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Yuzhao Chen commented on CALCITE-2302: -------------------------------------- hi, [~julianhyde] I have made a PR here [CALCITE-2302|https://github.com/apache/calcite/pull/706], really appreciate that you can give me some suggestions. > Implicit type cast support > -------------------------- > > Key: CALCITE-2302 > URL: https://issues.apache.org/jira/browse/CALCITE-2302 > Project: Calcite > Issue Type: Improvement > Components: core > Affects Versions: 1.17.0 > Reporter: Yuzhao Chen > Assignee: Julian Hyde > Priority: Major > Fix For: 1.17.0 > > > 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: > # Now we use a validator to validate our operands types[ through kinds of > namespaces and scopes ] > # Most of the validations will finally goes to > {code:java} > SqlOperator.validateOperands > {code} > # 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: > # Supply a tool class/rules to add casts into a parsed SqlNode tree which > will then go through the validation logic later on. > # 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 [https://github.com/apache/calcite/pull/706,] > This is design doc: [Calcite Implicit Type Cast > Design|https://docs.google.com/document/d/1g2RUnLXyp_LjUlO-wbblKuP5hqEu3a_2Mt2k4dh6RwU/edit?usp=sharing]. > This is the conversion types mapping: [Conversion Types > Mapping|https://docs.google.com/spreadsheets/d/1GhleX5h5W8-kJKh7NMJ4vtoE78pwfaZRJl88ULX_MgU/edit?usp=sharing]. > I really appreciate your suggestions, thx. -- This message was sent by Atlassian JIRA (v7.6.3#76005)