SET

SET [GLOBAL] server_variable_name = value
SET [INDEX index_name] GLOBAL @user_variable_name = (int_val1 [, int_val2, ...])
SET NAMES value [COLLATE value]
SET @@dummy_variable = ignored_value

SET statement modifies a variable value. The variable names are case-insensitive. No variable value changes survive server restart.

SET NAMES statement and SET @@variable_name syntax, both introduced do nothing. They were implemented to maintain compatibility with 3rd party MySQL client libraries, connectors, and frameworks that may need to run this statement when connecting.

There are the following classes of the variables:

per-session server variable

global server variable

global user variable

global distributed variable

Global user variables are shared between concurrent sessions. Currently, the only supported value type is the list of BIGINTs, and these variables can only be used along with IN() for filtering purpose. The intended usage scenario is uploading huge lists of values to searchd (once) and reusing them (many times) later, saving on network overheads. Global user variables might be either transferred to all agents of distributed index or set locally in case of local index defined at distributed index. Example:

// in session 1
mysql> SET GLOBAL @myfilter=(2,3,5,7,11,13);
Query OK, 0 rows affected (0.00 sec)

// later in session 2
mysql> SELECT * FROM test1 WHERE group_id IN @myfilter;
+------+--------+----------+------------+-----------------+------+
| id   | weight | group_id | date_added | title           | tag  |
+------+--------+----------+------------+-----------------+------+
|    3 |      1 |        2 | 1299338153 | another doc     | 15   |
|    4 |      1 |        2 | 1299338153 | doc number four | 7,40 |
+------+--------+----------+------------+-----------------+------+
2 rows in set (0.02 sec)

Per-session and global server variables affect certain server settings in the respective scope. Known per-session server variables are:

AUTOCOMMIT = {0 | 1} Whether any data modification statement should be implicitly wrapped by BEGIN and COMMIT.

COLLATION_CONNECTION = collation_name Selects the collation to be used for ORDER BY or GROUP BY on string values in the subsequent queries. Refer to Collations for a list of known collation names.

CHARACTER_SET_RESULTS = charset_name Does nothing; a placeholder to support frameworks, clients, and connectors that attempt to automatically enforce a charset when connecting to a Manticore server.

SQL_AUTO_IS_NULL = value Does nothing; a placeholder to support frameworks, clients, and connectors that attempt to automatically enforce a charset when connecting to a Manticore server.

SQL_MODE = <value> Does nothing; a placeholder to support frameworks, clients, and connectors that attempt to automatically enforce a charset when connecting to a Manticore server.

WAIT_TIMEOUT = <value> Set connection timeout, either per session or global. Global can only be set on a VIP connection.

PROFILING = {0 | 1} Enables query profiling in the current session. Defaults to 0. See also show profile

MAX_THREADS_PER_QUERY = <POSITIVE_INT_VALUE> Redefines max_threads_per_query in the runtime. Per-session variable influences only the queries run in the same session (connection), i.e. up to disconnect. Value 0 means ‘no limit’. If both per-session and the global variables are set, the per-session one has a higher priority.

ro = {1 | 0} switch session to read-only mode or back. In show variables output the variable displayed with name session_read_only.

Known global server variables are:

QUERY_LOG_FORMAT = {plain | sphinxql} Changes the current log format.

LOG_LEVEL = {info | debug | replication | debugv |
debugvv}

Changes the current log verboseness level.

QCACHE_MAX_BYTES = <value> Changes the query_cache RAM use limit to a given value.

QCACHE_THRESH_MSEC = <value> Changes the query_cache> minimum wall time threshold to a given value.

QCACHE_TTL_SEC = <value> Changes the query_cache TTL for a cached result to a given value.

MAINTENANCE = {0 | 1} When set to 1, puts the server in maintenance mode. Only clients with vip connections can execute queries in this mode. All new non-vip incoming connections are refused. Existing connections are left intact.

GROUPING_IN_UTC = {0 | 1} When set to 1, cause timed grouping functions (day(), month(), year(), yearmonth(), yearmonthday()) to be calculated in utc. Read the doc for grouping_in_utc config params for more details.

QUERY_LOG_MIN_MSEC = <value> Changes the query_log_min_msec searchd settings value. In this case it expects value exactly in milliseconds and doesn’t parse time suffixes, as in config.

Warning This is very specific and ‘hard’ variable; filtered out messages will be just dropped and not written into the log at all. Better just filter your log with something like ‘grep’, in this case you’ll have at least full original log as backup.

LOG_DEBUG_FILTER = <string value> Filters out redundant log messages. If the value is set, then all logs with level > INFO (i.e., DEBUG, DEBUGV, etc.) will be compared with the string and output only in the case they starts with given value.

MAX_THREADS_PER_QUERY = <POSITIVE_INT_VALUE> Redefines max_threads_per_query in the runtime. As global it changes behaviour for all sessions. Value 0 means ‘no limit’. If both per-session and the global variables are set, the per-session one has a higher priority.

NET_WAIT = {-1 | 0 | POSITIVE_INT_VALUE} Changes the net_wait_tm searchd settings value.

IOSTATS = {0 | 1} Enable or disable I/O operations (except for attributes) reporting in query log.

CPUSTATS= {1|0} Turns on/off cpu time tracking.

COREDUMP= {1|0} Turns on/off saving a core file or a minidump of the server on crash. More details here.

PSEUDO_SHARDING = {1|0} Turns on/off search pseudo-sharding.

Examples:

mysql> SET autocommit=0;
Query OK, 0 rows affected (0.00 sec)

mysql> SET GLOBAL query_log_format=sphinxql;
Query OK, 0 rows affected (0.00 sec)

Setting variables online

SET