featzhang commented on code in PR #28146:
URL: https://github.com/apache/flink/pull/28146#discussion_r3228490257
##########
flink-table/flink-table-common/src/main/java/org/apache/flink/table/expressions/ValueLiteralExpression.java:
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@@ -462,11 +462,18 @@ private static String serializeTimestampLtz(Instant
instant, int precision) {
/**
* Checks whether an {@link Instant} can be represented as a {@code long}
epoch value at the
- * given precision without overflow.
+ * given precision without overflow. Accounts for the sub-second nanos
term that {@link
+ * DateTimeUtils#toEpochValue} adds on top of {@code epochSeconds *
10^precision}.
*/
private static boolean canRepresentAsLong(Instant instant, int precision) {
- long factor = (long) Math.pow(10, precision);
- long epochSeconds = instant.getEpochSecond();
- return factor == 0 || Math.abs(epochSeconds) <= Long.MAX_VALUE /
factor;
+ final long factor = (long) Math.pow(10, precision);
+ final long nanoDivisor = (long) Math.pow(10, 9 - precision);
+ final long epochSeconds = instant.getEpochSecond();
+ final long nanoPart = instant.getNano() / nanoDivisor;
+ if (epochSeconds > Long.MAX_VALUE / factor || epochSeconds <
Long.MIN_VALUE / factor) {
+ return false;
+ }
+ final long base = epochSeconds * factor;
+ return base < 0 || nanoPart <= Long.MAX_VALUE - base;
Review Comment:
The short-circuit for negative base is correct but might benefit from a
comment for clarity:
```java
// Negative base + non-negative nanoPart moves toward zero, can't overflow
upward
return base < 0 || nanoPart <= Long.MAX_VALUE - base;
```
Since `nanoPart >= 0` always (from `instant.getNano() / divisor`), adding it
to a negative base can't exceed `Long.MAX_VALUE`.
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