fixed bugs

  1) Add column and import cause " TDengine Error: others"
  2) Data file corruption during multi-copy synchronization
  3)

enhancements
  1) Enhanced security permissions

add some log for parsing insertion SQL and showing complete insertion…

… SQL

enhancements

  1) In the query of super tables, all subquery objects are prepared before lauching and some checks for global status check are added;
  2) Failed login information would be store in the 'log' database and the access to this database has be limited;

fixed bugs

  1) query results could be incorrect when sorting the results by descending timestamp and using offset/limit
  2) query of last record could lead to server crash
  3) the display could be incorrect when show vnodes [dnodeIp]
  4) Group by normal column may result in server crash

enhancements
  1) add support for customized template variable for query alias in the grafana
  2) add support for Alpine Linux
  3) avoid repetitively parsing the same table when inserting records into multiple tables in a batch
  4) accelerate the speed of writing into a database with multiple replicas by redirecting the request to the master vnode
  5) allow dropping database and inserting data to be concurrently executed

fixed bugs

  1) in the windows query results from grouping by a nchar column could be inconsistent with that from taos cliEnt shell in the linux
  2) query of last record could lead to server crash
  3) both inserting data and creating dropped tables would fail if setting 'tables' option to 1

enhancements
  ) avoid repetitively parsing the same table when inserting records into multiple tables in a batch
  2) accelerate the speed of writing into a database with multiple replicas by redirecting the request to the master vnode
  3) clarify the error message when importing multiple files

Merge pull request taosdata#979 from taosdata/feature/grafana_plugin

Feature/grafana plugin

1.taosdata#952 Logical error when setting read and write permissions …

…for the user

2.taosdata#949 SQL statement `show connections` may cause crash
3.taosdata#946 Filter on all NULL value cause the server crashed
4.taosdata#928 Use multi-threading to import all SQL files in the directory separately
5.Asynchronous query loop too many times when pulling cache

1.Better support for publicIP

2.Use object reference to manage the life cycle for the QInfo object
3.The server crashed when tag group by
4.Some problems in join statement
5.Remove warning from compiler

1.Vnode may fail to recycle when deleting database

2.The error code returned by the aggregation calculation is incorrect

1.Dealing with duplicate vgroup numbers