Yuzhao Chen created CALCITE-2302:
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Summary: Implicit type cast support
Key: CALCITE-2302
URL: https://issues.apache.org/jira/browse/CALCITE-2302
Project: Calcite
Issue Type: Improvement
Components: core
Affects Versions: 1.17.0
Reporter: Yuzhao Chen
Assignee: Julian Hyde
Fix For: 1.17.0
Now many BDs have support implicit type cast, eg: SqlServer, Oracle, Hive.
Implicit type cast is an useful function for many cases, So we should support
this.
I checkout Calcite code and found that:
# Now we use a validator to validate our operands types[ through kinds of
namespaces and scopes ]
# Most of the validations will finally goes to
{code:java}
SqlOperator.validateOperands
{code}
# which will use validation logic defined in corresponding SqlOperandTypeChecker
What i'm confused about is where should i put the implicit type cast logic in ?
There are several ways i figured out:
# Supply a tool class/rules to add casts into a parsed SqlNode tree which will
then go through the validation logic later on.
# Unleash the validation logic in kinds of SqlOperandTypeChecker, then modify
the RelNode/RexNodes tree converted from a validated SqlNode tree to add in
casts.
So guys, i need your help, which of the 2 ways should i go, or if there are
better way to do this?
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