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https://issues.apache.org/jira/browse/CALCITE-6991?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17948255#comment-17948255
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Mihai Budiu commented on CALCITE-6991:
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Indeed, CASE uses type coercion, while COALESCE does not.
So one of them must be wrong, or the translation from COALESCE to CASE is
incorrect.
> Validator cannot infer type for COALESCE when call is not expanded
> ------------------------------------------------------------------
>
> Key: CALCITE-6991
> URL: https://issues.apache.org/jira/browse/CALCITE-6991
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.39.0
> Reporter: Mihai Budiu
> Priority: Minor
>
> By default the validator rewrites calls such as COALESCE into CASE.
> This is controlled by the callRewrite() flag of SqlValidator.Config.
> When this flag is turned off, the validator will throw on an expression such
> as the following:
> {code:sql}
> SELECT COALESCE(DATE '2020-01-01', '2020-01-01')
> {code}
> This is the stack trace:
> {code}
> java.lang.IllegalArgumentException: Cannot infer return type for COALESCE;
> operand types: [DATE, CHAR(10)]
> at
> org.apache.calcite.sql.SqlOperator.inferReturnType(SqlOperator.java:566)
> at
> org.apache.calcite.sql.SqlOperator.validateOperands(SqlOperator.java:531)
> at org.apache.calcite.sql.SqlFunction.deriveType(SqlFunction.java:350)
> at org.apache.calcite.sql.SqlFunction.deriveType(SqlFunction.java:232)
> at
> org.apache.calcite.sql.validate.SqlValidatorImpl$DeriveTypeVisitor.visit(SqlValidatorImpl.java:7100)
> at
> org.apache.calcite.sql.validate.SqlValidatorImpl$DeriveTypeVisitor.visit(SqlValidatorImpl.java:7087)
> at org.apache.calcite.sql.SqlCall.accept(SqlCall.java:168)
> at
> org.apache.calcite.sql.validate.SqlValidatorImpl.deriveTypeImpl(SqlValidatorImpl.java:2034)
> at
> org.apache.calcite.sql.validate.SqlValidatorImpl.deriveType(SqlValidatorImpl.java:2021)
> {code}
> COALESCE should insert the same implicit casts that the expansion does if the
> two expressions are truly equivalent.
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