Inconsistent AS OF SYSTEM TIME future value behavior

[ecwall]

Actual behavior fails randomly with small AS OF SYSTEM TIME intervals in the future:

[email protected]:26257/movr> CREATE TABLE t();
CREATE TABLE


Time: 3ms total (execution 3ms / network 0ms)

[email protected]:26257/movr> SELECT * FROM t AS OF SYSTEM TIME interval '20 microsecond';
--
(0 rows)


Time: 1ms total (execution 1ms / network 0ms)

[email protected]:26257/movr> SELECT * FROM t AS OF SYSTEM TIME interval '20 microsecond';
ERROR: AS OF SYSTEM TIME: cannot specify timestamp in the future (1667249155.165540000,0 > 1667249155.165537000,0)

Expected behavior: should always fail with any interval > 0.

Happens in master as of 3dd5e68701273a51c076ce4d6835575e9991d8b0.

Jira issue: CRDB-21077

Epic CRDB-17785

[ajwerner]

heh this one is fun :) It's succeeding sometimes because by the time it calls clock.Now 20us have passed.

[ajwerner]

It's at least easy to fix. Maybe something like:

--- a/pkg/sql/sem/asof/as_of.go
+++ b/pkg/sql/sem/asof/as_of.go
@@ -235,7 +235,7 @@ func DatumToHLC(
                }
                // Attempt to parse as an interval.
                if iv, err := tree.ParseDInterval(evalCtx.GetIntervalStyle(), s); err == nil {
-                       if (iv.Duration == duration.Duration{}) {
+                       if iv.Duration.Compare(duration.Duration{}) <= 0 {
                                convErr = errors.Errorf("interval value %v too small, absolute value must be >= %v", d, time.Microsecond)
                        }
                        ts.WallTime = duration.Add(stmtTimestamp, iv.Duration).UnixNano()
@@ -252,6 +252,9 @@ func DatumToHLC(
        case *tree.DDecimal:
                ts, convErr = hlc.DecimalToHLC(&d.Decimal)
        case *tree.DInterval:
+               if d.Duration.Compare(duration.Duration{}) <= 0 {
+                       convErr = errors.Errorf("interval value %v too small, absolute value must be >= %v", d, time.Microsecond)
+               }
                ts.WallTime = duration.Add(stmtTimestamp, d.Duration).UnixNano()