| Bug #76007 | get_default_num_partitions() called when number of partitions are known | ||
|---|---|---|---|
| Submitted: | 23 Feb 2015 14:49 | Modified: | 11 Mar 2015 16:05 |
| Reporter: | Magnus Blåudd | Email Updates: | |
| Status: | Closed | Impact on me: | |
| Category: | MySQL Server: Partitions | Severity: | S2 (Serious) |
| Version: | 5.7.6 | OS: | Any |
| Assigned to: | CPU Architecture: | Any | |
[11 Mar 2015 16:05]
Jon Stephens
Documented as follows in the 5.7.7 changelog:
The MySQL Server unnecessarily requested the default number of
partitions for a table whenever it opened a partitioned table.
This was unnecessary since the server already has this
information about the table to be opened. Now the server
requests this information only when needed--that is, only
if it is creating or altering a partitioned table.
Closed.
Description: MySQL Server unnecessarily asks for the default number of partitions for a table when opening a partitioned table. This is not necessary since the MySQL Server already knows how many partitions the table it want to open has. Only when the table is to be created or altered is there a need to know the default value. open() part_info.num_parts = Partition_handler::get_num_parts("t1"); default_partitions = Partition_handler::get_default_num_partitions(); How to repeat: This was detected when merging down 5.7.6 into trunk-cluster, queries ran just after mysqld connected to the cluster failed more often. Code inspection showed that ha_ndbcluster::get_default_num_partitions() was being called before opening the table. Suggested fix: Don't call Partition_handler::get_default_num_partitions() when opening a table. The function should only be used when creating a new table and the user has not specified number of partitions. I'm quite sure the function is currently also used when altering a table, that use case seems wrong since the number of partitions in the target table should be the same as source table. Anyway, this bug is about making it not called as part of or before opening a table. Theoretically the get_default_num_partitions() should be a handlerton function or at least a Partition_handler class function(i.e static).