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MXS-3143: Route FOUND_ROWS to last used target

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This will cause the query to be routed to the same server where a possible
SQL_CALC_FOUND_ROWS was executed.
This commit is contained in:
Markus Mäkelä
2020-08-28 11:43:39 +03:00
parent 24d6a582c2
commit ebdb9655e6
2 changed files with 28 additions and 0 deletions
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13
Documentation/Routers/ReadWriteSplit.md
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@ -643,3 +643,16 @@ executed session command for the duration of the session. Applications that use
long-running sessions might cause MariaDB MaxScale to consume a growing amount
of memory unless the sessions are closed. This can be solved by adjusting the
value of `max_sescmd_history`.
### Routing to previous target
In the following cases, a query is routed to the same server where the previous
query was executed. If no previous target is found, the query is routed to the
current master.
* If a query uses the `FOUND_ROWS()` function, it will be routed to the server
where the last query was executed. This is done with the assumption that a
query with `SQL_CALC_FOUND_ROWS` was previously executed.
* COM_STMT_FETCH_ROWS will always be routed to the same server where the
COM_STMT_EXECUTE was routed.

15
server/core/queryclassifier.cc
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@ -1107,6 +1107,21 @@ QueryClassifier::RouteInfo QueryClassifier::update_route_info(
process_routing_hints(pBuffer->hint, &route_target);
if (route_target == TARGET_SLAVE)
{
const QC_FUNCTION_INFO* infos = nullptr;
size_t n_infos = 0;
qc_get_function_info(pBuffer, &infos, &n_infos);
for (size_t i = 0; i < n_infos; ++i)
{
if (strcasecmp(infos[i].name, "FOUND_ROWS") == 0)
{
route_target = TARGET_LAST_USED;
}
}
}
if (session_trx_is_ending(m_pSession)
|| qc_query_is_type(type_mask, QUERY_TYPE_BEGIN_TRX))
{