zzwqqq created CALCITE-7529:
-------------------------------
Summary: RexExecutor constant reduction loses sub-millisecond
precision for TIME/TIMESTAMP literals
Key: CALCITE-7529
URL: https://issues.apache.org/jira/browse/CALCITE-7529
Project: Calcite
Issue Type: Bug
Components: core
Reporter: zzwqqq
When a custom RelDataTypeSystem allows datetime precision greater than
Calcite's default maximum precision, RexExecutor constant reduction can lose
sub-millisecond precision for TIME and TIMESTAMP values.
Calcite's default RelDataTypeSystem limits TIME/TIMESTAMP precision to 3, but
users can override RelDataTypeSystem#getMaxPrecision. With such a type system,
RexBuilder can be configured to create TIME(6) and TIMESTAMP(6) literals backed
by TimeString/TimestampString.
However, RexExecutorImpl reduces constant expressions through generated Java
code, where TIME and TIMESTAMP values are represented using millisecond-based
runtime values. When RexExecutable.reduce rebuilds a RexLiteral from those
values, digits beyond milliseconds are lost.
Minimal reproduction:
{code:java}
@Test void testReduceCastToTimeKeepsPrecision() {
final RelDataTypeFactory typeFactory =
new JavaTypeFactoryImpl(
new RelDataTypeSystemImpl() {
@Override public int getMaxPrecision(SqlTypeName typeName) {
switch (typeName) {
case TIME:
case TIMESTAMP:
return 6;
default:
return super.getMaxPrecision(typeName);
}
}
});
final RexBuilder rexBuilder = new RexBuilder(typeFactory);
final RexExecutorImpl executor =
new RexExecutorImpl(
DataContexts.of(
ImmutableMap.of(
DataContext.Variable.TIME_ZONE.camelName,
TimeZone.getTimeZone("GMT"),
DataContext.Variable.LOCALE.camelName, Locale.US)));
final RexNode cast =
rexBuilder.makeCast(
typeFactory.createSqlType(SqlTypeName.TIME, 6),
rexBuilder.makeLiteral("12:34:56.123456"));
final List<RexNode> reducedValues = new ArrayList<>();
executor.reduce(rexBuilder, ImmutableList.of(cast), reducedValues);
assertThat(
((RexLiteral)
reducedValues.get(0)).getValueAs(TimeString.class).toString(6),
equalTo("12:34:56.123456"));
}
{code}
Expected:
{code}
12:34:56.123456
{code}
Actual before the fix:
{code}
12:34:56.123000
{code}
The same issue can occur for TIMESTAMP(6). It can also affect already-created
high precision TimeString/TimestampString RexLiterals if they are passed
through RexExecutorImpl.reduce.
A possible fix is to preserve high-precision temporal literal casts as Rex
literals when they can be represented directly by TimeString/TimestampString,
and to let RexExecutorImpl return existing RexLiteral values without compiling
and executing them again.
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