rubenada commented on a change in pull request #2555:
URL: https://github.com/apache/calcite/pull/2555#discussion_r718702589
##########
File path:
core/src/main/java/org/apache/calcite/sql/type/SqlTypeCoercionRule.java
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@@ -202,7 +202,8 @@ private SqlTypeCoercionRule(Map<SqlTypeName,
ImmutableSet<SqlTypeName>> map) {
coerceRules.copyValues(SqlTypeName.BOOLEAN)
.add(SqlTypeName.CHAR)
.add(SqlTypeName.VARCHAR)
- .addAll(SqlTypeName.NUMERIC_TYPES)
+ .addAll(SqlTypeName.INT_TYPES)
+ .addAll(SqlTypeName.APPROX_TYPES)
Review comment:
`SqlTypeName.APPROX_TYPES` include `FLOAT`, `REAL` and `DOUBLE`. Are we
sure casting these types into boolean always work?
It's strange, it seems that `SELECT CAST(CAST(0 AS float) AS BOOLEAN)` works
fine (returns `false`). But if we try a more "complex" query: `select
cast(cast(p0 as float) as boolean) from (values (0)) as t(p0)` ; it will fail
at runtime with `CompileException: Line 21, Column 31: Cannot cast "double" to
"boolean"`.
This type of query will be generated if we add these tests into
`SqlOperatorBaseTest#testCastToBoolean`:
```
tester.checkBoolean("cast(cast(0 as float) as boolean)", Boolean.FALSE);
tester.checkBoolean("cast(cast(0 as real) as boolean)", Boolean.FALSE);
tester.checkBoolean("cast(cast(0 as double) as boolean)", Boolean.FALSE);
```
which, if I am not mistaken, will fail if we add them to
`SqlOperatorBaseTest#testCastToBoolean`. Therefore, perhaps we should consider
`FLOAT`, `REAL` and `DOUBLE` (together with `DECIMAL`) as non-castable into
boolean?
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