sql/ttl: use AOST timestamp when computing query bounds

Previously, when computing query bounds from spans in the TTL job
processor, we used the current timestamp for the KV Scan/ReverseScan
operations. This could cause contention with foreground traffic.

This change updates the TTL processor to use the same AOST (As Of
System Time) timestamp for computing query bounds that is already
used for the SELECT queries. This aligns the bounds computation with
the historical time at which the TTL job operates, reducing load on
the system and improving overall efficiency.

Resolves: #155871
Epic: CRDB-55074

Release note: None

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: rafiss

pkg/sql/ttl/ttljob/BUILD.bazel

@@ -47,7 +47,6 @@ go_library(
         "//pkg/sql/types",
         "//pkg/util/admission/admissionpb",
         "//pkg/util/ctxgroup",
-        "//pkg/util/hlc",
         "//pkg/util/log",
         "//pkg/util/metric",
         "//pkg/util/metric/aggmetric",

pkg/sql/ttl/ttljob/ttljob_processor.go

@@ -34,7 +34,6 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/sql/types"
 	"github.com/cockroachdb/cockroach/pkg/util/admission/admissionpb"
 	"github.com/cockroachdb/cockroach/pkg/util/ctxgroup"
-	"github.com/cockroachdb/cockroach/pkg/util/hlc"
 	"github.com/cockroachdb/cockroach/pkg/util/log"
 	"github.com/cockroachdb/cockroach/pkg/util/quotapool"
 	"github.com/cockroachdb/cockroach/pkg/util/retry"
@@ -298,6 +297,10 @@ func (t *ttlProcessor) work(ctx context.Context, output execinfra.RowReceiver) e
 		// Iterate over every span to feed work for the goroutine processors.
 		kvDB := db.KV()
 		var alloc tree.DatumAlloc
+		// Compute the AOST timestamp for SpanToQueryBounds. This aligns the bounds
+		// computation with the historical time used by the SELECT queries, reducing
+		// contention with foreground traffic.
+		aostTimestamp := kvDB.Clock().Now().AddDuration(ttlSpec.AOSTDuration)
 		for i, span := range ttlSpec.Spans {
 			if bounds, hasRows, err := spanutils.SpanToQueryBounds(
 				ctx,
@@ -309,7 +312,7 @@ func (t *ttlProcessor) work(ctx context.Context, output execinfra.RowReceiver) e
 				numFamilies,
 				span,
 				&alloc,
-				hlc.Timestamp{}, // Use current time bounds; TTL only deletes live rows.
+				aostTimestamp,
 			); err != nil {
 				return errors.Wrapf(err, "SpanToQueryBounds error index=%d span=%s", i, span)
 			} else if hasRows {