2018-07-02-tidb-weekly.md

title	date	summary	tags
Weekly update (June 25 ~ July 01, 2018)	2018-07-02	Last week, we landed 39 PRs in the TiDB repositories and 25 PRs in the TiKV and PD repositories.	TiDB TiKV PD

Weekly update in TiDB

Last week, we landed 39 PRs in the TiDB repositories.

Added

• Add a session variable tidb_ddl_reorg_worker_cnt to control the number of the DDL organization workers
• Support parallel HASH aggregation and greatly improve the performance of the aggregation function
• Print explain results in a tree style
• Support the SHOW ERRORS statement and improve the SHOW WARNINGS statement

Fixed

• Make the INSERT IGNORE statement ignore BadNullError
• Fix a bug when only_full_group_by is set in SQL_MODE
• Fix the wrong results of avg(double)
• Make the CREATE TABLE IF NOT EXISTS LIKE statement work again
• Set the correct startHandle when some errors occur in adding indexes
• Fix a bug in pushing down TopN
• Fix the response result bug of COM_FIELD_LIST
• Fix a bug of the str_to_date() function
• Fix a bug of the INSERT statement when the field type is unsigned float/double

Improved

• Use the average error of the row count which is estimated by statistics to determine the pseudo column
• Use CorrelatedColumn to calculate range
• Make the frequency of updating the statistic metadata depend on the table size
• Refactor the execution framework of the aggregate functions
• Speed up the CreateTable operation
• Stop calling expression.Clone in the plan package except ResolveIndices
• Handle \N as NULL in LOAD DATA
• Avoid holding the Write lock for a long time
• Reduce the memory usage in the INSERT INTO SELECT statement
• Enhance the row count estimation when the correlated column exists
• Check the character set capitalization when creating a table
• Improve the accessPath for the unique key

Weekly update in TiKV and PD

Last week, we landed 25 PRs in the TiKV and PD repositories.

Added

• Support splitting a Region by key using tikv-ctl
• Provide PerfContext statistics in Coprocessor
• Fuzz decimals
• Collect thread state metrics

Fixed

• Fix the issue that the store runs out of space due to moving replicas
• Fix a bug in do_sub when the last nonzero digit is before the point
• Fix potential stale Read during merging
• Handle heartbeats of Regions with changed peers

Improved

• Return the UnknownSignature error for unimplemented signatures
• Remove Box<> around Cursor, Snapshot and Engine
• Upgrade Rust to the nightly-2018-06-14 version

New contributors (Thanks!)

TiDB:

• cityonsky
• mail2fish

Docs:

• yejiayu