[arrow-datafusion] branch master updated: Always increment timer on record (#2298)

[tustvold]

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tustvold pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/arrow-datafusion.git


The following commit(s) were added to refs/heads/master by this push:
     new baa2a367e Always increment timer on record (#2298)
baa2a367e is described below

commit baa2a367ec159992705befc5c735fe3324a83680
Author: Raphael Taylor-Davies <1781103+tustv...@users.noreply.github.com>
AuthorDate: Wed Apr 20 23:39:14 2022 +0100

    Always increment timer on record (#2298)
---
 datafusion/core/src/physical_plan/metrics/value.rs | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/datafusion/core/src/physical_plan/metrics/value.rs 
b/datafusion/core/src/physical_plan/metrics/value.rs
index 4bf92221f..5360f272c 100644
--- a/datafusion/core/src/physical_plan/metrics/value.rs
+++ b/datafusion/core/src/physical_plan/metrics/value.rs
@@ -176,14 +176,23 @@ impl Time {
     }
 
     /// Add duration of time to self
+    ///
+    /// Note: this will always increment the recorded time by at least 1 
nanosecond
+    /// to distinguish between the scenario of no values recorded, in which
+    /// case the value will be 0, and no measurable amount of time having 
passed,
+    /// in which case the value will be small but not 0.
+    ///
+    /// This is based on the assumption that the timing logic in most cases is 
likely
+    /// to take at least a nanosecond, and so this is reasonable mechanism to 
avoid
+    /// ambiguity, especially on systems with low-resolution monotonic clocks
     pub fn add_duration(&self, duration: Duration) {
         let more_nanos = duration.as_nanos() as usize;
-        self.nanos.fetch_add(more_nanos, Ordering::Relaxed);
+        self.nanos.fetch_add(more_nanos.max(1), Ordering::Relaxed);
     }
 
     /// Add the number of nanoseconds of other `Time` to self
     pub fn add(&self, other: &Time) {
-        self.nanos.fetch_add(other.value(), Ordering::Relaxed);
+        self.add_duration(Duration::from_nanos(other.value() as u64))
     }
 
     /// return a scoped guard that adds the amount of time elapsed