Invalidating query cache entries replication

08-May-2019 11:22 by 5 Comments

Invalidating query cache entries replication - dating antique wall clocks

Query Cache::invalidate_table locks the query cache, invalidates the QC if query_cache_size 0, unlocks QC and returns.The current code actually locks/unlocks the query_cache lock twice when the query_cache_size is zero! This can all be bypassed if the check for query_cache_size is done without holding the QC lock as in Query_cache::store_query The CPU time wasted is very less, however, in benchmark situations, every cpu cycle counts.

This makes it difficult to make a good decision without showing the concrete performance consequences to each decision.

You can access the patch from: 2917 Kristofer Pettersson 2008-11-07 Bug#38551 query cache can still consume [very little] cpu time even when it is off.

By using the command line option --query_cache_type=0, the user can disable the query cache permanently and avoid taking the query cache mutex.

You can access the patch from: 2742 Kristofer Pettersson 2008-10-27 Bug#38551 query cache can still consume [very little] cpu time even when it is off.

By using the command line option --query_cache_type=0, the user can disable the query cache permanently and avoid taking the query cache mutex. After review, it may be pushed to the relevant source trees for release in the next version. After review, it may be pushed to the relevant source trees for release in the next version.

You can access the patch from: 2743 Kristofer Pettersson 2008-10-27 Bug#38551 query cache can still consume [very little] cpu time even when it is off. You can access the patch from: 2742 Kristofer Pettersson 2008-10-28 Bug#38551 query cache can still consume [very little] cpu time even when it is off.

You can access the patch from: 2742 Kristofer Pettersson 2008-10-29 Bug#38551 query cache can still consume [very little] cpu time even when it is off.

(2 servers version 5.1, and 2 version 5.5) While checking the slave status, i see the seconds_behind_master at 0, and half a second after i see it jumps to 2000, and so fourth. Easiest demonstrated with a slightly simpler replication topology: server1 - server3 If server2 falls behind, and is processing some long-running queries, the following will happen, assuming as start point: : Everyone ok : server1 writes two 10-minute queries to the binlog, no replication delay anywhere : server2 starts processing query one. : server2 is done with query 2, replication delay zero again.

Replication delay for server2 starts growing, replication delay for server3 stays zero : server2 is done with query one, starts processing query two. Server3 will be done with query 3, replication delay jumps back to zero, and then back up to 10 as it processes the next query.

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. When creating a test table in server 4, checking the relay log in server 1 shows the create statement was copied to the relay log in server 1 instantly, but the table is not created. Servers 1 2 & 4 were having "invalidating query cache entries (table)" stuck in their replication thread.

Visit Stack Exchange I'm running a 4 servers master-master cluster of My Sql. Replication topology: 1 - 1 UPDATE It seems that server 3 has its SBM at 0, while the other servers are jumping up and down. It looks like the server is busy doing something, and there is a huge delay between when the server gets the statement, and when it executes it. After disabling cache, server 4 is ok but 1&2 are still having this issue. id=60696 If anyone knows how to fix it, i would be glad to hear There is one flaw with mysql's seconds_behind_master value: it only takes into account the position relative to one upstream hop away.

on the old non-Percona servers which caused the replication to halt until the cache was invalidated (Which took a lot of time). id=60696 We solved the issue by moving entirely to Percona My SQL server v5.5 which has the ability to disable Query Cache completely.