Feng Zhu created CALCITE-3414: --------------------------------- Summary: Unify Expression'type cast and conversion as a robust one Key: CALCITE-3414 URL: https://issues.apache.org/jira/browse/CALCITE-3414 Project: Calcite Issue Type: Bug Components: core Affects Versions: 1.21.0 Reporter: Feng Zhu Assignee: Feng Zhu Attachments: RexToLixTranslator.png, TypeConversion.txt, Types.png
Current now, there are two functions in calcite that can be used to cast/convert Expression to a specific Type. *_Types.castIfNecessary_* and _*RexToLixTranslator.convert*_. We make a deep investigation on their implementations and demonstrate them as below. {color:#ff0000} !RexToLixTranslator.png!{color} {color:#ff0000} *RexToLixTranslator.convert*{color} !Types.png! {color:#ff0000} *Types.castIfNecessary*{color} It can be seen that: (1) They have a lot of overlaps; (2) *_RexToLixTranslator.cast_* can cover more cases with tools like _SqlFunctions_ and etc. (3) Both of them have limitations and may generate incorrect code, which is listed in attachment(TypeConversion.txt). Multiple choices usually bring confusion to developers and resulting to the misuse of them. For example, CALCITE-3245 exposes that Types.castIfNecessary cannot cast the Expression to BigDecimal.class. Fixing the issue in *_Types.castIfNecessary_* directly seems to be not a good idea. On one hand, it is not convenient to call _SqlFunctions_ in linq4j. One the other hand, it will brings duplicate with _*RexToLixTranslator.cast*_. However, due to some unique logic in _*Types.castIfNecessary*_, we cannot replace it as _*RexToLixTranslator.cast*_ neither. Therefore, it is a good idea to integrate implementations into RexToLixTranslator.cast. -- This message was sent by Atlassian Jira (v8.3.4#803005)