pingcap/tidb

Enable more expressions to be pushdown to TiKV

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#26,954 opened on Aug 6, 2021

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component/jsonhelp wantedsig/executiontype/enhancement

Description

Enhancement

There are some expressions that has been implemented in TiKV copr but the push down is not enabled. There are two reasons:

  1. The test is insufficient.
  2. The implementation is not compatible with MySQL because the underlying library is different(such as the math library).

For the first situation, we can add more testcase to ensure its correctness. Especially when Projection push down is finished, We can do testing with greater efficiency.

Misc

  • AnyValue
  • InetNtoa
  • InetAton
  • Inet6Ntoa
  • Inet6Aton
  • IsIPv4
  • IsIPv4Compat
  • IsIPv4Mapped
  • IsIPv6
  • BitAnd
  • BitOr
  • BitCount
  • Bin
  • UnHex
  • Sha2
  • Compress
  • Uncompress
  • RandomBytes
  • Password
  • FromBase64

Json

  • JsonDepth
  • JsonReplace
  • JsonKeys
  • JsonQuote

Math

  • abs
  • Pi
  • Sin
  • Asin
  • Cos
  • Acos
  • Tan
  • Atan
  • Atan2
  • Cot

String

  • locate
  • truncate
  • Regexp
  • ord
  • lpad
  • rpad
  • left
  • right
  • insert
  • upper
  • lower
  • makeset
  • substringIndex
  • instr
  • quote
  • octant
  • findInSet
  • CharLength
  • ToBase64
  • repeat

Time

  • WeekOfYear
  • DayOfWeek
  • Week
  • WeekDay
  • ToDays
  • ToSeconds
  • DateDiff
  • NullTimeDiff
  • AddDate
  • MakeDate
  • Hour
  • Minute
  • Second
  • MicroSecond
  • DayName
  • TimestampDiff
  • DateAdd
  • FromUnixTime

Contributor guide

Tech stack
gosql
Domain
backenddatabaseperformance
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Go programmingTiDB/TiKV architectureSQL expression semantics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
25
Research direction
Investigate the existing pushdown mechanism in TiDB's coprocessor module, specifically in the planner or executor. For each expression listed in the issue, determine if the TiKV side implementation exists and why pushdown is not enabled. Check test coverage and MySQL compatibility. Start with simpler expressions like 'abs' or 'sin' to understand the process and then proceed to more complex ones.