Licht-T commented on code in PR #56848:
URL: https://github.com/apache/spark/pull/56848#discussion_r3507249092
##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/DateTimeUtils.scala:
##########
@@ -1287,3 +1298,60 @@ object DateTimeUtils extends SparkDateTimeUtils {
c
}
}
+
+/**
+ * Per-task memoization of a zone's UTC offset, used by the
[[DateTimeUtils.truncTimestamp]] hot
+ * path. The session zone is constant for a query and the offset is
piecewise-constant between DST
+ * transitions, so consecutive rows almost always resolve to the same offset.
The cache holds the
+ * half-open epoch-second interval `[lo, hi)` on which the offset is provably
constant -- derived
+ * from the surrounding zone transitions -- so a lookup that falls in the
interval reduces to two
+ * comparisons instead of a transition-array binary search.
+ *
+ * Not thread-safe by design: a fresh instance is created per task (codegen
mutable state) and used
+ * single-threaded, mirroring how stateful per-row helpers are scoped in
generated code.
+ */
+class ZoneOffsetCache(val zoneId: ZoneId) {
+ private val rules = zoneId.getRules
+ val isFixedOffset: Boolean = rules.isFixedOffset
+
+ private var cached = false
+ private var lo = 0L
+ private var hi = 0L
+ private var offsetSec = 0L
+
+ /**
+ * Offset in seconds at `epochSec`, equal to
+ * `rules.getOffset(Instant.ofEpochSecond(epochSec)).getTotalSeconds`,
memoized over the
+ * constant-offset interval containing the previous lookup.
+ */
+ def offsetSeconds(epochSec: Long): Long = {
+ if (cached && epochSec >= lo && epochSec < hi) {
+ offsetSec
+ } else {
+ val instant = Instant.ofEpochSecond(epochSec)
+ val o = rules.getOffset(instant).getTotalSeconds.toLong
+ if (isFixedOffset) {
+ lo = Long.MinValue
+ hi = Long.MaxValue
+ } else {
+ val nextT = rules.nextTransition(instant)
+ if (nextT == null) {
+ // No transition after `instant`: offset is constant on [epochSec,
+inf).
+ lo = epochSec
+ hi = Long.MaxValue
+ } else {
+ hi = nextT.toEpochSecond
+ // `hi - 1` lies strictly inside the constant-offset window ending
at `hi` (zone
+ // transitions are always more than a second apart), so its previous
transition is
+ // exactly that window's start. Anchoring on an interior point
avoids an off-by-one
+ // when `epochSec` sits exactly on a transition instant.
+ val prevT = rules.previousTransition(Instant.ofEpochSecond(hi - 1))
Review Comment:
`java.time`'s `ZoneRules` stores transition instants as a
**strictly-increasing array of epoch-seconds** (`savingsInstantTransitions:
long[]`), mirroring how TZif / RFC 8536 encodes transition times (a sorted list
of integer seconds). So, the >= 1s gap is always guaranteed. I added this as a
code comment.
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
