[jira] [Commented] (CALCITE-5104) Select with CURRENT_DATE without alias produces alias that can't be parsed by Calcite itself

["yanjing.wang (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-5104?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17524962#comment-17524962 ] 

yanjing.wang commented on CALCITE-5104:
---------------------------------------

Hi [~FDoKE] , the current_date is a sql call derived from a sql identifier, I think its alias should be generated rather than derived from an identifier. It may be better use 'newAlias' rather 'alias' when SqlStdOperatorTable.AS.createCall, how do you think?

> Select with CURRENT_DATE without alias produces alias that can't be parsed by Calcite itself
> --------------------------------------------------------------------------------------------
>
>                 Key: CALCITE-5104
>                 URL: https://issues.apache.org/jira/browse/CALCITE-5104
>             Project: Calcite
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 1.30.0
>            Reporter: Vyacheslav Puzakov
>            Priority: Major
>
> Validator configured with 
> {code:java}
> validatorConfig.withIdentifierExpansion(true){code}
> In case of this original query:
> {code:java}
> select current_date from emp{code}
> validator produces next sql node:
> {code:java}
> SELECT CURRENT_DATE AS CURRENT_DATE
> FROM "CATALOG"."SALES"."EMP" AS "EMP"{code}
>  
> Where CURRENT_DATE used as simple *Alias*
> If you try to parse that syntax, Calcite will fail with:
> {code:java}
> Caused by: org.apache.calcite.sql.parser.SqlParseException: Incorrect syntax near the keyword 'CURRENT_DATE' at line 1, column 24.
> Was expecting one of:
>     <QUOTED_STRING> ...
>     <BRACKET_QUOTED_IDENTIFIER> ...
>     <QUOTED_IDENTIFIER> ...
>     <BACK_QUOTED_IDENTIFIER> ...
>     <BIG_QUERY_BACK_QUOTED_IDENTIFIER> ...
>     <HYPHENATED_IDENTIFIER> ...
>     <IDENTIFIER> ...
>     <UNICODE_QUOTED_IDENTIFIER> ...{code}
>  
> *I tracked down a problem causing it:*
> SqlValidatorImpl.java
> Line 435:
> {code:java}
> final String alias =
>     deriveAliasNonNull(
>         selectItem,
>         aliases.size()); {code}
> produces "current_date" as alias
> And then on the line 448 it applies:
> {code:java}
> expanded =
>     SqlStdOperatorTable.AS.createCall(
>         selectItem.getParserPosition(),
>         expanded,
>         new SqlIdentifier(alias, SqlParserPos.ZERO)); {code}
> When this identifier *unparses* (SqlUtil.java)
> {code:java}
> public static void unparseSqlIdentifierSyntax(
> ...
> final SqlOperator operator = isUnquotedSimple
>     ? SqlValidatorUtil.lookupSqlFunctionByID(SqlStdOperatorTable.instance(), identifier, null)
>     : null;{code}
>  
> It finds that this identifier has *operator* as its *isUnquotedSimple* and putting it without quotes.
>  
> *Possible solutions:*
> 1) Change to SqlParserPos.QUOTED_ZERO which will produce valid syntax after unparsing, but will affect a lot results
> in this case result will be (which parsed succesfully):
> {code:java}
> SELECT CURRENT_DATE AS "CURRENT_DATE"
> FROM "CATALOG"."SALES"."EMP" AS "EMP"{code}
> 2) A bit smarter move - check that this identifier is reserved keyword  (function which parser can't handle in AS operator) and force quotes only in this case.
>  
>  



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