FrankChen021 commented on issue #18010:
URL: https://github.com/apache/druid/issues/18010#issuecomment-6473402231
> The test also shows that SUM('abc') and AVG('abc') return null instead of
failing.
I checked the impl to see how SUM/AVG plans the literal `abc` into
`null:DECIMAL(38, 19)` while MAX/MIN/quantile aggregator does not.
SUM/AVG declares the operand type as NUMERIC(see `DRUID_SUM` in
`SumSqlAggregator`) , MIN/MAX declares the operand type as `COMPARABLE_ORDERED`
and quantile declares the operand type to be `ANY`. This allows the quantile
functions accept any type, not only string, but also array because
`DefaultOperandTypeChecker` does nothing for `ANY` type.
So fixing the string literal only fixes part of the problem. To fix this
completely, we may need to:
1. update the `QuantileSqlAggregator` to define the 1st operand type to be
numeric or any
2. update `DefaultOperandTypeChecker` so that it checks:
2.1. if the operand is ComplexSqlType, check against if it's defined in
the operand allowed complex type
2.2. If the operand is a character literal that won’t parse, reject it
with the friendly InvalidSqlInput.
2.3. if the operand is coerciable, try coercion
This is a little complicated than a simple change in
`toDruidExpressionForNumericAggregator`.
For `null:DECIMAL(38, 19)` problem of SUM/AVG, we may need to update
`DruidTypeCoercion#builtinFunctionCoercion ` to check if the literal is
parsable. This can be done in a separate PR.
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