Calcite works best when it is able to execute the SQL that it accepts. If we
were to allow say DECIMAL(200, 5) we would need to be able to generate Java
code that can handle values of that type. The current maximum, DECIMAL(19), can
be handled by 64-bit signed integers (Java long).
> On Aug 7, 2023, at 7:18 PM, Ran Tao <chucheng...@gmail.com> wrote:
>
> hi, mbudiu.
>
> I get your point. Ofcourse, we can override `RelDataTypeSystemImpl`.
> however, my suggestion is that we change the maximum 19 of
> `RelDataTypeSystemImpl` to meet the mature engines,
> If there is no specific reason for setting the maximum value of 19.
>
> <mbu...@gmail.com> 于2023年8月8日周二 01:03写道：
>
>> Calcite gives you hooks to change these limits.
>>
>> For example:
>>
>> public static final RelDataTypeSystem TYPE_SYSTEM = new
>> RelDataTypeSystemImpl() {
>> @Override
>> public int getMaxNumericPrecision() {
>> return MAX_PRECISION;
>> }
>> @Override
>> public int getMaxNumericScale() {
>> return MAX_SCALE;
>> }
>> @Override
>> public boolean shouldConvertRaggedUnionTypesToVarying() { return
>> true; }
>> };
>>
>>
>> this.typeFactory = new SqlTypeFactoryImpl(TYPE_SYSTEM);
>>
>> Then you can use this type factory in other structures you build, like the
>> CatalogReader, the Validator, and the Cluster.
>>
>>
>> -----Original Message-----
>> From: Ran Tao
>> Sent: Sunday, August 06, 2023 7:58 PM
>> To: dev@calcite.apache.org
>> Subject: [DISCUSS] Increase the default maximum precision and scale of the
>> number type
>>
>> Hi, devs. I have noticed that currently calcite default maximum precision
>> and scale is 19.
>> If we set Decimal(50,2), it will reduce to Decimal(19,2).
>> while other mature database systems or bigdata engines have more bigger
>> value.
>>
>> For consistency and to give calcite users a standard value that meets most
>> engines, can we adjust the value of calcite to 38?
>>
>> Besides, the sql standard defines the meaning of precision and scale,
>> letting each system customize the maximum precision and scale. (sql1999,
>> page 125)
>>
>> engine precision range scale range
>> calcite [1,19] [1,19]
>> oracle [1,38] [-84,127]
>> sqlserver [1,38] [0,38]
>> mysql [1,65] [0,30]
>> spark [1,38] [0,38]
>> hive [1,38] [0,38]
>> flink [1,38] [0,38]
>> We can see many systems or engines follow the sql standard to make maximum
>> precision and scale to be 38, except oracle and mysql.
>>
>> If anyone can share some history or reasons why calcite set 19, i will
>> appreciate it.
>>
>> [1]
>>
>> https://docs.oracle.com/en/database/oracle/oracle-database/19/sqlqr/Data-Types.html#GUID-DCCC6F18-15A0-4ECC-BA48-16F73F844844
>>
>> [2]
>>
>> https://learn.microsoft.com/en-us/sql/t-sql/data-types/decimal-and-numeric-transact-sql?view=sql-server-ver15
>>
>> [3]
>>
>> https://dev.mysql.com/doc/refman/8.0/en/precision-math-decimal-characteristics.html
>>
>> [4]
>>
>> https://spark.apache.org/docs/3.2.0/api/java/org/apache/spark/sql/types/DecimalType.html
>>
>> [5]
>>
>> https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=82706456#LanguageManualTypes-decimal
>>
>> [6]
>>
>> https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/table/api/DataTypes.html
>>
>>
>> Best Regards,
>> Ran Tao
>> https://github.com/chucheng92
>>
>>
