MySQL 8.0 Reference Manual Including MySQL NDB Cluster 8.0
The functions described in this section are used with GTID-based replication. It is important to keep in mind that all of these functions take string representations of GTID sets as arguments. As such, the GTID sets must always be quoted when used with them. See GTID Sets for more information.
The union of two GTID sets is simply their representations as strings, joined together with an interposed comma. In other words, you can define a very simple function for obtaining the union of two GTID sets, similar to that created here:
CREATE FUNCTION GTID_UNION(g1 TEXT, g2 TEXT) RETURNS TEXT DETERMINISTIC RETURN CONCAT(g1,',',g2);
For more information about GTIDs and how these GTID functions are used in practice, see Section 17.1.3, “Replication with Global Transaction Identifiers”.
Table 12.24 GTID Functions
Name | Description |
---|---|
GTID_SUBSET() |
Return true if all GTIDs in subset are also in set; otherwise false. |
GTID_SUBTRACT() |
Return all GTIDs in set that are not in subset. |
WAIT_FOR_EXECUTED_GTID_SET() |
Wait until the given GTIDs have executed on the replica. |
WAIT_UNTIL_SQL_THREAD_AFTER_GTIDS() (deprecated 8.0.18) |
Use WAIT_FOR_EXECUTED_GTID_SET() .
|
Given two sets of global transaction identifiers
set1
and
set2
, returns true if all GTIDs in
set1
are also in
set2
. Returns false otherwise.
The GTID sets used with this function are represented as strings, as shown in the following examples:
mysql>SELECT GTID_SUBSET('3E11FA47-71CA-11E1-9E33-C80AA9429562:23',
->'3E11FA47-71CA-11E1-9E33-C80AA9429562:21-57')\G
*************************** 1. row *************************** GTID_SUBSET('3E11FA47-71CA-11E1-9E33-C80AA9429562:23', '3E11FA47-71CA-11E1-9E33-C80AA9429562:21-57'): 1 1 row in set (0.00 sec) mysql>SELECT GTID_SUBSET('3E11FA47-71CA-11E1-9E33-C80AA9429562:23-25',
->'3E11FA47-71CA-11E1-9E33-C80AA9429562:21-57')\G
*************************** 1. row *************************** GTID_SUBSET('3E11FA47-71CA-11E1-9E33-C80AA9429562:23-25', '3E11FA47-71CA-11E1-9E33-C80AA9429562:21-57'): 1 1 row in set (0.00 sec) mysql>SELECT GTID_SUBSET('3E11FA47-71CA-11E1-9E33-C80AA9429562:20-25',
->'3E11FA47-71CA-11E1-9E33-C80AA9429562:21-57')\G
*************************** 1. row *************************** GTID_SUBSET('3E11FA47-71CA-11E1-9E33-C80AA9429562:20-25', '3E11FA47-71CA-11E1-9E33-C80AA9429562:21-57'): 0 1 row in set (0.00 sec)
Given two sets of global transaction identifiers
set1
and
set2
, returns only those GTIDs from
set1
that are not in
set2
.
All GTID sets used with this function are represented as strings and must be quoted, as shown in these examples:
mysql>SELECT GTID_SUBTRACT('3E11FA47-71CA-11E1-9E33-C80AA9429562:21-57',
->'3E11FA47-71CA-11E1-9E33-C80AA9429562:21')\G
*************************** 1. row *************************** GTID_SUBTRACT('3E11FA47-71CA-11E1-9E33-C80AA9429562:21-57', '3E11FA47-71CA-11E1-9E33-C80AA9429562:21'): 3e11fa47-71ca-11e1-9e33-c80aa9429562:22-57 1 row in set (0.00 sec) mysql>SELECT GTID_SUBTRACT('3E11FA47-71CA-11E1-9E33-C80AA9429562:21-57',
->'3E11FA47-71CA-11E1-9E33-C80AA9429562:20-25')\G
*************************** 1. row *************************** GTID_SUBTRACT('3E11FA47-71CA-11E1-9E33-C80AA9429562:21-57', '3E11FA47-71CA-11E1-9E33-C80AA9429562:20-25'): 3e11fa47-71ca-11e1-9e33-c80aa9429562:26-57 1 row in set (0.00 sec) mysql>SELECT GTID_SUBTRACT('3E11FA47-71CA-11E1-9E33-C80AA9429562:21-57',
->'3E11FA47-71CA-11E1-9E33-C80AA9429562:23-24')\G
*************************** 1. row *************************** GTID_SUBTRACT('3E11FA47-71CA-11E1-9E33-C80AA9429562:21-57', '3E11FA47-71CA-11E1-9E33-C80AA9429562:23-24'): 3e11fa47-71ca-11e1-9e33-c80aa9429562:21-22:25-57 1 row in set (0.01 sec)
WAIT_FOR_EXECUTED_GTID_SET(
gtid_set
[,
timeout
])
Wait until the server has applied all of the transactions
whose global transaction identifiers are contained in
gtid_set
; that is, until the
condition GTID_SUBSET(gtid_subset
,
@@GLOBAL.gtid_executed
) holds. See
Section 17.1.3.1, “GTID Format and Storage” for a definition
of GTID sets.
If a timeout is specified, and
timeout
seconds elapse before all
of the transactions in the GTID set have been applied, the
function stops waiting. timeout
is
optional, and the default timeout is 0 seconds, in which case
the function always waits until all of the transactions in the
GTID set have been applied.
WAIT_FOR_EXECUTED_GTID_SET()
monitors all
the GTIDs that are applied on the server, including
transactions that arrive from all replication channels and
user clients. It does not take into account whether
replication channels have been started or stopped.
For more information, see Section 17.1.3, “Replication with Global Transaction Identifiers”.
GTID sets used with this function are represented as strings and so must be quoted as shown in the following example:
mysql> SELECT WAIT_FOR_EXECUTED_GTID_SET('3E11FA47-71CA-11E1-9E33-C80AA9429562:1-5');
-> 0
For a syntax description for GTID sets, see Section 17.1.3.1, “GTID Format and Storage”.
For WAIT_FOR_EXECUTED_GTID_SET()
, the
return value is the state of the query, where 0 represents
success, and 1 represents timeout. Any other failures generate
an error.
gtid_mode
cannot be changed
to OFF while any client is using this function to wait for
GTIDs to be applied.
WAIT_UNTIL_SQL_THREAD_AFTER_GTIDS(
gtid_set
[,
timeout
][,channel
])
WAIT_UNTIL_SQL_THREAD_AFTER_GTIDS()
is
deprecated. Use
WAIT_FOR_EXECUTED_GTID_SET()
instead, which
works regardless of the replication channel or user client
through which the specified transactions arrive on the server.