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https://issues.apache.org/jira/browse/CALCITE-6937?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17940842#comment-17940842
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Yu Xu commented on CALCITE-6937:
--------------------------------
[~julianhyde] Yes, REAL type should map directly to FLOAT in Hive, such as
Spark behavior in description, it would map to FLOAT type and is 32bit
floating point when cast to real and Spark other all data types consistent
with Hive，as I know other popular engines(mysql/oracle/snowflake/ClickHouse)
also make real equivalent to FLOAT type.
> Hive/Phoenix can not support REAL type
> --------------------------------------
>
> Key: CALCITE-6937
> URL: https://issues.apache.org/jira/browse/CALCITE-6937
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.39.0
> Reporter: Yu Xu
> Assignee: Yu Xu
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.40.0
>
>
> REAL type should equivalent to FLOAT type in Calcite（can refer to
> [https://calcite.apache.org/docs/reference.html#scalar-types]），but some
> systems not support REAL type, such as Hive//Phoenix, so in Dialect covnert
> from REAL to REAL is not consistent with these data system.
>
> *floating-point data type only support FLOAT and DOUBLE in follow systems:*
>
> Phoenix: [https://phoenix.apache.org/language/datatypes.html]
>
> Hive: [https://cwiki.apache.org/confluence/display/Hive/LanguageManual+Types]
>
> *in Hive test which is not supported:*
> hive> select cast(1.2 as REAL);
> NoViableAltException(26@[])
> at
> org.apache.hadoop.hive.ql.parse.HiveParser.primitiveType(HiveParser.java:39374)
> at
> org.apache.hadoop.hive.ql.parse.HiveParser_IdentifiersParser.castExpression(HiveParser_IdentifiersParser.java:5434)
> at
> org.apache.hadoop.hive.ql.parse.HiveParser_IdentifiersParser.atomExpression(HiveParser_IdentifiersParser.java:6716)
> at
> org.apache.hadoop.hive.ql.parse.HiveParser_IdentifiersParser.precedenceFieldExpression(HiveParser_IdentifiersParser.java:6879)
> at
> org.apache.hadoop.hive.ql.parse.HiveParser_IdentifiersParser.precedenceUnaryPrefixExpression(HiveParser_IdentifiersParser.java:7264)
> at
> org.apache.hadoop.hive.ql.parse.HiveParser_IdentifiersParser.precedenceUnarySuffixExpression(HiveParser_IdentifiersParser.java:7324)
> at
> org.apache.hadoop.hive.ql.parse.HiveParser_IdentifiersParser.precedenceBitwiseXorExpression(HiveParser_IdentifiersParser.java:7508)
> at
> org.apache.hadoop.hive.ql.parse.HiveParser_IdentifiersParser.precedenceStarExpression(HiveParser_IdentifiersParser.java:7668)
> at
> org.apache.hadoop.hive.ql.parse.HiveParser_IdentifiersParser.precedencePlusExpression(HiveParser_IdentifiersParser.java:7828)
> at
> org.apache.hadoop.hive.ql.parse.HiveParser_IdentifiersParser.precedenceAmpersandExpression(HiveParser_IdentifiersParser.java:7988)
> at
> org.apache.hadoop.hive.ql.parse.HiveParser_IdentifiersParser.precedenceBitwiseOrExpression(HiveParser_IdentifiersParser.java:8147)
> at
> org.apache.hadoop.hive.ql.parse.HiveParser_IdentifiersParser.precedenceEqualExpression(HiveParser_IdentifiersParser.java:8677)
> FAILED: ParseException line 1:19 cannot recognize input near 'REAL' ')'
> '<EOF>' in primitive type specification
>
> *in Phoenix also not supported:*
> phoenix> select cast(1.2 as REAL);
> Error: ERROR 201 (22000): Illegal data. Unsupported sql type: REAL
> (state=22000,code=201)
> java.sql.SQLException: ERROR 201 (22000): Illegal data. Unsupported sql type:
> REAL
>
> *but in Spark it is work well(convert to float type):*
> spark-sql> select cast(1.1 as real);
> 25/04/02 22:36:56 WARN TaskSetManager: Finished tasks (1/1) in stage 2.0
> OK
> CAST(1.1 AS FLOAT)
> 1.1
> Time taken: 2.113 seconds, Fetched 1 row(s)
>
> *so in Hive/Phoenix system need convert from real to float type.*
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