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  1. Calcite
  2. CALCITE-2302

Implicit type cast support

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Details

    • Improvement
    • Status: Closed
    • Critical
    • Resolution: Fixed
    • 1.17.0
    • 1.21.0
    • core

    Description

      Now many DBs have support implicit type cast, eg: SqlServer, Oracle, Hive.

      Implicit type cast is an useful function for many cases, So we should support this.

      I checkout Calcite code and found that:

      1. Now we use a validator to validate our operands types[ through kinds of namespaces and scopes ]
      2. Most of the validations will finally goes to
        SqlOperator.validateOperands
        
      1. which will use validation logic defined in corresponding SqlOperandTypeChecker

      What i'm confused about is where should i put the implicit type cast logic in? I figured out 2 ways:

      1. Supply a tool class/rules to add casts into a parsed SqlNode tree which will then go through the validation logic later on.
      2. Unleash the validation logic in kinds of SqlOperandTypeChecker, then modify the RelNode/RexNodes tree converted from a validated SqlNode tree to add in casts through custom RelOptRules.

      So guys, which of the 2 ways should i go, or if there are better way to do this?

      I need your help.

       

      Updated 18-05-30:

      Hi guys, i have made a PR in CALCITE-2302

      This is design doc: Calcite Implicit Type Cast Design.

      This is the type conversion matrix: Type Conversion Matrix.

      I really appreciate your suggestions, thx.

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              danny0405 Danny Chen
              danny0405 Danny Chen
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