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## What have you changed? (mandatory)
During coprocessor dag task, it first uses timezone `name`, if non-empty, to get legitimate timezone variable. To achieve this, we need to push down such data into tikv which leads to change the logic of building pushdown request. The logic I mentioned mainly resides in `executor` package.
I change `timeZoneOffset` to `zone` and add second return parameter `name string`. The intentioned of doing this to adopt the convention of `time` package.
For the same purpose, I change `GetTimeZone` to `Location`. As you can see, in `time` package, timezone was bind to `Location`.
## What are the type of the changes (mandatory)?
- Bug fix (non-breaking change which fixes an issue)
## How has this PR been tested (mandatory)?
unit-test
integration-test will be added shortly
* *: remove non-prepared plan cache
non-prepared plan cache is not usable if we can only do full string match.
And further development doesn't worth the effort.
`kill tidb connID`, if the user is the owner of that connection, there
is no need to check the SUPER privilege.
SessionManager interface is slightly modified.
'load data' is not retryable when it meets conflicts, while latches may result in
false positive transaction conflicts. so enable latches will lead to 'load data'
abort abnormally, even there are no conflicts.
when 'only_full_group_by' is set in sql_mode, raise error for non-aggregated column in query without GROUP BY.
mysql> create table t(a bigint, b bigint, c bigint); Query OK, 0 rows affected (0.02 sec)
mysql> select a, max(b) from t;
ERROR 1140 (42000): In aggregated query without GROUP BY, expression #1 of SELECT list contains nonaggregated column 'dc_test.t.a'; this is incompatible with sql_mode=only_full_group_by
