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https://issues.apache.org/jira/browse/CALCITE-5273?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17601465#comment-17601465
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Julian Hyde commented on CALCITE-5273:
--------------------------------------
What should RelToSqlConverter do? There's a good case that it should do what it
does now. Validating RelNode trees is not one of its responsibilities. Can you
make the case for and against?
If this tree can be produced from SQL (via parser, validator, sql-to-rel) then
things would be different.
> RelToSqlConverter allows unparsing of invalid CASE expression
> -------------------------------------------------------------
>
> Key: CALCITE-5273
> URL: https://issues.apache.org/jira/browse/CALCITE-5273
> Project: Calcite
> Issue Type: Bug
> Reporter: Ian Bertolacci
> Priority: Minor
>
> RelToSqlConverter will unparse the invalid† CASE expression {{`CASE ELSE 1
> END`}} (which can be constructed using either RelBuilder or RexBuilder, see
> CALCITE-5272).
> († Or at least and expression which Calcite then cannot parse.)
> Given this RelNode tree with invalid case statements
> {code}
> 1:LogicalProject($f0=[CASE(1)], $f1=[CASE(1:BIGINT)])
> 0:LogicalValues(tuples=[[{ 0 }]])
> {code}
> Unparsing with RelToSqlConverter using MysqlSqlDialect.DEFAULT‡ gives the Sql:
> {code}
> SELECT CASE ELSE 1 END AS `$f0`, CASE ELSE 1 END AS `$f1`
> {code}
> Running that sql back through the parser using Lex.MYSQL‡ and
> SqlConformanceEnum.MYSQL_5‡ throws the exception:
> {code}
> Incorrect syntax near the keyword 'CASE' at line 1, column 8.
> Was expecting one of:
> "ALL" ...
> "CURSOR" ...
> "DISTINCT" ...
> ...
> org.apache.calcite.sql.parser.SqlParseException: Incorrect syntax near
> the keyword 'CASE' at line 1, column 8.
> Was expecting one of:
> "ALL" ...
> "CURSOR" ...
> "DISTINCT" ...
> ...
> at
> org.apache.calcite.sql.parser.impl.SqlParserImpl.convertException(SqlParserImpl.java:389)
> at
> org.apache.calcite.sql.parser.impl.SqlParserImpl.normalizeException(SqlParserImpl.java:153)
> at
> org.apache.calcite.sql.parser.SqlParser.handleException(SqlParser.java:145)
> at
> org.apache.calcite.sql.parser.SqlParser.parseQuery(SqlParser.java:160)
> at org.apache.calcite.sql.parser.SqlParser.parseStmt(SqlParser.java:185)
> at org.apache.calcite.prepare.PlannerImpl.parse(PlannerImpl.java:214)
> at org.apache.calcite.tools.Planner.parse(Planner.java:50)
> ..
> Caused by: org.apache.calcite.sql.parser.impl.ParseException: Incorrect
> syntax near the keyword 'CASE' at line 1, column 8.
> Was expecting one of:
> "ALL" ...
> "CURSOR" ...
> "DISTINCT" ...
> ...
> at
> org.apache.calcite.sql.parser.impl.SqlParserImpl.convertException(SqlParserImpl.java:349)
> ... 59 more
> {code}
> ‡ I don't believe the specific dialect/lex/conformance parameters affect the
> outcome.
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