Weekly update in TiDB

Last week, we landed 51 PRs in the TiDB repositories.

Added

• Support setting variables with ON and OFF.
• Support show stats_histgrams and show stats_buckets for debugging.
• Support the Scan API for the raw KV interface.
• Support the Show Charset statement.
• Support user name without quotes such as `root@127.0.0.1`.

Fixed

• Fix a bug when explicitly inserting the null value into columns with the timestamp type.
• Do not check privileges for the information_schema database.
• Correct the error message for the authentication error.
• Fix a bug in the cast function with an unsigned type.

Improved

• Refactor optimizer:
  • Select Join operator by CBO framework automatically: #3623, #3737, #3761
  • Use statsProfile to estimate count and cardinality.
• Refactor the builtin function evaluation framework:
  • left & right
  • lower & upper
  • concat_ws
  • to_base64
  • md5
  • space
  • replace
  • substring/substr
  • compare
  • uuid
  • bit_length
  • log10
  • Move the type inference work from typeinfer to expression rewritter: aggregate expression, column & constant expression
• Close the connection after sending ERR_Packet.
• Improve the unit test coverage for parser packages.

Weekly update in TiKV

Last week, We landed 23 PRs in the TiKV repositories.

Added

• Add json_modify, math function evaluators for the coprocessor.
• Pass the compression type to generate snapshot SST.
• Set 256 MB as the default region size.
• Add the raw Scan API.

Fixed

• Ignore the command that removes the leader itself.
• Fix diff hint overflow.
• Rotate PD log by default.
• Fix the leap second problem in Go 1.9.
• Clean up stale metadata when start.

Improved

• Reduce the lock scope for region heartbeat.
• Send the raft messages in batch.
• Refactor the coprocessor code directory.
• Enable the pipelined write.
• Remove unnecessary hash group keys.