@Muhammad Gelban , since the SqlStdOperatorTable.CAST is hard coded , I think it's difficult to replace it absolutely with a new cast function now.
Lai Zhou <hhlai1...@gmail.com> 于2019年6月10日周一 下午6:54写道： > @Muhammad Gelban, I suggest you to find the the usages of an Operator > first , if you want to define a new one to replace it . > In this case, you will find that the SqlStdOperatorTable.CAST is used by > the Sql Converter, there're a few more places need attention. > You can refer to the solution of my custom sql engine , that shows how to > make a HiveSqlCastFunction to replace the default one. > > https://github.com/51nb/marble/blob/master/marble-table-hive/src/main/java/org/apache/calcite/adapter/hive/HiveSqlCastFunction.java > > https://github.com/51nb/marble/blob/83f0ea2941affbaf792a6290963ffc0b5277512f/marble-table-hive/src/main/java/org/apache/calcite/adapter/hive/HiveConvertletTable.java#L44 > > > > > > Muhammad Gelbana <m.gelb...@gmail.com> 于2019年6月9日周日 上午5:11写道： > >> I created a PR [1] to support the PostgreSQL :: casting operator. The way >> I >> did this is by creating a new 'SqlBinaryOperator' child. This new child >> wraps an instance of the 'SqlCastFunction' to reuse it's >> 'getOperandCountRange', >> 'inferReturnType', 'checkOperandTypes' and 'getMonotonicity' logic, and of >> course unparses to the original input (i.e. op1 :: type). >> >> But then the PR was commented to reuse the 'SqlCastFunction' type instead >> of having a totally new 'SqlBinaryOperator', wich won't unparse properly >> because 'op1 :: type' will be unparsed as 'CAST(op1 AS type)'. >> >> Is this a big deal ? I prefer to preserve the orignal format for the >> parsed >> string but to do that I'll have to extend 'SqlCastFunction' to override >> it's 'unparse' implementation (I don't remember why I didn't do that, the >> PR is like 3 months old) >> >> So is preserving the original structure necessary, recommended or a must >> while unparsing ? >> If there are any related restriction I need to follow while working on >> this, please let me know. >> >> [1] https://github.com/apache/calcite/pull/1066 >> >> Thanks, >> Gelbana >> >
