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https://issues.apache.org/jira/browse/DRILL-2064?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14395410#comment-14395410
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Daniel Barclay (Drill) commented on DRILL-2064:
-----------------------------------------------
In considering the renaming, note that SQL's lower- and higher-precision types
are REAL and DOUBLE PRECISION, not FLOAT and DOUBLE PRECISION:
The SQL spec (ISO/IEC 9075:2011 Part 2 ยง 6.1 <data type>) says:
- <approximate numeric type> ::=
FLOAT [ <left paren> <precision> <right paren> ]
| REAL
| DOUBLE PRECISION
...
- If a <precision> is omitted, then an implementation-defined <precision> is
implicit.
...
- REAL specifies the data type approximate numeric, with implementation-defined
precision.
- DOUBLE PRECISION specifies the data type approximate numeric, with
implementation-defined precision
that is greater than the implementation-defined precision of REAL.
- FLOAT specifies the data type approximate numeric, with binary precision
equal to or greater than the
value of the specified <precision>. The maximum value of <precision> is
implementation-defined. <precision>
shall not be greater than this value.
That is:
- SQL REAL must map in Drill to Java float and the things currently named with
"Float4" (so that DOUBLE PRECISION can have greater precision than it).
- SQL DOUBLE PRECISION maps to Java double and the things currently named with
"Float8" (so that is has greater precision that REAL does).
- SQL FLOAT can map to whichever (of float/Float4 and double/Float8) Drill
chooses (and Drill is supposed to document the chosen precision).
- SQL FLOAT(<precision>) must map to Java double/etc. if <precision> is greater
than 24. (If the requested precision is less, FLOAT(<precision>) can be mapped
to either of float/Float4 or double/Float8.)
> Internal "Float4" and "Float8" names are confusing; rename using "Float" and
> "Double"
> -------------------------------------------------------------------------------------
>
> Key: DRILL-2064
> URL: https://issues.apache.org/jira/browse/DRILL-2064
> Project: Apache Drill
> Issue Type: Bug
> Components: Execution - Data Types
> Reporter: Daniel Barclay (Drill)
> Priority: Minor
> Fix For: 1.0.0
>
>
> [For/from Jacques:]
> The internal names (e.g., enumerations, vector subtypes, function names)
> containing "Float4" and "Float8" are confusing since they don't correspond to
> type names "float" and "double" in Java, etc.
> Things currently named using "Float4" should be renamed to names using
> "Float"; things currently named using "Float8" should be renamed using
> "Double".
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