From ebdb9655e623a615d32cb488da8c9add599b78ef Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Markus=20M=C3=A4kel=C3=A4?= Date: Fri, 28 Aug 2020 11:43:39 +0300 Subject: [PATCH] MXS-3143: Route FOUND_ROWS to last used target This will cause the query to be routed to the same server where a possible SQL_CALC_FOUND_ROWS was executed. --- Documentation/Routers/ReadWriteSplit.md | 13 +++++++++++++ server/core/queryclassifier.cc | 15 +++++++++++++++ 2 files changed, 28 insertions(+) diff --git a/Documentation/Routers/ReadWriteSplit.md b/Documentation/Routers/ReadWriteSplit.md index fa6c76b3f..dea6e575b 100644 --- a/Documentation/Routers/ReadWriteSplit.md +++ b/Documentation/Routers/ReadWriteSplit.md @@ -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. diff --git a/server/core/queryclassifier.cc b/server/core/queryclassifier.cc index 38b83d5ce..879ea5894 100644 --- a/server/core/queryclassifier.cc +++ b/server/core/queryclassifier.cc @@ -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)) {