KILL_SYSTEM_THREAD= 8,
KILL_SYSTEM_THREAD_HARD= 9,
KILL_SERVER= 10,
KILL_SERVER_HARD= 11
ABORT_QUERY= 6,
ABORT_QUERY_HARD= 7,
/*
All of the following killed states will kill the connection
KILL_CONNECTION must be the first of these and it must start with
an even number (becasue of HARD bit)!
*/
KILL_CONNECTION= 8,
KILL_CONNECTION_HARD= 9,
KILL_SYSTEM_THREAD= 10,
KILL_SYSTEM_THREAD_HARD= 11,
KILL_SERVER= 12,
KILL_SERVER_HARD= 13
};
extern int killed_errno(killed_state killed);
@@ -1951,6 +1962,20 @@ public:
filesort() before reading it for e.g. update.
*/
ha_rows examined_row_count;
/**
The number of rows and/or keys examined by the query, both read,
changed or written.
*/
ulonglong accessed_rows_and_keys;
/**
Check if the number of rows accessed by a statement exceeded
LIMIT ROWS EXAMINED. If so, signal the query engine to stop execution.
*/
void check_limit_rows_examined()
{
if (++accessed_rows_and_keys > lex->limit_rows_examined_cnt)
killed= ABORT_QUERY;
}
USER_CONN *user_connect;
CHARSET_INFO *db_charset;
@@ -3643,6 +3668,7 @@ void mark_transaction_to_rollback(THD *thd, bool all);
inline void handler::increment_statistics(ulong SSV::*offset) const
{
status_var_increment(table->in_use->status_var.*offset);
table->in_use->check_limit_rows_examined();
}
inline void handler::decrement_statistics(ulong SSV::*offset) const