02-20-2019
Quote:
Originally Posted by
figaro
I have a big, ugly query which is quadratic in the input size and therefore want to display an approximate completion time prior to sending it off:
I don't see the link between what you want and the query and like you have said it's not correct. So, to analyze the query you have the explain command to get information about the plan that will be used and from there you can estimate quick query and slow query.
See the official web site for "EXPLAIN"
The other option is to do it on the application side.
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LEARN ABOUT PHP
mysqlnd_ms_query_is_select
MYSQLND_MS_QUERY_IS_SELECT(3) 1 MYSQLND_MS_QUERY_IS_SELECT(3)
mysqlnd_ms_query_is_select - Find whether to send the query to the master, the slave or the last used MySQL server
SYNOPSIS
int mysqlnd_ms_query_is_select (string $query)
DESCRIPTION
Finds whether to send the query to the master, the slave or the last used MySQL server.
The plugins built-in read/write split mechanism will be used to analyze the query string to make a recommendation where to send the query.
The built-in read/write split mechanism is very basic and simple. The plugin will recommend sending all queries to the MySQL replication
master server but those which begin with SELECT, or begin with a SQL hint which enforces sending the query to a slave server. Due to the
basic but fast algorithm the plugin may propose to run some read-only statements such as SHOW TABLES on the replication master.
PARAMETERS
o $query
- Query string to test.
RETURN VALUES
A return value of MYSQLND_MS_QUERY_USE_MASTER indicates that the query should be send to the MySQL replication master server. The function
returns a value of MYSQLND_MS_QUERY_USE_SLAVE if the query can be run on a slave because it is considered read-only. A value of
MYSQLND_MS_QUERY_USE_LAST_USED is returned to recommend running the query on the last used server. This can either be a MySQL replication
master server or a MySQL replication slave server.
If read write splitting has been disabled by setting mysqlnd_ms.disable_rw_split, the function will always return
MYSQLND_MS_QUERY_USE_MASTER or MYSQLND_MS_QUERY_USE_LAST_USED.
EXAMPLES
Example #1
mysqlnd_ms_query_is_select(3) example
<?php
function is_select($query)
{
switch (mysqlnd_ms_query_is_select($query))
{
case MYSQLND_MS_QUERY_USE_MASTER:
printf("'%s' should be run on the master.
", $query);
break;
case MYSQLND_MS_QUERY_USE_SLAVE:
printf("'%s' should be run on a slave.
", $query);
break;
case MYSQLND_MS_QUERY_USE_LAST_USED:
printf("'%s' should be run on the server that has run the previous query
", $query);
break;
default:
printf("No suggestion where to run the '%s', fallback to master recommended
", $query);
break;
}
}
is_select("INSERT INTO test(id) VALUES (1)");
is_select("SELECT 1 FROM DUAL");
is_select("/*" . MYSQLND_MS_LAST_USED_SWITCH . "*/SELECT 2 FROM DUAL");
?>
The above example will output:
INSERT INTO test(id) VALUES (1) should be run on the master.
SELECT 1 FROM DUAL should be run on a slave.
/*ms=last_used*/SELECT 2 FROM DUAL should be run on the server that has run the previous query
SEE ALSO
Predefined Constants, user filter .Runtime configuration, mysqlnd_ms.disable_rw_split, mysqlnd_ms.enable.
PHP Documentation Group MYSQLND_MS_QUERY_IS_SELECT(3)