david-mollitor-db opened a new pull request, #58796:
URL: https://github.com/apache/spark/pull/58796
### What changes were proposed in this pull request?
`IntervalUtils.parseNanos` converts the fractional-second digits of a
day-time interval to
nanoseconds. It right-padded the digits to 9 characters with a concatenation
and a substring
before parsing:
```scala
val alignedStr = if (nanos.length < maxNanosLen) {
(nanos + "000000000").substring(0, maxNanosLen)
} else nanos
val nanoSecond = toLongWithRange(nanosStr, alignedStr, 0L, 999999999L)
```
This PR parses the digits directly and scales by the corresponding power of
ten, removing
the intermediate strings:
```scala
val raw = toLongWithRange(nanosStr, nanos, 0L, 999999999L)
val nanoSecond = raw * nanosMultiplier(maxNanosLen - nanos.length)
```
`nanosMultiplier` is a small `10^0 .. 10^8` lookup allocated once.
### Why are the changes needed?
The old form allocated two throwaway strings per call (the concatenation and
the substring)
purely to zero-pad the value ahead of an integer parse. The fractional part
is guaranteed to
be 1-9 ASCII digits by the interval grammar, so it can be parsed and scaled
arithmetically
with no string allocation. JFR profiling of interval parsing attributed
these allocations to
`StringConcatHelper.newString`.
### Does this PR introduce _any_ user-facing change?
No. The result is identical: the parsed value is always in `[0, 999999999]`
and scaling keeps
it within that range, so the range check and error behavior are unchanged.
### How was this patch tested?
Existing `IntervalUtilsSuite` and `IntervalExpressionsSuite` pass; they
cover day-time
interval casting with fractional seconds.
### Was this patch authored or co-authored using generative AI tooling?
Generated-by: Isaac
This pull request and its description were written by Isaac.
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