Copilot commented on code in PR #7944:
URL: https://github.com/apache/ignite-3/pull/7944#discussion_r3045922279
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modules/sql-engine/src/main/java/org/apache/ignite/internal/sql/engine/externalize/RelJson.java:
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@@ -420,7 +420,19 @@ private Object toJson(RexNode node) {
RexLiteral literal = (RexLiteral) node;
Object value = literal.getValue3();
map = map();
- map.put("literal", toJson(value));
+ // Convert the approximate numeric negative zero (-0.0) value
to a string to preserve the minus sign,
+ // otherwise due to USE_BIG_DECIMAL_FOR_FLOATS jackson will
create a BigDecimal from a double (-0.0)
+ // and this will result in the loss of the minus sign.
+ // Other special values +Infinity/-Infinity/NaN are serialized
by jackson as strings.
+ // The value in RexLiteral for approximate types is always of
type Double (see RexLiteral#valueMatchesType).
+ if (value instanceof Double
+ && isApproximateNumeric(node.getType())
+ && ((Double) value == -0.0d)) {
+ map.put("literal", "-0.0");
+ } else {
+ map.put("literal", toJson(value));
+ }
Review Comment:
The negative-zero detection uses `((Double) value == -0.0d)`, but `-0.0d ==
0.0d` is `true`, so this branch will also match positive zero and serialize
`0.0` as the string "-0.0". That would change semantics after deserialization
now that comparisons distinguish +0.0 and -0.0. Use a sign-preserving check
(e.g., `Double.doubleToRawLongBits((Double) value) ==
Double.doubleToRawLongBits(-0.0d)` or `Double.compare(...) == 0` plus raw-bits)
so only negative zero is converted to the string form.
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